Phase convertors?

[Kurt Wyberanec]

Hi all, as some of you know and a boat that many of you are probably in, in looking at a new saw and wondering if a phase convertor is worth it for me.

Most of you have suggested phase perfect, a digital static convertor vs a rotary model for a number of reasons and with even the little bit I know about them it makes sense to me.

Of course this does bring into account a substantial cost even if used (though I haven't seen much used) so there is a trade of but it opens other possibilities. In my case I might also have to revamp my electric because it might be a bit undersized but going to look into that.

My question is aside from phase perfect are there any others you might recommend? Searching a bit I found the place below that sells digital static models at a ridiculously low price and I can't understand the price disparity... they mention if you need different hp than what it listed to just contact them. The largest they list is only 3hp and I probably want 7.5-10 but their 3hp is only $89!!! That's only about 25x less than a 7.5 pp.... what gives? I know a lot of people say you get what you pay for and generally that's usually true but definitely not always the case and it leaves me thinking but this is a huge price gap.... maybe I'm missing something and maybe there his hidden cost...I might call for a 10hp unit they might say 3k who knows.

So long story short, take a look at this let me know what you think and let me know there are any other good quality lower cost alternatives to pp...I don't think I want to go rotary because it will increase my bill significantly and almost definitely increase a lot to the install since I will definitely have to upgrade the panel.

Am going to put a call into pp for additional info.

Thanks in advance!

[Charles Coolidge]

What 3 phase machines do you plan to run?

[Andrew Hughes]

I have a Kay phase master. It’s so quite I leave running more then I should. As far as cost running or idling it doesn’t draw anything worth mentioning idling. Running it’s just a third 120 v leg.
What I learned from installing a 3ph system. Installing a bigger panel with more circuits doesn’t necessarily mean my service is upgraded.
How close I am to the transformer and the size of the line drop wire play a part.
Good Luck

[Jared Sankovich]

The phase perfect isn't a static converter. The $89 version (and they all basically) are just a start capacitor. The motor only runs on 2 phases as the static converter just allows it to start.

A phase perfect is closer to a vfd but without the drawbacks (other than price)

For a single saw a $250 vfd makes more sense than a rpc or a PP

[Mark e Kessler]

A PP is a digital converter not a static converter which is not what you are looking for. Did you not go the PP website, they have tons of info A new 10pp is probably around 4k, metal working forums are a good place for used ones. For rotary go to American rotary’s website they have tons of information. Probably around $1500 for a 20hp which will run 10hp. Ypu can probably get a used Rotary for $500 or under and you can also make them yourself.

Jared makes a good point, I didn’t even think of a VFD for a single solution could be good but if you are planning for the long ter a PP or rotary makes more sense but could be a way to just start with the saw for low money

[Kurt Wyberanec]

Hi Mark, I've looked at the site and learned quite a bit... when looking at this cheap o product i just saw I didn't realize there was a difference since they call it a digital static convertor... the pp just says digital convertor guess I didn't realize there is something different going on and being this stuff is pretty new to me I'm trying to learn the differences.

[Kurt Wyberanec]

What 3 phase machines do you plan to run?

Mentioned looking at a new saw.. slider... outside of that no current plans though have a line on a seemingly great deal on a wide belt but would only be buying it because of the deal and possible future (not current) needs... biggest downside would be where to put it so it's not in the way lol.

[Kurt Wyberanec]

The phase perfect isn't a static converter. The $89 version (and they all basically) are just a start capacitor. The motor only runs on 2 phases as the static converter just allows it to start.

A phase perfect is closer to a vfd but without the drawbacks (other than price)

For a single saw a $250 vfd makes more sense than a rpc or a PP

Oh boy, now something new to consider! The price point is definitely more attractive... what can you tell me? Brands to look at? Size needed? Etc. This would be for a slider probably 5- 7.5hp plus scoring motor. Thanks!

[Phillip Mitchell]

Seems like there may be some fundamental misunderstandings in your original post. Not sure if I have the time to speak to all of them and there are more knowledge folks on here that can speak to 3 phase conversion as well.

Here are some things you will want to think about directly and assess. Giving answers in this thread will help folks give accurate recommendations and answers because it’s a bit of shooting in the dark without details.

How big of a motor (s) are you planning to run with a phase converter? Ideally the answer would be in amps but HP ratings will get you close.

What are the details of your current electrical service? Ie: how many amps is your current single phase 240v panel? Are we assuming that you are a 1 person shop and will only be using 1 machine with a dust collector simultaneously? What size motor on the DC?

You can essentially figure on feeding twice the amount of 220V single phase amps into a phase converter than what you will get on the output 3 phase side. Example - I have a Kay Phasemaster rotary phase converter that will start up to a 10 hp 3 phase motor. I have 4 gauge wire coming from a 60 amp breaker in my single phase 240v panel going into the phase converter which can produce ~30 amps 3 phase at 240V. A 10 hp 3 phase motor could be rated at ~25-30 amps at 240V so hence the capacity to start and run that size motor.

