How do you get 3-Phase power to a residential workshop

[Alan Lightstone]

Can you get 3-phase power directly from the utility company, or must you use a rotary phase converter or a VFD?

Does a VFD replace a rotary phase converter (does it convert 1-phase to 3-phase), or do you just use it to control the power of already delivered 3-phase power?

[Martin Wasner]

Depends on proximity and how much you want to spend getting it there. Residential use will be very low, so if they'll do it, it's going to cost a fortune.

I use a fair amount of juice and had to go 1200 feet, I budgeted $20,000 but ended up paying less than $5000 with a transformer

[Martin Wasner]

And yes, a vfd can make 3 phase from single phase

[Alan Lightstone]

And yes, a vfd can make 3 phase from single phase
From my quick research, it seems like vfd's max out at about 1.5HP. I will need 220V 3-Phase for a few 5HP 3-phase motors (jointer, planer, table saw). They shouldn't be running at the same time.

What's the best approach for that? A Rotary Phase Converter, A Digital Phase Converter like the Phase Perfect model? Another approach?

[Dan Friedrichs]

You can get larger VFDs. If you look on ebay, you can find 5HP single-phase-input VFDs for ~$180.

[Bill Dufour]

For big tools like those you can power them from one VFD running one motor at a time. Not too hard if they are the same amp draw motors if you do not care about the instant reverse, variable speed, braking or low speed start up being custom tuned for each tool.
That extra stuff is really only needed for a drill press or maybe a sander or lathe.
Bill

[Alan Lightstone]

Interesting. The VFDs even the 10HP ones on eBay (I will need a 10HP one for a 5HP motor, right?)are much less expensive than I expected.

Are they difficult to program. I'm concerned as the units are Chinese, inexpensive, and may not have awesome English instructions.

[Bruce Wrenn]

VFD's are available in the 6000 HP range (think railroad locomotives,) but you can't afford them. A rotary converter is the best way to go for multiple machines. It's basically a three phase motor, with a method of bring it up to speed. Generated third leg is usually a little lower than other two legs.

[Matt Day]

Alan, lots of information on VFD's on here so please do some homework, though of course we're here to help.

Factorymation products are solid and have great manuals and great customer support. You'll pay a bit more than eBay models from overseas, but if you're not comfortable it may be worth it.

[David Kumm]

You can get into a RPC for 1000-1500, vfds will run 250-400 for each machine and require you to bypass most starters and wire the start stop buttons to the vfd. Not a huge deal but sounds like you don't have a lot of experience with them so you would need some help. Phase Perfect is a close to perfect option but will cost you about 4000. Power will be balanced much better for all sizes of motors. With an RPC the quality of the motor and electrical components will account for the price differences among the brands. Kay and Arco rate their units by the largest motor it will start. Most others rate them by the total hp they will run. A 10 hp Kay is roughly equal to a 20 hp Am Rotary as an example. Important to know that when comparing pricing. You want to slightly oversize them. A 7.5 hp Kay or 15 hp AM Rotary. That size rpc will be best balanced at higher loads but still run small motors. With VFDs pay attention to the output amperage. You need 15+ amps for a 5 hp motor. Some will be rated at 5 hp and some at 10 hp but the output amps are the key. Dave

[Bill Dufour]

Some vfd's are full rated output on single phase input. others are derated to 75%. Even with true three phase a VFD is a good thing on drill presses etc. where variable speed is nice to have.
Bill D

[Bobby A Thompson]

Working on restoring a covel surface grinder. I am using a Teco Drive like these http://www.factorymation.com/acdrives

[Steve Jenkins]

Before getting into converters contact your utility and see about availability of 3 phase. You might find though that under no circumstances will they provide it to a residence. I went the rotary route and installed a 3 phase panel fed by the converter. I have a Kay and have had no problems in 12 years of commercial use.

[jack forsberg]

Can you get 3-phase power directly from the utility company, or must you use a rotary phase converter or a VFD?

Does a VFD replace a rotary phase converter (does it convert 1-phase to 3-phase), or do you just use it to control the power of already delivered 3-phase power?

vFD's were generally develop for three phase power and only in recent years have they been used for single phase conversion. They initially were never designed for that it just so happen they can do that . About eight years ago single phase input drives appeared on the market to accommodate single phase strictly . The first ones were both single and three phase input . Generally these went to three horse power and not much larger .

A few years ago I worked in conjunction with a large manufacture and I'm having single phase input VFD's custom made for woodworking machinery and specifically for single phase input . This means that the parameters for the drive are for single phase purposes and outputs are proper for the drive size . My drives are not the derated.
I supply drives up to 15 hp single phase input . Our single phase 5 Horse Drive is $275 plus shipping . And that includes walking you through step-by-step on getting it set up in your machine running . These are state of the art drives . If you go to "Jack English machines " on you tube there's a playlist and contact information if you're interested. You can generally run approximately 50 horse power off a residential service .

[Bill Adamsen]

What Dave said.

Also, economic savings by planning to move a single VFD from machine to machine would be challenging and not especially extensible though certainly it has been done. The key benefit would be cheaper wiring, either a high(er) amperage single-phase 220v or extension cord. Programming would need to be consistent which might be more challenging. You would need to program your VFD to allow storing different sets of criteria ... ramp up, slow down, jog ... for each machine. Or use criteria applicable to all the machines.

Also, VFD typically come in an IP20 or possibly NEMA 1 enclosure. If you feel your environment requires greater protection than that (likely) you'll need to plan accordingly and that can get expensive. So for instance, the popular Teco FM50 comes available in IP20 as a 3hp unit (the FM50-203C) for about $200 or as a NEMA4 (FM50-203-N4FS) for $500. The recommended volume for a VFD in a NEMA 3 puts buying that separately as a not inconsequential cost. All that starts to make the RPC more attractive.

[Dan T Jones]

I have been using a 5hp RPC from these folks for about 3 years. I also had 3 3 phase machines. I bought a used 3 hp motor on ebay for $60 and was in business.
https://phaseconverterusa-com.3dcartstores.com/crm.asp?action=contactus
Dan

[Malcolm McLeod]

Can you get 3-phase power directly from the utility company, or must you use a rotary phase converter or a VFD?

Does a VFD replace a rotary phase converter (does it convert 1-phase to 3-phase), or do you just use it to control the power of already delivered 3-phase power?

You can get 3-phase power from the utility company. It is the standard in most industrial and/or business areas. Cost will vary greatly, depending on where you are: Is there 3-ph on the pole serving your property? Or is it 16 miles away, with a 1-ph branch line and feeder to your property? If it's close, is there a 3-ph transformer with it? Is it overhead or underground?

As others have said a VFD can replace a RPC, and a VFD can convert 1-ph to 3-ph. A VFD can also be used with a RPC (or 3-phase service) to control the speed, direction, and accel/decel/braking of a motor.

