Re: [CAD_CAM_EDM_DRO] Phase converter question

A static converter is little more than a motor start capacitor. A fancy
static converter has a start capacitor, a run capacitor and a current
sensing switch that drops the start capacitor out as the motor comes up to
speed.
If you add a three phase motor to the above, you have a rotary phase
converter.
Three phase motors are easy to find and if you are building your own
converter, size it to about 10% over the size of the largest load you need
to start.
I have a 5 hp converter and for a test I had three Bridgeports and their
spindle motors (2 hp each) running and then I started my 5 hp lathe. When I
reversed the lathe at full RPM, it tripped the circuit breaker. The circuit
breaker is only 30 amp so I am not surprised that it tripped. This is a home
built converter.
Darrell

----- Original Message -----
From: Drew Rogge <drew@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Wednesday, July 05, 2000 1:47 PM
Subject: [CAD_CAM_EDM_DRO] Phase converter question


> Well, I'm about ready to build a static phase converter to test an old
> 3/4 hp 3 phase motor I got with a lathe and am planning on using the
> design at:
>
> http://web.wt.net/~hmsc/phconv/phconv.htm
>
> But since I know very little about regular old A/C electricity, as opposed
> to the digital kind, I was wondering if someone could be a bit more
> specific about the type of dual primary transformer that is being used to
> derive the AC neutral in the second diagram. I don't want to sound like
> too much of a bozo when I walk into my electronics store to buy one. I
guess
> the only real question is how many amps the thing needs to handle. Could
> someone explain what this transformer is really doing? Layman's terms
would
> be helpfull here. Are inputs 1 and 2 on the 120 volt side and inputs 3 and
> 4 on the 220 volt side?
>
> Also, will this converter be able to run the motor in reverse? How about
> immediatly reversing the motor? Is it ok to switch the motor on the 3
phase
> side of the converter or should the switch be on the input side?
>
> Thanks for all the help and wish me luck,
> Drew
>
> --
> Drew Rogge
> drew@...
>
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