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

[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.

[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.

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.