RPC Theory Question

[Shanghyd]

I have a machine that requires 440V 3 phase. I want to test the machine out before I change the motor to a 220V 3 phase motor. I don't have the funds for a lot of conversion stuff at this point.
So I'm thinking...I have 2 each 7.5hp 220V 3 phase motors sitting around not doing anything.
If I wire one as an RPC to 220V and then couple the two motor shafts together, but wire the second motor up as a 440V motor, will I get 440V out?
The 2nd motor will be output only. Will it work as a generator? I can wire the 2nd motor that's putting out 440V to the machine that requires 440V and see how it runs.
What do you all think?
Is there a better way to get 440V 3 phase from 220 single phase?

[Geof]

No your motor wired 440 will not act as a generator.

You need a rotary phase convertor using one of the 220 motor as the idler and then a 220 to 440 3 phase transformer.

[Al_The_Man]

First check out why it needs 440?
Is it just one motor that requires it? Can you change the motor to 220?
Even spindle controllers are often dropped down to 220v 3 phase.
The control itself most likely does not need 440, maybe 120?
It is worth looking into a bit deeper, unless you already have?
Al.

[Shanghyd]

There are two motors on the machine. They both have 440V tags. There isn't a 220/440 option. There are 3 wires going to / coming from the larger motor. The smaller 440V motor is used for picking off or deburring. Its a CVA No. 8 screw machine from England. Looks similar to a Brown and Sharpe.

http://s724.photobucket.com/albums/w...37;208%20Auto/

[IMG][/IMG]

[mactec54]

Just change the motors out & you will be running

[Al_The_Man]

If they are an odd ball shaft/mount size, you could look into getting them rewound for 220v.
Also, check into the present termination, as to whether they are connected in star?
You may be able to connect in delta for 220v.
Al.

[Shanghyd]

I got a quote for rewinding. $250 which isn't bad. Too bad its not in the budget right now.
There is a motor start block of sorts and it has 230V on it. I'll post a pic when my camera batteries are charged up.
I hooked my VFD directly to the motor and it spun. I was able to control the rpms of the motor through the VFD. I could control it just like my lathe 3 phase motor.
So if this is indeed a 440V motor am I going to hurt anything by running it at 220V through this VFD?

[scotta99fan]

I owned the exact same model CVA as you show in your picture. You should keep in mind that the CVA No8 was equipped with motors that were wired for50 cycles, not 60. The motor will run faster than the nameplate states.

Scott