# 600V 3-phase motor (milling machine) --> 240V operation



## slow-poke (Apr 20, 2017)

I have been on the lookout for a bench top mill for occasional use (should be a good compliment to my Emco 8 lathe). I found a local one for a reasonable price ($500) however it is powered by a 3 phase 600V motor. So I would either need a converter or replace the motor to single phase 240V.

Has anyone done this?

Converter or swap the motor?

Estimate $ for the conversion?


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## markba633csi (Apr 20, 2017)

You could shop around for 600 volt variable frequency drives and compare the price vs a single phase motor- The VFD would give you some speed control but at what cost?
Mark S.


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## CluelessNewB (Apr 20, 2017)

Unless it is some weird frame size motor I would suspect finding a replacement single phase motor would be the least expensive option.  

I don't know of any 240V single phase input VFD's that output 600V 3 phase.   

You could build a rotary phase converter to convert from 240V single phase to 240V 3 phase and then add a 3 phase step up transformer to get it up to 600V.  I don't think that would be very cost effective for just one machine.


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## hman (Apr 20, 2017)

slow-poke said:


> I have been on the lookout for a bench top mill for occasional use (should be a good compliment to my Emco 8 lathe). I found a local one for a reasonable price ($500) however it is powered by a 3 phase 600V motor. So I would either need a converter or replace the motor to single phase 240V.


A *benchtop* mill with that huge a motor???  Sounds like the seller or a previous owner went *way* overboard on power!  And I can almost envision a huge motor scabbed onto a small mill and overbalancing it to the rear 

I'd agree with changing out the motor for a single phase 240V (1 ½ to 2 HP) as the most economical solution.  Round column mills (which I'll suppose your candidate is) come from the factory with such motors.  Often they're wired for 120/240, but the current draw at 120V is pretty high.  So 240 is the way to go.  You'd have to rewire the switch, of course.


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## CluelessNewB (Apr 20, 2017)

hman said:


> A *benchtop* mill with that huge a motor???



Just because it is 600V doesn't mean it is all that powerful.   It might be only 1hp.


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## slow-poke (Apr 20, 2017)

I spoke with the seller, he will send me a picture of the motor plate, he said he does recall it being 1.5HP


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## tq60 (Apr 21, 2017)

Do not waste time here.

The 600 volts may be wrong data as this looks like typical hf or other low end mill.

Get photo of actual motor to confirm as it is likely single phase native voltage of where first sold.

If it is some odd 3 phase voltage the cost to convert to single phase house voltage more than mill is worth.

If price is real cheap the motor can be replaced as they just mount to plate at real like normal drill press which these mills are almost...

Sent from my SAMSUNG-SGH-I337Z using Tapatalk


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## 4GSR (Apr 21, 2017)

In the Canadian area that he's in, it is very likely the motor is set up running off of 575 volts, not 600 volts.  That is a common voltage for that area.  I have a surface grinder that had a 575 volt motor on it that can from that area.  Guess what, it got pulled and chunked into the junk pile, and a 230 volt 3 phase motor put in its place. I operate it off of a VFD on 230 volt 1-phase now.  Ken


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## Chipper5783 (Apr 21, 2017)

Sure.  Not really a big deal (been there done that).  I assume that you have 3 phase power (RPC, or what ever).  When faced with the same issue, I got a 240-600V 3 phase transformer (found a good used one), plugged it into my 3 phase (RPC) distribution and it works great.  I now have 3 machines on this (having 600v - 3 phase has opened up some nice opportunities).

I was fortunate to get the transformer for $100.  However, powering things up was just so easy (no issues with motor mounts, shaft size, controls) - the changes are external to the machine.  Of course it is possible to change motors - depending on all sorts of factors whether it is easy or hard.  All I am presenting is that plugging in a transformer is easy.

If I were to do it again and I had to pay $1000 for the transformer - I would still go with the transformer option (quick, easy, works great - sometimes those considerations are worth paying for).

Let us know how you make out.  Regards, David


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## Keith Foor (Apr 24, 2017)

Be advised about running equipment above 440 volts.  
For some reason the 400 volt threshold is a level not to be crossed by the faint of heart.
240 volts if it shorts will typically just make a bang, melt some wires and blow a breaker.
The higher voltage stuff will create sustainable arc's and plasma balls that will burn for a longer period of time and tend to really roach things before it gets done cooking.

I am not trying to indicate that it's not safe.  It's used every day in industry and works well.  But it has to be respected more than the low voltage stuff for the reason mentioned above.
Be safe and have fun


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## slow-poke (Apr 25, 2017)

Thanks for the advice. 

Yes 600V definitely needs to be treated with respect, I recall from an electrical safety course (many years ago), that this is the most common voltage responsible for serious accidents and fatalities.

I have a few pictures of the motor.


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## slow-poke (May 11, 2017)

Making progress........

Managed to get the mill home in my wife's mini-van, disassembled it into three pieces. Loading was easy, four "He-man" at the pick up location man handled it into the van , and then I pulled it up and out the side door with a chain lift. Then built a rolling base to get it to its new home location. I'm not sure how much it weighs but must be in the ballpark of 450-500lbs.  I have a used 1.5HP, "Inverter Duty" 240V, 3-phase motor with the same frame size as the original on order.  I also picked up a used but supposedly good Altivar 31 VFD which is now wired (less the motor side).

I would like to perform a preliminary function test of the VFD, test: forward, reverse, speed etc. If I were to try powering the original 600V motor (no load) with the 240V, VFD do you think it will spin with the reduced voltage?


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## 4GSR (May 11, 2017)

slow-poke said:


> Making progress........I would like to perform a preliminary function test of the VFD, test: forward, reverse, speed etc. If I were to try powering the original 600V motor (no load) with the 240V, VFD do you think it will spin with the reduced voltage?


Nope!  Got to have the same voltage from the VFD to the motor.  You more than likely will fry the VFD trying.  Ken


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## British Steel (May 11, 2017)

I've tested VFDs without frying them by  putting three lots of 240V bulbs across the motor terminals, keep adding bulbs for more load...

Hard to tell whether it's in forward or reverse, or what the speed is though 

Dave H. (the other one)


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## hman (May 11, 2017)

British Steel said:


> Hard to tell ... what the speed is though


2.99793E10 cm/sec


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## Chipper5783 (May 11, 2017)

slow-poke said:


> I would like to perform a preliminary function test of the VFD, test: forward, reverse, speed etc. If I were to try powering the original 600V motor (*no load*) with the 240V, VFD do you think it will spin with the reduced voltage?



It won't hurt the motor.  It is very common for service shops to* no-load *test motors at reduced voltage (talking good sized motors - such as a 13.8kV run at 4160V).  I understand in the motor world, 600V is still considered low voltage - so they wouldn't test that at a reduced voltage, but only because 600V is readily available.  I also don't think it would hurt the VFD - the full load current draw of a 1.5 HP - 600V motor is probably less than 2 amps (with the actual motor winding sized accordingly) - it will not suddenly draw big current (beyond the typically expected inrush).  Can you program a current limit into the VFD?  No-load means remove the v-belt.

If you were going the other way, with a 240V motor and running on 600V through the VFD (expecting the VFD to protect itself and the motor)?  That would be ill advised!

Let us know how you make out.  David


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## slow-poke (May 12, 2017)

I paralleled the 2nd and 3rd phase on the input of the VFD and connected it to 240V,  and then hooked it up to the original 600V motor for a reality test. Unloaded it works just fine, forward, reverse and from very slow to > 1800RPM.

VFD was a great suggestion, thanks to all.

Can't wait to get my 240V motor, it might arrive today.


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