Rotary Phase Converter Rebuild / Build

[Eddyde]

What is it mounted to?

Mounted ours to top of post for car lift and very loud due to shapes of post.

Recounted with isolators and problem solved.

Sent from my SAMSUNG-SM-G930A using Tapatalk

Thanks,

It has soft rubber isolator feet and is sitting on a concrete floor, looks like Mr. Snyder knew vibration would be an issue...

 

[JimDawson]

Thanks Jim, I remember following that thread. As always, you did an awesome job. I guess I'm ultimately heading down that road too, in pursuit of RPC harmony...

Thank you for the kind words

Ha, it sure does looks like Mr Snyder was a little light on the engineering...
Originally, I was going to build the RPC from scratch, I was hunting around for a 10hp motor when this complete one crossed my path for $200. I figured it was ready to go and would save time and hassle, fool that I am...
So now I've been reading lots of articles and schematics on RPC design, trying to figure my next move. I would like to reuse the idler but don't know its horsepower rating so Im not sure how to calculate the cap values?
I'll probably go with a version of Jim's design, though perhaps not as fancy..

From the looks of the motor it doesn't look like it could be over 5 HP, just judging from the size. I would start there for caps, then add or subtract as needed. The fact that it seems to have no start relay makes me wonder if is some kind of purpose built idler just for an RPC. I have heard that with a special winding configuration you can spin one up without a start circuit.

 

[Karl_T]

Yep, not having start caps that drop out after a few seconds is surely the problem here. The system I built for my son vibrates terribly until the start caps drop.

 

[markba633csi]

ED: first thing I would try would be to put a switch in series with the cap bank and throw it open when the idler is up to speed. See if the vibration/hum is reduced or even eliminated. Obviously there will be a voltage imbalance with the caps out of the circuit, but this test would give you an idea of how smooth the system could potentially be, with some circuit changes...take care not to get shocked
mark

 

[Eddyde]

From the looks of the motor it doesn't look like it could be over 5 HP, just judging from the size. I would start there for caps, then add or subtract as needed. The fact that it seems to have no start relay makes me wonder if is some kind of purpose built idler just for an RPC. I have heard that with a special winding configuration you can spin one up without a start circuit.

Yes it appears to be a dedicated idler as no shaft is protruding at either end. Thanks, I'll start at 5 hp and see how it goes...

ED: first thing I would try would be to put a switch in series with the cap bank and throw it open when the idler is up to speed. See if the vibration/hum is reduced or even eliminated. Obviously there will be a voltage imbalance with the caps out of the circuit, but this test would give you an idea of how smooth the system could potentially be, with some circuit changes...take care not to get shocked
mark

Thanks, I'll give that a try. I'm also going to change the bearings on the idler, years of vibration must have beat em up pretty bad...

 

[Eddyde]

Yep, not having start caps that drop out after a few seconds is surely the problem here. The system I built for my son vibrates terribly until the start caps drop.

Thanks, I'm definitely going to add a start circuit relay.

 

[markba633csi]

You could just have a momentary pushbutton to start, save a few $

 

[Eddyde]

You could just have a momentary pushbutton to start, save a few $

I may, depends on what I find in my "miscellaneous electrical" bins.

 

[Eddyde]

So here's where I'm at, I ordered a bunch of run caps, enough to give me 5 to 200 µF X 2, a 270-324 µF start cap & 15k Ω 2W resistor. I have a momentary start-stop switch and I think I have a 3 phase magnetic motor starter (just have to find it) I also have a time delay relay I could use for the start circuit.
I have most of the design more or less figured out.
One grey area I'm still trying to understand is how to figure the power factor correction cap values?

 

[JimDawson]

One grey area I'm still trying to understand is how to figure the power factor correction cap values?

The way I did it is to put the amprobe on the incoming line and start switching in caps until I ran out of caps to switch in. Every cap I switched in lowered the incoming amps. I have 25 MF connected.