That's a big motor for a rotary phase converter. You might
have better luck using a smaller pony motor to start it up.

Ignoramus18851 wrote:
There are some intermittent problems at home related to me starting my
RPC. It is beginning to affect my marriagee.
....
I suspect that it is so because the main 10 HP motor takes a
comparatively long time (1-2 seconds) to spin up, and draws about 120
amps during this time.

Ignoramus18851 wrote:

On Thu, 12 Jan 2006 14:19:49 -0600, Mike Berger wrote:
That's a big motor for a rotary phase converter. You might
have better luck using a smaller pony motor to start it up.

Thanks Mike, that's a good point and one I may have to consider.

i

Ignoramus18851 wrote:
There are some intermittent problems at home related to me starting my
RPC. It is beginning to affect my marriagee.
...
I suspect that it is so because the main 10 HP motor takes a
comparatively long time (1-2 seconds) to spin up, and draws about 120
amps during this time.

--

Do you spin the smaller idler up first? If not it would likely help
start the larger one.

Pete C.

Ignoramus18851 wrote:
On Thu, 12 Jan 2006 14:19:49 -0600, Mike Berger wrote:

That's a big motor for a rotary phase converter. You might
have better luck using a smaller pony motor to start it up.


Thanks Mike, that's a good point and one I may have to consider.
There are easier ways. One way is to rig a time delay relay, and
start the converter on 120 V, then when it has spun up, have a
double-throw relay (got to be break before make) switch it to 240.
This will drastically reduce starting current. it will also take a
little longer to start. If the simple way is too massive an unbalanced
load on the breaker panel, then you could use a step-down transformer
or autotransformer to make 120 V from the 240, and draw it balanced from
both hot wires.

It is possible some motors won't rotate at half voltage. If so, you
can use the traditional scheme of capacitors that makes the idler motor
start faster on the normal voltage. It should allow the idler to start
up at the reduced voltage.

It is fairly common on larger motors to use a Delta-Wye starting scheme
to reduce the starting demand. The motor is connected in the WYE
configuration to start, then when up to speed, the wiring is changed
over by a relay to the delta configuration. (This of course requires
a motor where both ends of each winding are brought out.)

Jon