Why are VFDs de-rated he asked? (NOT) :confused:

A 5Hp/230V/3ph motor typically draws ~15FLA per phase. A VFD for this motor would have its internal components sized to handle this 15A (plus some margin of safety).
A 5Hp/230V/1ph motor typically draws ~28FLA per phase. A VFD for this motor has to have larger internal components to deal with the increased amperage. Lo and behold, a 10Hp/230V/3-phase motor draws ~28A, so you buy a 10Hp (3ph) VFD and use it for the 5Hp (1ph) motor. VFD is magically 'de-rated'. Edit: I should add that in this example the input section of the VFD handles 28A (1ph), and the output section handles 15A (3ph) - - both sections are handling the requisite 5Hp.


But this is old news. As Jack points out, manufacturers have begun to respond to the demand for 1ph VFDs and they will specify the HP/Amps/phasing that a given model will support - no user derating needed. Just read the specs before you buy.

[Tom Trees]

I got another VFD recently, I thought I was getting another Huanyang 3HP, but it happens to be an askpower/isacon drive.
Previous drive died because I stalled the motor on my bandsaw for far too long....I was really taking the pi**:(
I ended up needing the front panel board anyway, as the other Huanyang VFD had an issue with the relay after disconnecting it to test out another motor.

These Isacon/Askpower drives don't have the terminals for a braking resistor like the Huanyang does (although the Huanyang VFD's still need parts soldered on the board for a braking resistor to work)...
Also unfortunately, these newer drives need a relay aswell for a separate start and stop switch to work (3 wire control)

Another thing is, these have the same shutoff feature with the fan as your drives does Jack ...
I came into my shop yesterday to see that I had left it on for nearly two days :rolleyes:
I keep the humming VFD for the tablesaw, as the bandsaw is a bit more of a now and again tool.

Funny, I find the Huanyang noisy and slightly irritating, but I find the quiet one scary if you forget it's on....
I should really get a relay, so I can use the emergency twistlock switch again :eek:

BTW These newer Isacon/Askpower drives have a blue sticker on the panel, and have tabs on top for opening up the casing.
368327368328368329


So can a 5HP VFD run a 5HP motor ...I was told you need a 10HP one aswell ?

