Rotary Phase converter problem

John_Dennis

John_Dennis

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My Rotary Phase converter is putting out high voltage on 1 leg. I suspect that the capacitors are shot, can anyone provide any wisdom on this?

Ground to 1 123 V
Ground to 2 123 V
Ground to 3 225 V

1+2 246 V
1+3 265 V
2+3 246 V
 
I removed the two capacitors, Anderson MFG was unkind and removed the Capacitor labels. The capacitors are round aluminum run capacitors 2 1/2 inches x 4 7/8 and the horsepower on the nameplate is 7.5

The two capacitors were wired parallel in between 1 leg of the 220 and the 3rd leg output + 3rd leg motor input

Can anyone give me an estimate on the amount of capacitance needed and the type of Capacitor I should purchase?
benmychree said:
Does it make your 3 phase motors start and run well, if so, no problem.
Click to expand...
what happens when you double the voltage on 1 leg of a 3 phase motor?
 
That's not bad for a non electronic balanced RPC. Wild legs can be even higher but generally the legs balance better under load. The ideal voltage on the manufactured leg would be 208 to ground but I've seen numbers higher than yours . Dave
 
Beckerkumm said:
That's not bad for a non electronic balanced RPC. Wild legs can be even higher but generally the legs balance better under load. The ideal voltage on the manufactured leg would be 208 to ground but I've seen numbers higher than yours . Dave
Click to expand...
265 while running a 1 hp bridgeport seems high enough to damage the motor. thats a little over 50 volts too high.
 
Are your measurements while running with a load on the BP? That does seem out of balance. Whether it hurts the motor depends on the insulation. I worry more about undervoltage as that increases the amp draw and causes the motor to run hot. If the motor is 200 or 208v that is pretty high. If the motor is 220-240, not so much.

RPC balance differently under different loads so a large rpc doesn't balance well under light load. My rpc that would start a 10 hp motor, didn't balance well on small motors but was fine at 3 hp above. I now run a phase perfect and it balances from 30 hp to 0. Dave
 
There are some great threads here by @Ulma Doctor where he walks thru making your own phase converter and he gives capacitor sizes based on HP.

If you cannot find them, let me know.

Brian
 
The measurements to ground are not meaningful. Only be concerned with the phase to phase readings; some variation is ok
-M
 
Are those phase to phase readings while the rpc is under load? If those are unloaded values, they may change to a more acceptable value while running a machine.
 
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