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tommy2630
05-12-2011, 09:59 PM
Hi,
Does anyone have any experience running a 10hp cnc router (plus 10hp vac pump) using a 3 phase converter?
If so, can you suggest a good UK manufacturer of rotary converters.
Thanks,
Tom

m_c
06-12-2011, 06:28 PM
I don't have experience of running motors that big, but you're looking at 30A current at 240v under full load for each motor, and start up current is going to be far higher, which you'll really struggle with using any normal single phase supply.

Jonathan
06-12-2011, 07:44 PM
Why not use a VFD? Obviously expensive for that size, but the starting current is much much less as you can set the acceleration to a long time. Still as m_c said 10hp/7.46kW is a lot for a normal supply, but will you actually be running the motors at full load?

m_c
07-12-2011, 12:24 AM
The other issue is the motors might not be able to run on 240V, so you'd also have to factor in a step-up transformer. Even if the motors are capable of running on 240V, then you'll still need to change the control gear.

In short, it's going to be expensive.

Jonathan
07-12-2011, 12:55 PM
The other issue is the motors might not be able to run on 240V, so you'd also have to factor in a step-up transformer.

If the coils can't be swapped round in the motor then if it is acceptable to have a fraction of the rated power then it can still be run on 240V.

Jon S
07-12-2011, 01:19 PM
If the coils can't be swapped round in the motor then if it is acceptable to have a fraction of the rated power then it can still be run on 240V.

True but you would want to know how the current increases as the voltage drops and the net effect on the temperature, so not a safe assumption.

I use a much smaller TransWave which I have been very happy with the tech support for, so would recommend you talk to them for a baseline of what would solve your requirement.

Jonathan
07-12-2011, 01:30 PM
True but you would want to know how the current increases as the voltage drops and the net effect on the temperature, so not a safe assumption.

Yes, hence de-rating the power. Would need to work it out properly first of course...

Jon S
07-12-2011, 01:52 PM
I am somewhat baffled about where this idea of running the motors at a lower voltage has come from, my rotary converter on 240v single phase gives 415v on 3 phases.

Jonathan
07-12-2011, 02:21 PM
I am somewhat baffled about where this idea of running the motors at a lower voltage has come from

A VFD run from a 240V supply just rectifies the input, so unless it includes a voltage doubler on the input (don't know if that's something that's available, wouldn't be surprised) it cannot run the motor on 415v.

This article explains about the various ways:
http://reviews.ebay.co.uk/3-THREE-PHASE-CONVERTERS-INVERTERS-415V-DIGITAL-ROTARY?ugid=10000000001476333

Jon S
07-12-2011, 03:07 PM
Well clearly from the ebay article you cite Rotary phase converters are a thing of the past.

Edit - Sarcasm is so easy :-) The chap is clearly considering his options and they are problematic in any direction, I am sure he is aware of that and not planning to install in his attic !

Cheers,

Jon