Tom

[Malcolm McLeod]

~~~ So can a 5HP VFD run a 5HP motor ...I was told you need a 10HP one aswell ? ~~~

It depends...
Certainly if a VFD is rated for 5Hp at 230V/3ph, then it will run the equivalent motor if supplied with 3ph power. Each phase will pull up to 15FLAmps, and each component in the VFD is sized for this - inputs and outputs.

If the VFD is rated for 5Hp at 230V/3ph and you supply 230V/1ph to it, then you are feeding up to 28FLAmps thru a set of components in the VFD that are sized to handle only 15A. Magic smoke may emerge.

If a manufacturer rates a VFD for 5Hp at 230/1ph, then you can probably rest assured that each component string in the VFD's input section will safely handle 28FLA. The output section may be sized for 3ph (::15FLA). The output might even be sized to handle the full 28A on any leg (for a 1ph motor) - - but I am getting out of my comfort zone here - - so again, read the mfgr's spec carefully.

[Martin Wasner]

Magic smoke may emerge.


The Prince of Darkness, aka Lucas Electronics, has your back.


http://www3.telus.net/bc_triumph_registry/images/Smokekit2.jpg

[Malcolm McLeod]

The Prince of Darkness, aka Lucas Electronics, has your back.


http://www3.telus.net/bc_triumph_registry/images/Smokekit2.jpg

ROFL..... I need 2!

[Matt Day]

The Prince of Darkness, aka Lucas Electronics, has your back.


http://www3.telus.net/bc_triumph_registry/images/Smokekit2.jpg

Could you post a link where I can buy that?






;)

[Alan Lightstone]

So if I'm understanding this right:

1.) A single, properly sized rotary phase converter can be used to supply all the 3-phase equipment in the shop (with one device being used at a time) assuming it is sufficiently sized to handle the capacity (roughly twice the 5HP max I will need to enable the starting motor surges, or a 10HP unit).
2.) VFDs do exist that can handle the 5HP equipment, but I would likely need one per tool, each programmed separately.
3.) Jointers, Planers, Bandsaws, and Table saws do not need the variable speed adjustment that a VFD could provide.
4.) Rotary Phase converters include large motors, so will be loud themselves, in addition to the tools they power. VFDs are quieter (is this true??)
5.) 3-phase power to the residential home is likely to not be available, or potentially extremely expensive to obtain. (I'll have to check with utility about this).

[Malcolm McLeod]

So if I'm understanding this right:

...
2.) VFDs do exist that can handle the 5HP equipment, but I would likely need one per tool, each programmed separately.
3.) Jointers, Planers, Bandsaws, and Table saws do not need the variable speed adjustment that a VFD could provide.
4.) ... VFDs are quieter (is this true??)
...


Answers that I know:
2. Correct, but it is very likely that one could service all the typical home shop equipment - especially if of similar Hp. Put a receptacle on the output and plug in the chosen tool; just don't swap loads while the VFD is powered.
3. Probably true, but all can benefit from the accel/decel ramp available in a VFD. YMMV
4. Full disclosure - VFDs typically cause a motor to produce a harmonic hum or whine that some may find bothersome (I can't compare to RPC noise, since I don't RPC:confused:).

[Brad Shipton]

I don't follow why you want three phase for 5hp motors. Usually when you start buying used industrial machines they are in the 9hp+ range (big shapers, 10' sliding table saw, 16"+ jointer, 24" planer). Then you are beat. If you are buying used equipment with 5hp motors you could swap out the motors for what all the headache you will start with a VFD. My 10hp CNC spindle has a Mitsubishi VFD and I think it was $2k before installed.

[Alan Lightstone]

I don't follow why you want three phase for 5hp motors. Usually when you start buying used industrial machines they are in the 9hp+ range (big shapers, 10' sliding table saw, 16"+ jointer, 24" planer). Then you are beat. If you are buying used equipment with 5hp motors you could swap out the motors for what all the headache you will start with a VFD. My 10hp CNC spindle has a Mitsubishi VFD and I think it was $2k before installed.
Equipment that I'm looking at includes a Felder A941 Jointer (standard 3-phase, 5.5HP motor), Felder D951 Planer (standard 3-phase, 5.5HP motor), Felder FB710 Bandsaw (3-phase 7.5HP motor), Sawstop ICS (3-Phase 5HP motor - although available as 1-Phase 5HP). Other pieces of equipment are 1-phase.

I can get some, if not most of that equipment with less powerful 1-phase motors, but why???

[David Kumm]

Will the planer have a power table up and down? that would require a second vfd. for the machines you mention, I'd go rpc or PP. The electricals on Euro machines are a little more complicated to bypass and there may be motor brakes as well. I'd rather have the 7.5 hp motor on the 20" planer ( especially if the silent power head ) than the bandsaw but that is just me. Once you go three phase you will never really like single phase again. Dave

[Phil Gaudio]

I am going to go out on a limb here and say that (assuming you have overhead service in your area) if you look at the utility poles near your house and see 3 lines across at the very top, you are in good shape for potentially getting 3 phase. if you see only a single line:fugetaboutit.

[John Lanciani]

Equipment that I'm looking at includes a Felder A941 Jointer (standard 3-phase, 5.5HP motor), Felder D951 Planer (standard 3-phase, 5.5HP motor), Felder FB710 Bandsaw (3-phase 7.5HP motor), Sawstop ICS (3-Phase 5HP motor - although available as 1-Phase 5HP). Other pieces of equipment are 1-phase.

I can get some, if not most of that equipment with less powerful 1-phase motors, but why???


If I were in the fortunate position to be considering that list of equipment I would be looking at a PhasePerfect and nothing less. Buy once, cry once, and never have to worry about it again. Put in a 3 phase breaker panel on the load side of the PP and you're in the big leagues.

[Brad Shipton]

I follow you now, and I am guessing the change in budget will be fine once you get past the sticker shock. Did you ask Felder for a recommendation? I agree with David about 7.5hp for the planer. Beyond that, I will leave the electrical questions to others.

That is a nice list of machines.

[David Kumm]

I used a Kay RPC for years and it was fine but the swap to a PP was a real upgrade. Legs are balanced within 2% or less which is way better than an rpc. Virtually no noise other than a little sizzle. A 10 hp PP will start a higher hp motor than a similar sized rpc. Similar to a RPC, you don't want to run the manufactured leg through the controls. A PP is a delta output so the mfg leg measures 208 to ground. Dave

[Alan Lightstone]

Have to check into the 7.5HP motor for the planer. (You guys are killing me...:))

No utility poles to look at (thankfully, considering the issue of hurricanes down here...)

So you're suggesting one PhasePerfect going to a breaker panel, then normal 220V, 3-Phase outlet wiring to each load.

Those machines won't have to have different programming for each of them?

[Alan Lightstone]

I used a Kay RPC for years and it was fine but the swap to a PP was a real upgrade. Legs are balanced within 2% or less which is way better than an rpc. Virtually no noise other than a little sizzle. A 10 hp PP will start a higher hp motor than a similar sized rpc. Similar to a RPC, you don't want to run the manufactured leg through the controls. A PP is a delta output so the mfg leg measures 208 to ground. Dave
Is 208 to ground an issue with the machines?

[Martin Wasner]

Is 208 to ground an issue with the machines?

I'm not sure I follow, so this might be outta left field.

Depends on the machine. Most 208/230 is fine. Some are picky and require parts. Some require too many parts to change voltage to be cost effective. My panel saw is 208 only and the importer said it's a giant pia to change voltages on. Not just switching taps in the doghouse. The bulk of equipment is just a matter of switching taps on the motor and in the transformer for control power. You may have to adjust any it overloads it has too. Most stuff it's pretty simple because the machine is simple.

Like Darcy said, it's nice having 480 on the pole. You can do whatever you want at that point.

[Alan Lightstone]

Similar to a RPC, you don't want to run the manufactured leg through the controls. Dave
Could you please explain this in more detail? I don't understand what a manufactured leg is, and which controls you are referring to.

Thanks. I've been learning tons here. Hopefully many others as well.

[Mike Heidrick]

Study the wiring diagram of the machines you are running to determine if the control circuit needs to not be on the generated leg of a converted setup. My new dust collector was like this. I standardized my wiring to use the white wire and middle bar and middle leg of tje 3ph breaker in the panel powered by the generated leg so I always know which lead is generated. Most control circuits are wired though l1 or l3 so having generated on 2 is a typical wiring solution. Again you need to understand what you are wiring and what the requirements are.

I have several makes and models of vfd and also a couple rpcs. 20hp rpc in new shed and 5hp rpc in old. Big PP's are pricey. I am prepped to move tp one someday.

