On Feb 12, 1:56 pm, "Jerry" wrote:
"Brent" wrote in message

...



On Feb 12, 11:20 am, "Jerry" wrote:
"Nick Mueller" wrote in message

...

Jerry wrote:

A 3 phase motor will supply nearly full power
when running on single phase, but it will stall much more easily than
when
it has 3 phase power.

I see a slight contradiction in this statement.

If all 3 of your 4 KW motors are spinning at the same time from the
same
power connection, you will have made your own 3 phase power within the
unit's wiring anyway.

And you only have to feed in 1/3 of the wattage.
Quick, quick! To the patent-office! :-)

Nick
--
The lowcost-DRO:
http://www.yadro.de

Hi Nick

I recognize that you are a smart guy, so there is a misunderstanding.
I say that a 3 phase motor can deliver nearly its full name plate rated
power to the load when it is running from a single phase power source. I
suspect that you agree.
I say that a 3 phase motor will stall more easily when running from a
single phase power source than when running from a 3 phase power source.
You certainly agree with that.

I considered that when one of the three motors is spinning, it becomes
a
"rotary converter" for the other motors. My thought was (is) when the
system of 3 motors are included in one machine, not all will be loaded
simultaneously. That assumption could easily be an error.

I am open to learn. Where is my thinking wrong?

Jerry

Jerry

the unloaded RPC motor acts as an LC network and creates the needed
phase shift.

the RPC motor is not being used as it was originally intended as a
LOAD its being used to pass power through it and apply a phase shift
rather than to transform the power into mechanical energy.

The rpc will not generate the third leg properly until it is spinning
at speed. once it is spinning at speed it will take a tiny amount of
power to keep it spinning at speed but that will be insignificant
compared to the load

the 3 motors in the machine are running as loads and are taking power
out of the system rather than generating extra power on the third leg.
and should be treated as loads that remove power

Hi Brent

It isnt clear that the OP is considering a Rotary phase converter. A
converter is often a capacitor that is temporarily connected to the 'not
connected leg' of the 3 phase motor. Once the 3 phase motor is spinning, it
will run well with single phase input power while the third leg of the motor
disconnected.

3 phase motors run well when fed single phase, once they have "spun up" to
near their synchronous speed. A 3 phase motor running from single phase
will delliver very nearly its name plate reted power to a load.

Once one 3 phase motor is spinning, any additional motors connected in
parallel with them will see the "spun up" motor as its being a Rotary phase
converter with single phase power applied to their input.

Bob Swinney wrote a good article describing most of the theoritical
aspects of Rotary Converters.

Jerry

My brother is planing to use one of these of suitable size.
http://www.grizzly.com/products/Stat...-to-7-HP/G5843
Thanks everyone.
Karl