Rotary phase converter versus trying to run a VMC straight from single phase

I friggin give up....

WHY, WHY, WHY do you need a pony motor for a 20 horsepower idler????

A few thousand Mfd worth of starter caps, and it will SNAP to full RPM in a Fraction of a second.. WHY make it so extra complicated?

Hi Half

Dont give up so quickly. You can learn about this stuff if you take just a little time to think about it.

Some people just like the use of pony motors. They dont consider them so extra complicated.

Some people have difficulty getting their capacitor switches to live due to contact arcing.

Some guys even blow up capacitors due to inappropriate On time.

Sometimes capacitors are not reliable.

Spinning up rotary converters is kind of a presonal preferance thing. I use capacitors and a solid state switch for my 3 phase motor spin up.

Jerry

It's NOT true. I originally had my 20hp converter hooked up to a 60amp breaker. Never had a problem.

I changed to a 100amp breaker when I hooked up the second converter. Both converters, the 20hp *and* a 15hp, running off the same 100amp breaker. Both converters ran daily, for 4 years. Never even saw the lights flicker.

Matt

Ok. That's all good news that I've seen from the group regarding breakers not popping. I'm looking for run caps and start caps now to get this thing going.

Thanks!

You can always contact Reed @ Convert-A-Phase.

He's here in Escondido. I bought a 20hp box from him. Start caps, run caps, all set up and ready to go. Bought a used 100apm disconnect from him, and hooked up my own 20hp motor. Even got him to come over to the house and tune it for me.=20

IIRC, the control box was just under $500, and maybe another $100 for the disconnect. But that was 11 years ago.

It might be cheaper to build it from scratch, but the peace of mind in knowing that you have all the right caps, and everything is connected properly, and all you have to do is run your 220v to the box, is worth every penny you'll spend on that control box, IMO.

Also bought the 15hp box from Reed and added my own disconnect and motor. I mounted both of them on wooden frames and hooked them up to breaker boxes, and had breakers for each machine. The 20hp ran 4 cam operated Swiss screw machines, a CNC Gang Tool lathe, a tool grinder, a bridgeport, and an engine lathe. The 15hp only ran a Tornos 5-axis CNC Swiss. You'll notice voltages increasing and decreasing as machines are turned on & off. I didn't want to take any chances with the Tornos.

Warning! DON'T mount them on wooden frames! At least don't mount the motor on wood. I made the base out of 4x4's, with a double thickness of 3/4 plywood and bolted the motor to it. Big mistake! Those things make a constant humm anyway, but the wood was the prefect acoustic base it needed, and it amplified the hummmmmmm. Drove me nuts!=20

Matt

Terry,

Enough that I was actually quite surprised, but not my job to provide finer details so suggest you should look it up yourself....IIRC only 5 % and things start into getting "iffy"...

Anyways, my specific app is heat pump compressors ( a situation where a burnt-out motor isnt easily replacable by itself )

The project has been delayed for other reasons but it involves shop heat using 4 each 2-1/2 ton well water sourced heat pump units at 460-3... which I will derive from a 230 v rotary phase converter and then step up a via delta/ wye connected transformer...suffice it to say I *will* be adding a handfull of capacitors so as to more evenly balance the voltage / phase when these actually do come on line.

Ad-nauseum...

You obviously had motor rated breakers.

Gunner

Yes. Mine was slightly more clever than this.

1) I used two contactors instead of 3. Which worked well, they just needed to be wired differently. 2) The first motor had a capacitor on legs 1-3. It assisted with starting, but resulted in unbalanced 3 phase. 3) The second motor had a capacitor between legs 2-3. When it was connected to the network, the capacitors became equal between legs 1-3 and 2-3. That resulted in a much more balanced 3 phase. i

Hi Matt,

That made me laugh. I mounted one of our home made cap-style 10hp rotary converters on rubber and it made it's hummmmm about 10 times louder too. It is back on the concrete and barely audible again.

Dave

Really!? How about that. I would have thought the rubber would help. I may wind up back in the garage. Still have the converters and was planning on making a heavy steel frame, with rubber feet, or put it on felt pads.=20

A friend has a 10hp that is mounted on two pieces of steel channel. The control box is attached to the rail/motor, and it just sits on the floor. The disconnect and breaker panel are mounted to the wall. It's really quiet.

I kind of liked having it all together in one unit. Makes it easy to move around when needed. Perhaps I should reconsider.

But then, I've also thought....... If I have to do it again (move back to the garage), the converters may wind up out in the shed:-)

Matt

The hummmm noise is mostly due to field imbalances in the converter. In other words, they are an electric problem. My old converter was making a lot of hummm, but on my new one, all noise is from bearings, fans etc and is all high frequency. No hummm. That's because it is electrically balanced.

i