Dont forget wiring costs in your plans. Check your converters specs for proper wiring.

I am also a fan of various dif low voltage methods to start your converter.

[Chris Parks]

Equipment that I'm looking at includes a Felder A941 Jointer (standard 3-phase, 5.5HP motor), Felder D951 Planer (standard 3-phase, 5.5HP motor), Felder FB710 Bandsaw (3-phase 7.5HP motor), Sawstop ICS (3-Phase 5HP motor - although available as 1-Phase 5HP). Other pieces of equipment are 1-phase.

I can get some, if not most of that equipment with less powerful 1-phase motors, but why???

Why not? As a (I presume) hobbyist the single phase will do the job and three phase will in all likelihood make selling the used machines harder and possibly reduce their market value. I used to sell VFD's with Clearvue Cyclones in Australia as that was the only way we could power the motor here so I have seen the advantages and disadvantages of what you propose. I also have had and still own three phase machines for woodworking and for a hobbyist I can't see the advantage for saws, planers etc. If the hobbyist wants to use old antique machines then a VFD is the simple and quick answer but where the machine can be supplied in either form single phase is less complicated and re-sale is easier.

I get emails weekly form Chinese companies trying to flog me VFD's and I ignore them all. We tried Huanyang initially and then went to Powtran because at the time Huanyang became unavailable and also the fact that factory support from Huanyang did not exist and there was confusing documentation being supplied. Powtran are a way better unit at the lower end of the market and I have field tested hundreds of them with only two failures after many years of service. They also do a mini VFD that is ideal for a drill press if anyone is interested.

[Frank Drew]

I got 3-phase directly from the utility company but I was lucky that my shop was only 100 feet or so from the lines carrying it so I didn't have to pay a distance premium. Even though mine was a commercial shop, I still had to submit a "load letter" detailing the equipment with motor sizes I'd be installing -- they had a minimum h.p. requirement for 3-phase hookups.

[Joe Jensen]

We are moving to a new home on a large lot in a custom home neighborhood. When I called the utility to see how large a service I could get the engineer asked what I would be running in the shop. Told him a large welder, 10 ton heat pump, 10HP compressor, 10HP dust collection, etc, etc. He then looked at the lot drawing and found that I have 3 phase running under my east property line. Net net I will be able to get 400A of utility 3 phase for $3400 to cover the installation of two transformers.

[David Kumm]

Low voltage three phase will either be 208 which has each leg rated at 120v to ground or 240 delta. 240 three phase will be referred to as delta and have two legs measure 120 to ground and the third will measure 208. That is typical and every 220-240v machine will run on 240 delta. The only issue is not to run the 208 manufactured leg to the controls or internal voltage transformer. Most Euro machines run 120 controls and use a transformer internally to convert the many voltages used wordwide to a standard 120 or perhaps 24v. A RPC generates a high voltage leg too. Most high voltage three phase ( 480-600 ) will be Wye rather than delta to have a better ground for the higher voltage. Most of this isn't relevant unless stepping voltage up from 240 to something higher. Most machines rated 208 can handle 240 unless the utility supplies power higher than 240. Then some will buck the voltage down. Remember the voltage to ground isn't all that important. How it balances out between the three legs is. The PP is best at that. Dave

[Joe Calhoon]

Dave, my incoming 3 phase has the wild leg as you describe. We have always kept that leg off the control side and never any issues. Even with CNC machines. We have a couple 480 volt machines on step up transformers and coming out of the transformer all legs measure the same. Not knowing much about electricity I have never understood how this happens and if I should worry about what leg is going to the control side. Again no issues with the machines connected to the transformers.

For years we ran several 5 to 10 hp 3 phase machines off a home built converter made from a heavy 15hp motor we picked up for almost nothing from a local mine. Had to spin it up with a small motor and belt but once it got to speed it started right up. It was a crude setup but worked for several years and seemed to run all the machines with no loss of power. If I ever get into a retirement shop Phase Perfect will be the way to go.

[Darcy Warner]

It has been so nice over the last year and a half having real 480v Wye pole power. One big transformer for 240v 3phase and one smaller one for my single phase is so much nicer than running a rpc.

[jack forsberg]

Low voltage three phase will either be 208 which has each leg rated at 120v to ground or 240 delta. 240 three phase will be referred to as delta and have two legs measure 120 to ground and the third will measure 208. That is typical and every 220-240v machine will run on 240 delta. The only issue is not to run the 208 manufactured leg to the controls or internal voltage transformer. Most Euro machines run 120 controls and use a transformer internally to convert the many voltages used wordwide to a standard 120 or perhaps 24v. A RPC generates a high voltage leg too. Most high voltage three phase ( 480-600 ) will be Wye rather than delta to have a better ground for the higher voltage. Most of this isn't relevant unless stepping voltage up from 240 to something higher. Most machines rated 208 can handle 240 unless the utility supplies power higher than 240. Then some will buck the voltage down. Remember the voltage to ground isn't all that important. How it balances out between the three legs is. The PP is best at that. Dave
The reason PP has 208 to neutral is because the two single phase legs are not going through refractors. But I really don't understand what the relevance of the two 208 to neutral would be anyway because the machines are wired Delta and the coils would never receive a Y connection with neutral . The problem with rotary phase is the drop of voltage on the wild leg but this is guaranteed to with in 2 percent with phase perfect still though you would never feed from that side . I'd always wondered how this was possible to have 208 to ground until I looked into it . and it must be that phase perfect is only generated one phase . So it's kind a like a glorified single phase leg VFD without variable frequency .

A VFD would be 240 Leg to leg and 120 ground on all three but then single phase power would never be derived from the three phase out put side anyway to control voltage transformers because the VFD is the controller And single phase is available on the primary side . So I say the VFDs have the upper hand over phase perfect in regards to inductive loads . I also think for the money one can supply himself with far more horsepower money wise and then be on a more reliable system because only a single machine can go down if there is a system failure . The phase perfect is great at stepping up voltage with transformers and are the cats behind in supplying power for welders and lighting but in the 240 volt range I find it hard to stomach the cost of phase perfect to run motors . Just a hobby for me too Dave

[David Kumm]

Yes Jack, the PP is generating only one leg. The high leg in 240 delta. Same as when a utility delivers high leg delta three phase. I'm a fan of vfds too but when you have lots of machines ranging from 1/2-25 hp, there is only one unit that can handle all of them well and that is PP. There also doesn't seem to be any issues related to motor insulation of bearing fluting which, although rare, can happen with vfds. Dave

[jack forsberg]

Yes Jack, the PP is generating only one leg. The high leg in 240 delta. Same as when a utility delivers high leg delta three phase. I'm a fan of vfds too but when you have lots of machines ranging from 1/2-25 hp, there is only one unit that can handle all of them well and that is PP. There also doesn't seem to be any issues related to motor insulation of bearing fluting which, although rare, can happen with vfds. Dave
I'm not convinced at all that there are issues with leaking voltage at 240 V that cause a new bearing failure . Also a 25 horse power machine in a shop running on single phase would be the envy of the neighborhood . I still think I could supply these horsepowers for cheaper than phase perfect and be more reliable . In the last few years I've read of two units that have exploded .
VFDs will certainly handle inrush current way better and in so doing not dim my neighbors lights . Still for the majority operating from single phase power 15 horse power is really large . I can give you a vfd for that $1000 . Phase perfect will be well over three times that . So for A four head moulder running 15 hp heads total 45 hp I can set you up for four grand . I'd be sitting down for the price on phase perfect. I think up at these range the rotary phase converter still has a place economically . What I will say is phase perfect makes it easier for one to plug in a machine they acquisition . Are you saying that you have a four wire delta coming out of phase perfect and that A and B are tapped at 208 or is it just a 3 wire system with no neutral .

