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220 V 1Ph to 600 V 3Ph Help Needed

metronorth

Hot Rolled
Joined
Jun 30, 2004
Location
Brampton Ontario Canada
I have read many threads from this and other sites and I have gained some knowledge but not enough to feel confident about investing in hardware yet. I received (for free) a large lathe that requires 600v 3Ph. I have 100 amps of 220 going to my garage. I believe I need to purchase a rotary phase converter and a transformer to create 3Ph then step it up to the required voltage. The machine manual recommends 30 amp feed. There are 3 motors in the machine, an 11Kw spindle motor, a lube pump motor and a rapid feed motor. There is also a small transformer that creates control voltages. Changing to a lower voltage would not be a reasonable proposition. I am making the following assumptions;

30 amp x 600v = 18KVA so I believe a 20 KVA 220 - 600 transformer is required.
18KVA x 1.5 = 27 KVA so I believe I need a 36 hp phase converter.
36 x 750 = 27000 watts or 123 amps so I believe my amperage may be limited but this seems excessive to me based on the actual current draw of machines I have owned in the past.

Another way to look at this is total machine Hp (17) requires 23 amps at 600V or 14KVA. Could I use a 15KVA transformer and a 25hp phase converter which I could feed with 85 amps?

And then of course there is inrush current, isolation vs auto transformer, step up vs back feeding a step down transformer and many other unknowns. Any pointers would be greatly appreciated.

Glenn
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
you can feed a 20hp with about 85A
I have done this all, auto transformer and a 20hp spindle to drive a 10HP cnc mill that says 63A at 230V
biggest thing is having a big enough rpc to drive it, without it the voltages spike all over.
also check the voltages now and again, here in canada it goes up and down like crazy off the 240V.
 
Last edited:

bob

Titanium
Joined
Aug 12, 2002
Location
Regina, Canada
Common problem for us in Canada. I run a 10 hp Phase Perfect to generate three phase feed a 30 kva transformer wired backward to boost to 600 all on a 40 amp breaker this will run a 10hp 600 volt motor motor but it is marginal. The limiting factor seems to be the phase converter.
Bob
 

beckerkumm

Hot Rolled
Joined
Aug 5, 2014
Location
Wisconsin Rapids WI
My experience ( not expertise ) tells me the 100 amp input is marginal at best. There will be losses along the way and starting up a large old machine takes some reserve. If you are also running lights, air, etc on the 100 amps you don't have all of it available. The transformers are also generally oversized a little more than your example. You might make it work but I'd oversize the rpc and transformer so if you have problems it is only the wiring that needs to be swapped. Keep in mind that some rpc will be sized by the largest motor they will start and others by how much hp they can handle. An Am rotary 25 hp won't be adequate ( 30-40 would ) but a 25 hp Kay would. Both would want more than 85 input amps.

I'd also prefer an isolation step up transformer but will let others guide you there. You could also consider a motor swap. I just bought a NOS Marathon Black Max 10 hp 230v three phase motor ( $2500 new ) for $350 including shipping. Motor deals are out there and even with new starters might cost less than a transformer and eliminate the input amp problem. Dave
 

metronorth

Hot Rolled
Joined
Jun 30, 2004
Location
Brampton Ontario Canada
Thanks gentlemen. I just stumbled on an RPC and transformer pkg on Kijiji that is being used to start and run a 15hp motor at 600v. I will take a look at it tomorrow and see what supply amperage is being used. I find that things nominally run at far less amperage than the max rated startup peaks and the motor in the lathe has a current limiting start circuit on it. The lathe is in my garage and there will be no other loads other than lighting and it’s all LED. I will reply again after I see the RPC.
Glenn.
 

motion guru

Diamond
Joined
Dec 8, 2003
Location
Yacolt, WA
Make sure you have disconnect switches or contactors between your phase converter and your transformer - starting the phase converter with the transformer connected creates a very high current draw at startup. Best to start the phase converter all by itself, then connect the transformer, then start the lathe.
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
Thanks gentlemen. I just stumbled on an RPC and transformer pkg on Kijiji that is being used to start and run a 15hp motor at 600v. I will take a look at it tomorrow and see what supply amperage is being used. I find that things nominally run at far less amperage than the max rated startup peaks and the motor in the lathe has a current limiting start circuit on it. The lathe is in my garage and there will be no other loads other than lighting and it’s all LED. I will reply again after I see the RPC.
Glenn.
That the ADX american rotary on there im guessing?
 








 
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