Three Phase to single phase part two

[Michael Handrinos]

​Thank you for all the replies. I should have been a bit more clear with what I want to do. I bought a PW 66TA with a 5 HP three phase motor that I want to convert to single phase. Right now I'm looking to get a convertor instead of changing the motor out. I would have to spend more on a motor than I paid for the saw. I've heard that there will be some power lost but that doesn't concern me being it's 5 HP. The saw is in excellent condition and came with a Powermatic mobile base, 52" rails and a baldor motor. So, would I need to get a new magnetic switch or can the existing one be reused?

Thanks in advance again

Mike

[Kevin Jenness]

The cheapest way out is a static phase converter. You would lose about a third of the motor's potential power. You are still using three phase power, so the magnetic starter remains as is. I have been running my slot mortiser on a static converter for 25 years with no problems.

Variable frequency drives for a 5hp motor can get pricey, but may be the least expensive route if you want full power. With a vfd you can't have a switch between it and the motor, so the magnetic switch is not used.

A rotary phase converter, unlike the other two options, allows you to run more than one machine off its supply. This opens up the ability to buy other three phase machinery in the future, often a relative bargain because so much of the hobbyist market is in the same boat as you are now. Again, the magnetic switch is still used.

As an example of a cheap RPC setup, I found a used 10hp motorfor $175, hooked it up to a $200 control box full of capacitors from WNY Supply, and a used distribution subpanel that cost me about $125 online. I run a 6.5hp slider and a 5hp planer off this setup, with room to hook up further machines. I nearly bought a used commercial 10hp rpc with subpanel for $900, just to give you an idea of what's available on the used market.

[Doug Walls]

​ Right now I'm looking to get a converter instead of changing the motor out.

I built my own 3-phase converter from designs I got from the internet, It's not really that hard to do if your familiar with 220-volt wiring & basic electronics.
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My set-up is a 5HP RPC that runs on a 30AMP 220-Volt circuit & will run 3HP & under 3 phase motors.

To run your 5HP 3 phase motor you would want to use a 7-1/2HP or more RPC & probably would need a 40-amp 220 volt supply line.

Doug

[Doug Walls]

​ The saw is in excellent condition and came with a Powermatic mobile base, 52" rails and a baldor motor. So, would I need to get a new magnetic switch or can the existing one be reused?
If you go with a static phase or RPC unit you should be able to use the same mag. switch.

Doug

[Mike Heidrick]

$200 will buy you a 4kw 5hp vfd off ebay. No power/hp loss. No free spinning idler motor noise. Programmable start and stop timings.

I use both rpcs and vfds so i am not biased.

[Bruce Page]

This guy has been powering my 2hp milling machine and my 5hp engine lathe since the mid 90's without a single hiccup.
If I were setting up today I'd go with a VFD.

[Bill Dufour]

If you use a VFD you can use the original push button switches but bypass the contactor they control.
Bill

[Rollie Meyers]

When a static phase converter, it starts a 3Ø motor but the motor is then being single phased, not really a good condition.

[Allan Speers]

Mike, FWIW, a VFD also offers the advantage of speed control, and dynamic braking. (better VFD's brake better, though you can sometimes add resistors to cheaper VFD's) This is a very nice thing to have on a table saw.

Also, don't buy a super-cheap import VFD on Ebay. They are legendary for being garbage. The minimum price for an "acceptable" 5 hp unit will probably be around $350. Stick with TECO, Hitachi, Yaskawa, etc.

[Chris Hachet]

This guy has been powering my 2hp milling machine and my 5hp engine lathe since the mid 90's without a single hiccup.
If I were setting up today I'd go with a VFD.


I have had very good luck with VFD for phase conversion.

[Chris Hachet]

Mike, FWIW, a VFD also offers the advantage of speed control, and dynamic braking. (better VFD's brake better, though you can sometimes add resistors to cheaper VFD's) This is a very nice thing to have on a table saw.

Also, don't buy a super-cheap import VFD on Ebay. They are legendary for being garbage. The minimum price for an "acceptable" 5 hp unit will probably be around $350. Stick with TECO, Hitachi, Yaskawa, etc.Quoted for truth-I Love the soft start the VFD gives my Unisaw.

[William Shelley]

A better title for this thread is "Single phase to 3 phase". You're trying to get a 3-phase tool running using single-phase power.