[David Kumm]

Jack, the PP has only one 208 to ground leg so just like high leg delta. I agree with all you say. Vfds are great and cheaper until you need about ten of them. When you have several high hp machines, a rpc or pp both become reasonable when compared to the utility alternative. Two smaller rpc that can be run separately or together can solve some of the imbalance issues over a wide hp range too. Several ways to solve the same problem. I run all three types and all have a place. Like you, I'm usually a used guy but if looking for a used PP you want the newer white ones. The blue ones are no longer supported so buy them cheap. Dave

[jack forsberg]

Jack, the PP has only one 208 to ground leg so just like high leg delta. I agree with all you say. Vfds are great and cheaper until you need about ten of them. When you have several high hp machines, a rpc or pp both become reasonable when compared to the utility alternative. Two smaller rpc that can be run separately or together can solve some of the imbalance issues over a wide hp range too. Several ways to solve the same problem. I run all three types and all have a place. Like you, I'm usually a used guy but if looking for a used PP you want the newer white ones. The blue ones are no longer supported so buy them cheap. Dave Dave just to make sure you understand I'm not arguing with you I actually just like tossing back-and-forth with someone who knows what they're talking about .

Let's compare multiple VFD's with Phase perfect . And then all talked about the features . I'm going to pick their most common 10 hp unit that outputs 36 A continuous . Cost $3390 now this can generally run a whole shop but it will only out put that amount continuously but will allow you to run multiple machines at the same time so let's assume this is a small shop and at most will have 8 to 10 machines running at once which I would find very generous . I'll assume that we will need to start a 10 hp motor as well . I will also assume that the maximum output in single phase would be a 200 amp service . The 10 hp face perfect will need approximately 60 to 70 A well below the 80% load calculation of the 200 amp service which would be 160 A . This is a nice one because it also fits in the 80 percent load allowance on 100 amp service probably most common in single phase shops .


Just to correct the miss conception they have on their site that VFD's cannot run multiple motors Will assume they're right but they're not and only supply of VFD per motor .
The 10 hp VFD is $750 but let's take two of them just in case you have 2 10 hp motors that you want to start at the same time . Let's take one 7 1/2 hp at $500 and 4 5 hp's at 275 , 3 3hp at 215 and a 2 hp at 185 total cost of $3430 total hp 58.5 will over a 200 amp Service . That's 11 drives with 7 of them 5 hp and larger including two that are 10 hp. I would say this is a fairly ambitious single phase shop . It's late and I missed $500 but I think you get the point .

[Chris Hachet]

At some point I think a nice high end phase converter is inevitable if you run a lot of three phase equipment in a single phase wired shop.

That being said, I freaking adore three phase motors and how well they run. Psychologically, it is worth running VFD's just for features like soft start and motor protection for me...even though I am very aware of how well regular motor starters protect 3 phase motors.

At some point, I see having both some sort of phase conversion and VFD's.

[Bradley Gray]

I run 11 3 phase machines with 2 RPC's - a homemade 7hp and a Kay 10hp

I ran all of it from the 7hp for many years and added the Kay a few years ago. My big planer and face jointer showed a huge improvement in power when i added the 10hp Kay.

The simplest converter I ever saw was in a big machine shop full of old iron machine tools - a big idler motor that the toolmaker spun up in the morning using his foot on the idler pulley!

[Malcolm McLeod]

... just like tossing back-and-forth ... ... correct the miss conception they have on their site that VFD's cannot run multiple motors ...

At the risk of going completely off the rails from the OP's original question, most of my VFD experience has involved commissioning them in industrial environments. I have heard of sheeting line installations with a single large VFD operating 50-some-odd motors (1/2Hp? - - IIRC). Clearly a VFD is capable of operating more than one motor at a time. It simply requires an understanding of the required controls for the respective motors: each motor should have independent OL protection; and probably a means to isolate it (a contactor or just unplug).

I have personally worked on the controls for a production line with 12-15 VFDs. Each VFD 'system' used a single VFD which was multiplexed to 5 different motors. The operator used a rotary selector switch to connect a given motor to the VFD (via individual contactors), then used up/down switches to make fine adjustments to the mechanism of the respective motors. In this case, the motors were all similar Hp, so used the same built-in OL protection of the VFD. The original designer's code allowed the VFD to 'start' before confirming the selected contactor was closed; thus the motor 'slammed' into a VFD output that was already well above zero - - result was almost always a VFD fault. (I was called in to identify the problem and fix it.)

The latter case is why I have repeatedly cautioned here about powering down a VFD before swapping to another motor. It is not strictly necessary to power down, but it IS certainly safer for both people and equipment. The VFD should absolutely be completely stopped before connecting/disconnecting anything on the output side!

When I saw the OP's drool-worthy list of equipment, I considered that VFD(s) are probably not the most cost effective solution, but Jack certainly makes a case for such. Especially if like-Hp equipment can share a VFD (and thus the OL protection afforded by the VFD). Or, get a large VFD - capable of operating 2-3 machines likely to be running simultaneously - and let them share the same accel ramp, speed setpoint, and decel ramp, but use separate OL protection for each machine. ...Food for thought?

[David Kumm]

This is a good discussion. There should be multiple ways to deal with how to power machines. There is some programming skill involved when going the all vfd route. My home shop has 20+ three phase machines, six of which are on vfds. the largest is the DC at 7.5 hp. Dust collection is a no brainer for a vfd. The only machines that run at the same time would be the DC and a 5 hp air compressor on a pressure switch in addition to the main machine. At least four of the other machines have multiple motors and some have injection brakes as well. You certainly could program a few vfds with remote keypads to run the machines. While I can do some wiring and handle the circuit needs of an rpc and pp, I would need help programming and bypassing that many machines, some simple, some complicated. If I have to pay for that help, the PP starts to make economic sense ( although one of two rpc are still cheaper ). Since I have more money than time and I found a NOS PP for 2K, the decision was easy. I also run a 30 hp PP in my storage building shop and I was willing to pay full price for it. Dave

[Warren Lake]

old school here had a friend with a big motor and a pull cord to start it. I bought a built roto pro company maybe 30 years ago 10 HP ran and started 10 HP and there were two heavier options available. 10 HP could run 3 times that total and you were supposed to start motors in a certain order. I think a smaller one before your 10 HP Max one. Running more motors made the whole thing more efficient as they somehow act as ballasts for each other. Total amperage was less than what you were running no idea how that ballast thing works. Not to go sideways but never see people comparing what is drawn from the different ways of running stuff. Id assume VFD's are cheaper to run as there is no motor to turn over then there is no ballast affect whatever that is and how it works.

[jack forsberg]

At the risk of going completely off the rails from the OP's original question, most of my VFD experience has involved commissioning them in industrial environments. I have heard of sheeting line installations with a single large VFD operating 50-some-odd motors (1/2Hp? - - IIRC). Clearly a VFD is capable of operating more than one motor at a time. It simply requires an understanding of the required controls for the respective motors: each motor should have independent OL protection; and probably a means to isolate it (a contactor or just unplug).

