Help with Rotary Phase Converter

[Lasernerd]

Ok
I have a 20hp RPC complete with starting circuit and balancing bank/
I have 3 legs and a ground Black,White,Red and ofcourse Green
question is the Black and White go to the house mains 240V
and the Red leg is the generated 3rd leg is this correct

 

[BB]

I am not quite sure what you have for a RPC--is it a motor/gen set, or simply a three phase motor being use as a rotory converter itself... If it is the second, here is one short article about setting it up (seems to be an OK article):

Phase Converter

Years ago, I had setup a friend's machine shop in his garage doing this... At the time, it was recommend that the three phase motor/converter was a "Y" or "WYE" wound (as opposed to a DELTA wound--"triangle" as I don't have a DELTA key on my computer) and ran at ~3,450 RPM (instead of the 1,725 RPM or so motors that are also available).

Operated several machines (Bridgeport Mills, 5 HP turret lath from WWII, and even an CNC lathe)... I made sure that the controller/electronics were all wired to run off of the 240 VAC mains, and that the generated phase was only running the motors.

I have not tried using the caps as a starting circuit for the three phase "converter" listed in the above link--neat solution if it works well.... We simply used a small motor and belt to get the big 5 HP converter spinning at a good clip and threw the switch--the converter quickly came up to speed and we never had on bit of problem (other than dimming the neighbor's lights with initial testing of turning everything on and off quite a few times in the first hour--and converted an air compressor used to run a CNC Bridgeport to continous run to reduce the starting loads--Once the converter was started--there were no apparent issues).

There are warnings from others that these types of converters are not recommended as they can cause equipment to overheat and fail because the third leg is not true 3 phase power factor corrected power...

As always--this is dangerous stuff and if you don't know what you are doing--don't do it.

-Bill

 

[Lasernerd]

Thank you,
My unit is factory built
I am more than sure the Red leg is the generated one,my unit is self starting
and the 3rd leg is balanced,my unit is a 20hp unit

 

[Pellidon]

We have shipped some of these with the machines we make. The rule for the rotary ones was the load had to be inductive and not solid state. The last time we used a solid state converter. I don't recall it having any restrictions on the load.

Balance was the key. We also had a single phase transformer to get 110 in the machine. I had to be careful to make sure it was not across the "fake" leg.

I see them advertised all the time in the back of wood working magazines.

 

[Lasernerd]

We have shipped some of these with the machines we make. The rule for the rotary ones was the load had to be inductive and not solid state. The last time we used a solid state converter. I don't recall it having any restrictions on the load.

Balance was the key. We also had a single phase transformer to get 110 in the machine. I had to be careful to make sure it was not across the "fake" leg.

I see them advertised all the time in the back of wood working magazines.

Yep that is correct,
My next question is where to get a 3 phase buck-boost transformer to take the 240V down to 208V.before or after motor
This is used to power large frame ION lasers

 

[benh]

My understanding is that 208 is 240.

That is, 208 is the nominal input voltage rating. Much like 110 VAC nominal is really 120 VAC. So, unless your equipment has *really* tight tolerances on input voltage, you're probably ok.