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Transformer help

Transformer help

Transformer help

Hello guys,

I have 2006 CNC 3 axis Bridgeport/Harndinge EZ Vision Mill

My machine is wired for 3 phase 460 volts

2.0 KW
3.3 amps and 1.1 Spindle amps

My question,

I only have single phase 240 coming in the shop.

I also have a used Hitachi VFD. http://www.clrwtr.com/PDF/Hitachi/Hitachi-NE-S1-Drives.pdf

What kind of transformer do you guys recommend to boost the volts from 240 to 460? Installed before or after transformer?

RE: Transformer help

First, for a utilization voltage of 460 Volts, the supply voltage is 480 Volts.
This makes the selection of a transformer easier.
The web site that you list does not show a 480 Volt version of your VFD.
For one motor, you could install a transformer between the VFD and the motor. This would need to be either three transformers in an auto-transformer wye configuration or two transformers in an open delta auto-transformer configuration.
However, your machine draws 3.3 Amps yet only 1.1 Amps goes to the spindle.
That suggests more than one motor.
From the information given you may not be able to drive this machine with only one VFD and a transformer.
Consider a rotary phase convertor.

"Why not the best?"
Jimmy Carter

RE: Transformer help

You need to convert the mill to 240V. This is usually pretty straight forward. You change some taps in the motor or control cabinet(if they brought all the wires from the motor into the cabinet) and you change where some wires land on the control transformer.

Once you have it properly wired for 240V get a VERY modest rotary phase converter (RFC) that you run with your single phase. The rotary converter consists of a strange motor with no external shafts sticking out of it and a control panel.

If you have 240V single phase just hook up the rotary phase converter via an appropriate circuit breaker. Out of the rotary converter use a small 3-phase panel with a breaker or two to distribute the 3-phase coming out of the phase converter.

I suggest you call these guys:
and ask what model they recommend.
If you google RFCs you will find a truck-load of suppliers. In the last two weeks I've been called out three times for shops using RFCs to run large CNC machining centers and they all used American Rotary and thought highly of them and their service.

Before you do that stop and consider any other 3-phase things you might add to your flock and make sure the RFC is sized accordingly so you don't have to do it all over again.

Also remember that the current demand will double when you drop from the totally inappropriate 460V down to reasonable 240V when taking to the RFC people.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Transformer help

Great advice Keith. I see that these units may be paralleled to increase capacity when more equipment is added.
If ore three phase equipment is anticipated in the near future it makes sense to size the RPC accordingly. That would be cheaper than adding another phase convertor in parallel.
If new equipment is a long term maybe, then it may be better to wait until it happens and then make a decision on a second unit in parallel or a second stand-alone unit.

"Why not the best?"
Jimmy Carter

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