I have personally worked on the controls for a production line with 12-15 VFDs. Each VFD 'system' used a single VFD which was multiplexed to 5 different motors. The operator used a rotary selector switch to connect a given motor to the VFD (via individual contactors), then used up/down switches to make fine adjustments to the mechanism of the respective motors. In this case, the motors were all similar Hp, so used the same built-in OL protection of the VFD. The original designer's code allowed the VFD to 'start' before confirming the selected contactor was closed; thus the motor 'slammed' into a VFD output that was already well above zero - - result was almost always a VFD fault. (I was called in to identify the problem and fix it.)

The latter case is why I have repeatedly cautioned here about powering down a VFD before swapping to another motor. It is not strictly necessary to power down, but it IS certainly safer for both people and equipment. The VFD should absolutely be completely stopped before connecting/disconnecting anything on the output side!

When I saw the OP's drool-worthy list of equipment, I considered that VFD(s) are probably not the most cost effective solution, but Jack certainly makes a case for such. Especially if like-Hp equipment can share a VFD (and thus the OL protection afforded by the VFD). Or, get a large VFD - capable of operating 2-3 machines likely to be running simultaneously - and let them share the same accel ramp, speed setpoint, and decel ramp, but use separate OL protection for each machine. ...Food for thought?

Honestly I don't even think it's that complicated as an example a planer with a cutter block and feed motor running off phase perfect would have no speed control or over load or anything, it's simply is used as phase conversion. Child's play for a VFD . The VFD needs to actually just be sized for full load amps of both motors . Motors are started simultaneously under similar parameters regardless of their kW in regards to phase conversion . Parameters for overload would just be run in the stop control switches control side using heater blocks most likely already existing in the machine . Running these simply in the series with stop control switches from 3 wire control . The biggest issues with multiple motors is bringing them on line not disconnecting them . But woodworking machinery in generally are not that way . Still VFDs are so cheap why not go beyond just the phase conversion feature by one for each motor and still be better off .

[jack forsberg]

old school here had a friend with a big motor and a pull cord to start it. I bought a built roto pro company maybe 30 years ago 10 HP ran and started 10 HP and there were two heavier options available. 10 HP could run 3 times that total and you were supposed to start motors in a certain order. I think a smaller one before your 10 HP Max one. Running more motors made the whole thing more efficient as they somehow act as ballasts for each other. Total amperage was less than what you were running no idea how that ballast thing works. Not to go sideways but never see people comparing what is drawn from the different ways of running stuff. Id assume VFD's are cheaper to run as there is no motor to turn over then there is no ballast affect whatever that is and how it works.

Honestly warren Motor's are as dumb as a sack and hammers and you'd be surprised what they can run on . As an example you only need to put power to two it's three hot legs . This is what is feed the idliler . The biggest problems are electronics and efficient but most industrial motors are oversize in horsepower and can take the abuse for many many years . Getting the motors to spin is the easy part ,controlling the machine is a completely different arrangement . The VFD supplies motor control and therefore illuminates the most complicated part of control switch gear . Phase perfect doesn't do this and so if you're running machines off of phase perfect you are relying on a complete sound machine that is not adulterated and in compliance with standard Nema switchgear in regards to thermal overload protection . With vintage Machinery I found this is not a consistent thing . Heaters are usually wrong as well as outlawed contactor blocks being used or being undersized. Especially when converted from 480 to 240

[Alan Lightstone]

I had an interesting conversation with a Felder salesman today. He said that all of the machines I mentioned above are available with identical horsepower 1 phase motors, though they are special order items. Is that possible? Are there 7.5HP 220V 1-phase motors? Wouldn't the current required max out what is available to a residential home? I thought much of the reason to go to higher voltage motors was to half the current required.

[Martin Wasner]

I think that'd be a 60amp circuit.

On 480 that'd be 11 amps, you'd probably put it on a 20amp circuit. Or at least my electrician won't put in anything less than that on 480.

My old widebelt had a 7½hp single phase motor.

[David Kumm]

If you are feeding from single phase, the amperage draw on your meter will be about the same if motors of same hp are single or three phase. If the three phase motor needs 20 amps, you will need close to 40 amps of single phase to convert given losses etc. The three phase motors lack capacitors which eventually fail before the motor, are more efficient, and require smaller wiring and controls. When you get over 5 hp and need 40-60 amp single phase circuits it makes three phase look better. Dave

[Malcolm McLeod]

NEC charts show 7.5 Hp at 230V/1ph uses 40 FLAmps. And the motors are available, but probably not as shelf stock anywhere - - I'd guess they're probably looonng lead time order.

Most electric dryer outlets are rated 50A and assuming a newer home - - where I'd think a 200A panel is typical - - and would support a 7.5 Hp 230V/1ph motor.

Compare to a 7.5Hp 230V/3ph motor at 22 FLA. Wire sizes drop considerably, but only from the device doing your 3ph conversion to the motor. The 1ph side back to the meter will still be carrying 40A with the appropriate wire size (sorry - didn't look that up).

Got curious: Baldor shows up to 15Hp in 230V/1ph/1800rpm motors - - at $5270. Each.:eek:

[jack forsberg]

To calculate the single phase amp draw you simply times the full load amps marked on the three phase motor tag by 1.732 which is the square root of 3

[Alan Lightstone]

NEC charts show 7.5 Hp at 230V/1ph uses 40 FLAmps. And the motors are available, but probably not as shelf stock anywhere - - I'd guess they're probably looonng lead time order.

Most electric dryer outlets are rated 50A and assuming a newer home - - where I'd think a 200A panel is typical - - and would support a 7.5 Hp 230V/1ph motor.

Compare to a 7.5Hp 230V/3ph motor at 22 FLA. Wire sizes drop considerably, but only from the device doing your 3ph conversion to the motor. The 1ph side back to the meter will still be carrying 40A with the appropriate wire size (sorry - didn't look that up).

Got curious: Baldor shows up to 15Hp in 230V/1ph/1800rpm motors - - at $5270. Each.:eek:

Fortunately, Baldor shows the 7.5HP 230V/1ph/3600rpm motors at $1300-$1500. Thankfully 15HP is serious overkill. The 7.5HP/230V/3ph/3600rpm motors are between $1250-$1500, so little to no difference in cost.

Of course, won't be cheap to run wire sufficiently large to carry 230V/40 amps....

Now having to carry 100 amps for a 115 V circuit would be crazy big and expensive. What is that, 2ga or 3ga wire??? The route I won't take.

[Alan Lightstone]

I'm waiting to hear back from the electric company down here as to whether it is possible to get 3-phase power from the utility to the workshop. I should hear back in a few days. If not, it will be either a Phase Perfect, or multiple VFDs, or perhaps just wait until Felder can get me 230V 1phase motors in the needed sizes.

[Martin Wasner]

Now having to carry 100 amps for a 115 V circuit would be crazy big and expensive. What is that, 2ga or 3ga wire??? The route I won't take.

Isn't amperage, amperage? The wire doesn't care about the voltage? Or am I way off base here?

[Alan Lightstone]

Halving the voltage doubles the amperage to get the same power.

P=IxV

[Martin Wasner]

Halving the voltage doubles the amperage to get the same power.

P=IxV

I get that. But isn't the amperage capacity of a given piece of wire the same regardless of voltage? You get more power with 10 amps on 480v than 110, but it's still 10amps?

[Alan Lightstone]

I get that. But isn't the amperage capacity of a given piece of wire the same regardless of voltage? You get more power with 10 amps on 480v than 110, but it's still 10amps?

True, but ordering a 115V 1 phase motor with equivalent HP to the 230V 3-phase requires more current, which then requires larger diameter wire to carry it. I was comparing apples to oranges (115V 1 phase to 230V 3-phase). Not a fair comparison, but it's astounding how much current a 115V 7.5HP motor requires. I really was pointing out the absurdity of that option.

[John Gulick]

VFD's are available in the 6000 HP range (think railroad locomotives,) but you can't afford them. A rotary converter is the best way to go for multiple machines. It's basically a three phase motor, with a method of bring it up to speed. Generated third leg is usually a little lower than other two legs.

+1 We have gone this route for several months and for less than $500 have a great system

[jack forsberg]

