He says it popping the 50A breaker. Code for rpc's allows for over sizing wires for max amp draw.I (tentatively) think that if it's not popping the breaker, going to a larger one isn't going to increase the current flow. It's not a hose, it's a switch...
Hopefully one of our electrical guys can help here, but would you confirm that when the machine is in gear (with motor off) the spindle turns relatively easily, i.e. no apparent binding, just normal load from all the rotating elements?
Using your reference terminology for my 5 Hp RPC:California, definitely 60hz.
Just got off the phone with the phase converter company and they recommended boosting the generated leg with extra capacitors. They said 100-200 uF per line. Anyone have an opinion on that? Seems easy enough and inexpensive. The current run capacitors are:
L1 -> L3 (generated): 150 uF
L2 -> L3: 50 uF
Thanks this is really helpful. It puts me in the pocket of what the phase converter company suggested. I'll be adding 100uF to each leg so it'll be 150uF and 250uF. I guess I'll just keep an eye on the voltages.Using your reference terminology for my 5 Hp RPC:
L1 -> L3 : 50 uF (C13)
L2 -> L3 : 90 uF (C23)
The ratio of C13 to C23 is 0.55. The same ratio works for me at 2 Hp.
Might be correct for a 10 Hp unit. I worked this out with lathe running at the rpm range most often used.
I would try:
C13 = 180 uF
C23 = 100 uF
The capacitor designations I use have the values reversed from you. That means the direction of rotation is reversed.
I keep everything turning clockwise when looking at the shaft end. I assume your are using oil filled capacitors, the ones
with aluminum cans. I bought my caps at Grainger.
Ok, I guess I didn't fully understand that post. Are you saying:After over 20 years mucking with RPC stuff I would not depend on any run capacitors to fix your issue.
If you cannot get the lathe motor to run freely as a RPC idler then the motor has winding short(s) that weaken the magnetic fields inside.
The only fix is another motor. See post #10.
Yes, but you have to determine if the motor swap with no other changes made to the RPC will be ok.Ok, I guess I didn't fully understand that post. Are you saying:
disconnect the 10hp rpc idler motor from the rpc box
connect the 5hp lathe motor (without belts) to the rpc box
run the rpc, and see that the 5hp motor starts quickly like the 10hp does. If it starts slowly then the new 5hp motor is bad
**Do I have to worry about higher line current exceeding the 5HP motor's FLA from the RPC capacitors? Or maybe just a quick on/off isn't much of an issue...
Am I understanding this correctly? You ran an extra 10 gauge wire (singular) for the generated leg? Or 2 extra 10 gauge wires for both legs of the single phase power feeding the RPC?Yesterday I ran an extra 10gauge wire across the shop and spliced it into the breaker and RPC, just to see if larger gauge would help. It would be like having one 6 AWG wire instead of my 8, and there was no change to the voltage drop at startup on that generated leg.
Thanks for the reply - It's a good point about the WEG. I replaced it with a TEFC cast aluminum instead of the original ODP (whatever Japanese motor was in there since the 70s). The motor frame size now is a 4 Kw where it used to be 3.7, so a little bigger. Also a good point about running another idler. I was also reading about folks putting a large sheave on their rpc idler to keep the rotational inertia.Adding capacitors might do something, in general it does not fix startup issues. Can fix running voltage issues. Startup is a heavy load, and larger capacitors are also a load..... And, the startup load fouls up the effect that capacitors can provide (the heavy load lowers the "Q" of the circuit)