Rotary Phase Converter

[jeremy13]

Ok I got the plastic injection machine in place. And was looking at the electrical. I thought I had it made. The machine has a 15HP hydraulic pump. And I have a 25HP 3PH motor laying around. So I was going to make a rotary phase converter for it. But looking at the other guys rotary's for sale. They suggest a 40HP rotary for my machine. That is one big motor. So I was thinking if I put some 3PH capacitors in the out put legs of the rotary. Will that help kick start the 15HP pump? Or just bite the bullet and add another 15HP idler motor.

[Carld]

What does your injection machine run on? 220v or 440v? If my memory serves me the injection mold machines pulled a lot of amps and I remember the motors sounded like they were under a load at times but that was a long time ago.

I think your going to see a lot of surge current with the injection mold machine. I would guess you may need a 40 or 50 hp RPC. Others may have a better idea of the load you will see.

You WILL have to balance the legs for it to run right.

[SGW]

Understand that I have no actual experience with rotary phase converters...

...but what I've read about them suggests an RPC motor 1.5X to 2X the size of the motor you're going to run. If that guideline holds true in your case, you should be okay. It may depend on how much of a starting load is on the machine's motor.

Try it and see what happens!

[Iraiam]

Go to Arco Electric, my favorite brand of phase converter. they have a sizing assistance web page that is quite handy, not only is the motor HP important but also full load amps. and voltage.

40 HP RPC does not seem out of line for a machine with a 15 HP hydraulic system on it, as a hydraulic system would be a different kind of load than some others, say an air compressor for instance.

http://www.arco-electric.com/Sizing.aspx

[Don Young]

Try the 25HP motor. If not satisfactory change to a larger motor for the converter or just add another motor. 'Balancing' capacitors can increase the converter's capacity and reduce the line current, but are not necessary.

[jeremy13]

My machine was factory shipped as a 240V unit. And converted at the buyers factory 480V. By rewiring the motor and adding a 480 to 240 transformer to run the controls. Best I can tell the heaters in the magnetic motor starter are still for 240V. And the fuse for the band heaters are still the same amperage. I will try the 25HP motor and just leave room in my capacitor box for more caps if the 25 doesn't work.

Iraiam- ARCO suggests an HD15 if I just factor in the motor. But if I add in the band heaters in the FLA category it go's to a HD30. I don't know if this is a 30HP motor or not.

[fredf]

Iraiam- ARCO suggests an HD15 if I just factor in the motor. But if I add in the band heaters in the FLA category it go's to a HD30. I don't know if this is a 30HP motor or not.

Just a dumb thought, can you rewire the heaters for single phase 240??? they sure don't inherently NEED 3 phase

[jeremy13]

Fredf- I'm with you I don't know how you wire in 3Ph ( 3 hot wires ) and the band heaters only have 2 wires. I guess you drop a leg of power and don't use it. In that case I just have to make sure that the heaters are connected to the non-generated legs.

[chipmaker4130]

When you hear 1.5 - 2 X tool hp for the rotary, they're talking about low-load startup. If you're going to run a large compressor or if your hydraulic pump starts under load, it will probably need to be higher. Also, keep in mind that the source circuit must be capable of supplying (at least for start-up time) max current for the tool PLUS max current for the generator. Also, on a high-load system you don't want to run the load side L1, L2 thru the generator start contactor. It should go direct from source to tool start control. Only L3 should come off the generator system.

[Carld]

jeremy13, you need a wiring diagram for your machine.

I don't think the heating coils are three phase but I guess there are three coils and each coil is on one leg of the three phase to balance the load.

With the heaters, feed motor on the screw and the hydraulic pump I think your going to see some high spike current loads. You can try the RPC you have but I doubt it will pull the load.