True, but ordering a 115V 1 phase motor with equivalent HP to the 230V 3-phase requires more current, which then requires larger diameter wire to carry it. I was comparing apples to oranges (115V 1 phase to 230V 3-phase). Not a fair comparison, but it's astounding how much current a 115V 7.5HP motor requires. I really was pointing out the absurdity of that option.
I understand that you're just going under theory but the fact of the matter is a motor in that configured of winding would never exist . Mostly because of the winding wire size would not fit into the stator core . So generally you'll only find single phase dual voltage Motors up ton3 hp 120/240 i'm not sure what the upper limit is on dual voltage three phase but that's a different type of winding and Motor configuration . 230/460 here in Canada we also have 600 V these are never dual voltage windings . But I have run across six wire star Delta wound 600 volt Motors that were prepared in England for shipment to Canada . Generally European motors arevnot wound the same as the nine lead American style .

[Martin Wasner]

Generally European motors are not wound the same as the nine lead American style .

And I have yet to see a euro motor with a diagram under the doghouse cover explaining what taps to use to switch voltages. It's infuriating. Blowing stuff up is only fun when intentional.

[Darcy Warner]

And I have yet to see a euro motor with a diagram under the doghouse cover explaining what taps to use to switch voltages. It's infuriating. Blowing stuff up is only fun when intentional.
The German stuff usually does, the Italian stuff sucks about that.

[Chris Hachet]

Isn't amperage, amperage? The wire doesn't care about the voltage? Or am I way off base here?Amperage and voltage are inversely proportional. And wire has to have insulation rated for the voltage it carries.

[Alan Lightstone]

So the quote came in from Felder, with a disclaimer that the rep gave the wrong information initially, and only the A941 jointer can come with a 1 phase motor. So, I really do need 3-phase power for these beasts. Either directly from the utility, or via phase conversion of one type or another.

So many useful bits of information from everyone. Awesome responses, guys. Please keep them coming.

[Malcolm McLeod]

Amperage and voltage are inversely proportional. And wire has to have insulation rated for the voltage it carries.

^+1 Or, same idea with slight twist: The conductor size determines the maximum amperage a wire can safely carry; the insulation (thickness & material) determines the maximum voltage a wire can safely carry.

And of course there are eleventy-seven other factors (conduit, wireway, # of conductors, etc.) that are used to adjust the above max value. ....gotta love those codes!

[Malcolm McLeod]

I understand that you're just going under theory but the fact of the matter is a motor in that configured of winding would never exist . Mostly because of the winding wire size would not fit into the stator core . So generally you'll only find single phase dual voltage Motors up ton3 hp 120/240 i'm not sure what the upper limit is on dual voltage three phase but that's a different type of winding and Motor configuration . 230/460 here in Canada we also have 600 V these are never dual voltage windings . But I have run across six wire star Delta wound 600 volt Motors that were prepared in England for shipment to Canada . Generally European motors arevnot wound the same as the nine lead American style .

Not to belabor the point, but Baldor does list a 15hp/230V/1ph motor in their online catalog. No idea if they have ever actually built one:confused:.

[Jeff Ramsey]

Interesting. The VFDs even the 10HP ones on eBay (I will need a 10HP one for a 5HP motor, right?)are much less expensive than I expected.

Are they difficult to program. I'm concerned as the units are Chinese, inexpensive, and may not have awesome English instructions.

I have two Lapond VFDs and their technical support was excellent when I was configuring them.

[Malcolm McLeod]

Interesting. The VFDs even the 10HP ones on eBay (I will need a 10HP one for a 5HP motor, right?)are much less expensive than I expected.

Are they difficult to program. I'm concerned as the units are Chinese, inexpensive, and may not have awesome English instructions.

Alan - The 10Hp Huanyang unit (auction #181949861664, I think?) is rated for an input of 34A (at 220-250V) and for either 1-phase or 3-phase operation. So, each input leg can handle 34A. This would easily carry the 28 FL Amps input needed by a 5Hp motor fed by a 230V/1-phase service (15.5A. output).

It would be a stretch for this VFD to handle a 7.5 Hp motor needing 40 FL amps (1-phase) input, but only 22A out. You'd have to baby it. The input side of the VFD is the limiting factor.

For programming, there are lots of parameters to sort thru, but 90% are probably just fine with the factory preset values.

NOT PROMOTING THIS UNIT - - JUST ANALYZING THE SPECS.

[Alan Lightstone]

Not to belabor the point, but Baldor does list a 15hp/230V/1ph motor in their online catalog. No idea if they have ever actually built one:confused:.
I saw that, but I really have no great desire to install that heavy a motor, and, for whatever reason, Felder doesn't offer 7.5HP 1PH motors on those units.

[David Kumm]

Does anyone have info regarding the Huanyang vfds and if they have improved? Over at the Practical Machinist forum which gets into some pretty detailed and complicated electrics, the Huanyang vfds are prohibited from discussions because the moderators believe them to be so poorly built. No first hand knowledge, just wondering. Dave

[jack forsberg]

Does anyone have info regarding the Huanyang vfds and if they have improved? Over at the Practical Machinist forum which gets into some pretty detailed and complicated electrics, the Huanyang vfds are prohibited from discussions because the moderators believe them to be so poorly built. No first hand knowledge, just wondering. Dave
there position is they are not there support

[jack forsberg]

And I have yet to see a euro motor with a diagram under the doghouse cover explaining what taps to use to switch voltages. It's infuriating. Blowing stuff up is only fun when intentional.
I thinking a diagram would be no help to you:) not every thing can be fixed with a screw driver.:) Dave may like this


https://www.youtube.com/watch?v=vP54mmgv4mM

https://www.youtube.com/watch?v=i4BDBSf9wsU

[Mike Heidrick]

Id post for Huynang vfd support on cnc zone and other diy cnc sites. There are far more cnc machines running chinese vfds than any old ww machines for sure and they are doing darn more sophisticated setups with them. Modbus controls and plc interactions and variable speed ramping models. This is not drive grand dads clausing or aircraft carrier sized jointer to show your poker buddies with only the buttons on the vfd face or maybe a switch lol. They can hate all they want but guarentee those Huynang powered spindles on the cnc machines that are being used are clocking 50x more hours than on the owwm those guys are collecting.

[jack forsberg]

Id post for Huynang vfd support on cnc zone and other diy cnc sites. There are far more cnc machines running chinese vfds than any old ww machines for sure and they are doing darn more sophisticated setups with them. Modbus controls and plc interactions and variable speed ramping models. This is not drive grand dads clausing or aircraft carrier sized jointer to show your poker buddies with only the buttons on the vfd face or maybe a switch lol. They can hate all they want but guarentee those Huynang powered spindles on the cnc machines that are being used are clocking 50x more hours than on the owwm those guys are collecting.
Those drives are garbage even for programming a few bucks more you get some really good stuff . Most modern drives will go up to 600 Hrz and you can buy the spindles from China for dirt cheap . Controls are not so much on the VFD on CNC as they are on the table servos . They all come with plc . A dumb elevator runs on PLC

[Darcy Warner]

Those drives are garbage even for programming a few bucks more you get some really good stuff . Most modern drives will go up to 600 Hrz and you can buy the spindles from China for dirt cheap . Controls are not so much on the VFD on CNC as they are on the table servos . They all come with plc . A dumb elevator runs on PLC

They are cheap and they work great for someone that just needs to run a 3 phase motor from single phase. Installed many of them for customers.

[Malcolm McLeod]

I saw that, but I really have no great desire to install that heavy a motor, and, for whatever reason, Felder doesn't offer 7.5HP 1PH motors on those units.

My apologies, I wasn't advocating the use of 15Hp on your proposed tool stable. I was just curious about someone's comment and looked to see what was largest horsepower motor offered in 230V/1ph.

(I forget sometimes that my schitzo thought processes are not immediately apparent to the outside world. :(:(:(:eek::(:(:( Welcome to the Twilight Zoonnn .... er, SHOP. Yeah. Twilight SHOP.)

[Adam Herman]

I get that. But isn't the amperage capacity of a given piece of wire the same regardless of voltage? You get more power with 10 amps on 480v than 110, but it's still 10amps?