A Phase Perfect compared to a cheap static phase converter is complete apples to
oranges and not at all a like comparison. Phase perfect is a high quality digital converter that produces a totally balanced voltage output across all 3 lines and is designed to accommodate electronically sensitive equipment / motors (think CNC, highly automated saws/shapers/etc with a lot of electronics on them)

A simple static phase converter like your talking about for $85 is something that can start a 3 PH motor (often at a reduced / limited capacity) but it not set up to run it continuously on proper 3 phase power. A rotary phase converter is designed to start and run 3 phase machines continuously on relatively balanced voltages for extended periods of time and typically does so with the use of an idler motor that helps generate the 3rd leg of the 3 phase. Some of them are more balanced than others across all 3 lines. My Kay typically has 2 lines at whatever my incoming utility voltage is (248v last time I checked) and 3rd “wild” leg at around 275V. This isn’t really a problem with simple machines and motors but may not be the best choice for more sensitive motors / controls like CNCs, etc. I have simple machines and motors and it works great for me.

With the Phase Perfect product, you’re paying for a few things - simplicity of setup, extremely balanced voltages for use with sensitive motors, and a relatively compact and well engineered package / system that often times doesn’t need anything else.

Rotary phase converters can be similarly equipped and be just as effective.

I have ~$1500 or less into my system that will start a 10 hp motor that includes a 3 phase MLO subpanel with separate breakers and receptacles and a transformer so I can keep all my 3 PH machines plugged in at once and run multiple motors simultaneously (shaper with power feeder for example)

You can also do the same thing with a VFD though that would be for only 1 motor and typically the VFD does not want any machine controls/switches in between the motor and the VFD wiring so it then becomes your controller for turning the motor on and off. Large VFDs (over 5 HP) can get expensive, though still probably cheaper overall for just one big one compared to a RPC or Phase Perfect setup.

I do not notice additional electrical expense from running my RPC and it’s attached idler motor, FYI.

I don’t know if I answered everything but hopefully this helps?

edit: I see Jared and mark jumped in while I was typing my novel, but hopefully this helps your understand the differences and more of what you need.

If your potential saw has separate main and scoring blade motors (many do) then you will likely need a separate VFD / control for each, though scoring motors are small and VFD will be pretty cheap for that.

[Malcolm McLeod]

Oh boy, now something new to consider! The price point is definitely more attractive... what can you tell me? Brands to look at? Size needed? Etc. This would be for a slider probably 5- 7.5hp plus scoring motor. Thanks!

A VFD on a slider would be possible, but lots of work to implement. You could easily run both the main motor and scorer on a separate VFD, but it is not a matter of installing a VFD ahead of the 'saw' and the VFD delivers 3-phase power to the saw. You cannot have a relay (the typical OEM, as-supplied, electro-mechanical starter) in the line between the VFD and the motor.

Then if you install a VFD, you have to determine how to interface to it: start / stop / speed. You basically have to gut the OEM electrical system of the saw and rebuild it around the VFD(s). Doable, but make sure you know what you're getting into.

[Bruce Wrenn]

Oh boy, now something new to consider! The price point is definitely more attractive... what can you tell me? Brands to look at? Size needed? Etc. This would be for a slider probably 5- 7.5hp plus scoring motor. Thanks!

Look at some of the machinest web sites. They have TONS of info on phase converters, include shop builds. The most expensive part of a shop build, isn't the motor, but the wiring and controls associated with it. Used 3 phase motors can be purchase at salvage yards for less then $0.25 per pound. Most 3 phase motors were removed from service due to bearing failure. Ten bucks worth of bearings, and you are good to go for a lifetime. About twenty years ago, I built a rotary converter for my neighbor, using a three phase motor and a "pony motor" to start it running. The pony motor can be replaced with capacitors and a start switch. Throw the power switch on, and push the button. If power fails, magnet relay kicks out to protect motor from frying due to lack of rotation.

[Jared Sankovich]

A VFD on a slider would be possible, but lots of work to implement. You could easily run both the main motor and scorer on a separate VFD, but it is not a matter of installing a VFD ahead of the 'saw' and the VFD delivers 3-phase power to the saw. You cannot have a relay (the typical OEM, as-supplied, electro-mechanical starter) in the line between the VFD and the motor.

Then if you install a VFD, you have to determine how to interface to it: start / stop / speed. You basically have to gut the OEM electrical system of the saw and rebuild it around the VFD(s). Doable, but make sure you know what you're getting into.

Didn't realize when I originally posted it was a multi motor slider. 2 vfds and the control wiring would make all the other options easier. Not to mention the price for a 7.5-10hp vfd would be $650 then another $200 for the scoring saw vfd.

[Malcolm McLeod]

Didn't realize when I originally posted it was a multi motor slider. ...

I've been following Mr. Wyberanec's other thread on sliding saws, so I made the leap that "saw" was a slider... .

[Charles Coolidge]

I opted for a rotary phase converter from American Rotary, the only phase converted approved by HAAS to run their CNC machines.

[Bradley Gray]

I'm currently running a Kay rotary 10 hp rated to start 10 hp and run 20. I got a deal I couldn't refuse on it about 5 years ago.

Before that I used a homemade RPC with 7 hp idler started with capacitors.

I have 13 3 phase machines connected.

The simplest system I've seen was a machinist friend - a 10hp 3 phase motor with a flat belt pulley that Ron spun up to speed with his foot every morning.