the 480 will burn a hole through the insulation on the 110 rated wire, even if the copper is correctly sized for the current.

[Alan Lightstone]

I haven't gotten an exact quote from the power company, but today they told me that it may be possible to get 3-phase, but it will likely be VERY expensive, so likely a no-go.

BTW, would it matter to the Felder machines if it was 208V 3-phase or 240V 3-phase? It appears that Duke Energy would only provide 208V 3-phase here (if I am reading their information correctly).

[John Lanciani]

the 480 will burn a hole through the insulation on the 110 rated wire, even if the copper is correctly sized for the current.

with the exception of SJ cord which is only rated for 300 volts, virtually all of the wire (THHN/THWN, XHHW, etc.), cord (SO, SOW, SOOE, etc.) and cable (NM-B, AC, MC) used today is rated for 600 volts.

[William Shelley]

I gotta wonder - at what point would it be cheaper to buy a used (or even new) 3-phase natural gas or propane generator and just run that when you are in your shop?

You guys are all laser-focused on treating this as an electrical-only situation when there are other ways to solve it.

[Malcolm McLeod]

I gotta wonder - at what point would it be cheaper to buy a used (or even new) 3-phase natural gas or propane generator and just run that when you are in your shop?

You guys are all laser-focused on treating this as an electrical-only situation when there are other ways to solve it.

...or a water wheel?! :D With the big master shaft run down the ceiling, and the long leather belts on PTOs to the Felders! :cool:

[Alan Lightstone]

I gotta wonder - at what point would it be cheaper to buy a used (or even new) 3-phase natural gas or propane generator and just run that when you are in your shop?

You guys are all laser-focused on treating this as an electrical-only situation when there are other ways to solve it.

That is an utterly fascinating idea, but the neighbors would likely get pretty upset at the noise of the generator. I'm going to very great lengths to prevent noise outside the workshop.

The little stream on the properly could potentially power a 0.01HP motor. On occasion.

[Martin Wasner]

the 480 will burn a hole through the insulation on the 110 rated wire, even if the copper is correctly sized for the current.

But, my original question was is amperage amperage regardless of voltage? Insulation rating is a separate factor.

[Chris Padilla]

with the exception of SJ cord which is only rated for 300 volts, virtually all of the wire (THHN/THWN, XHHW, etc.), cord (SO, SOW, SOOE, etc.) and cable (NM-B, AC, MC) used today is rated for 600 volts. Well, finally something I think I can add to the conversation. So, as has been stated, the size (diameter or more correctly, cross-sectional area since its a volume of metal that the current flows through) of a wire (copper or otherwise) will determine the amount of amperage it can handle before melting or getting too hot to cause other problems. Or as a power company sees it, they want as small a current as possible so they can use as small a wire as possible to save as much money as possible. This is why power lines run in hundreds of thousands of volts and why they use step-down transformers to bring the couple hundred volts into our businesses and homes. As to the insulation on the wire, that is a voltage or more correctly, an electric-field issue. It is known as dielectric breakdown or dielectric strength and is measured in Volts/meter (V/m). There is a particular field strength that a material can handle--usually done on an insulator or a dielectric--before it is no longer an insulator. At the atomic level, the field strength rips normally tightly-bound electrons free from the insulator and it begins to conduct. Once this happens, the insulator is basically destroyed. We all see it burning/melting of the insulator. I'll also note that high voltage power lines are not insulated: costs money and their voltage levels are very high. However, air is also a dielectric/insulator and air also will break down if the field strength is high enough. I think air is around 3 million V/m. I've never heard of a power company running much higher than 800,000 V. But lightning can hit many millions (even billions) of volts so that is why we see it: air is being broken down, electrons ripped from their source, and current flowing--a bolt!

[Chris Padilla]

But, my original question was is amperage amperage regardless of voltage? Insulation rating is a separate factor.

Amperage is the flow of charge. Charge is free electrons that are moving about. In a metal like copper, it has very loosely bound electrons that are easy to break free and move. In fact, most metals exhibit this characteristic.

Resistance is what holds back the flow of charge and takes away energy from the charge moving where it wants to. Resistance can come about from many things but mostly it is energy lost from heat since the electrons bounce around hit things, vibrate, don't travel in straight paths, etc.

From those two, we get voltage: V=iR. Voltage is a convenient form in which to measure and understand and use current and resistance. Current comes from the pure geometry of whatever it is flowing through and resistance as well. One can't talk about voltage without implying current or resistance although we often do. Voltage is easier to use and understand. If one really wants to get to the nitty-gritty of electricity, we should talk in electric (V/m) and magnetic fields (A/m). Current and voltage come about from simplifications of Maxwell's equations but they are still very powerful and easier to use than field theory.

So I hope this helps to answer your question as I'm not sure how to EXACTLY answer your question.

[Alan Lightstone]

Well, finally something I think I can add to the conversation. So, as has been stated, the size (diameter or more correctly, cross-sectional area since its a volume of metal that the current flows through) of a wire (copper or otherwise) will determine the amount of amperage it can handle before melting or getting too hot to cause other problems. Or as a power company sees it, they want as small a current as possible so they can use as small a wire as possible to save as much money as possible. This is why power lines run in hundreds of thousands of volts and why they use step-down transformers to bring the couple hundred volts into our businesses and homes. As to the insulation on the wire, that is a voltage or more correctly, an electric-field issue. It is known as dielectric breakdown or dielectric strength and is measured in Volts/meter (V/m). There is a particular field strength that a material can handle--usually done on an insulator or a dielectric--before it is no longer an insulator. At the atomic level, the field strength rips normally tightly-bound electrons free from the insulator and it begins to conduct. Once this happens, the insulator is basically destroyed. We all see it burning/melting of the insulator. I'll also note that high voltage power lines are not insulated: costs money and their voltage levels are very high. However, air is also a dielectric/insulator and air also will break down if the field strength is high enough. I think air is around 3 million V/m. I've never heard of a power company running much higher than 800,000 V. But lightning can hit many millions (even billions) of volts so that is why we see it: air is being broken down, electrons ripped from their source, and current flowing--a bolt!
6.007???????

[CPeter James]

An interesting thought to add to this thread is that here in New Hampshire, the power company tariffs (rules) on file with the Utilities Commission actually limit the size of electric motors in residential locations to 3 HP. More that that and you are charged at much higher commercial electric rates and a whole new set of rules apply. I would expect that many other locations have similar rules. That being said, I suspect that many of us are in violation of these rules. Fortunately for me, I do not share a transformer with anyone and that probably makes my neighbors happy when my air compressor kicks on or I am out in the shop welding.
C
Peter

[Alan Lightstone]

An interesting thought to add to this thread is that here in New Hampshire, the power company tariffs (rules) on file with the Utilities Commission actually limit the size of electric motors in residential locations to 3 HP. More that that and you are charged at much higher commercial electric rates and a whole new set of rules apply. I would expect that many other locations have similar rules. That being said, I suspect that many of us are in violation of these rules. Fortunately for me, I do not share a transformer with anyone and that probably makes my neighbors happy when my air compressor kicks on or I am out in the shop welding.
C
Peter
I never knew that. Might make for a good reason to not get officially quoted for the cost to bring 3-phase power to the house, just update my 1-phase to add an additional 200 amp service.

[Chris Padilla]

6.007???????

come again?

[Alan Lightstone]

come again?
An MIT Electrical Engineering course that would cover this topic.

I was taking a wild guess as to your Alma Mater, Chris.

Swing and a miss, I guess.