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racear*2865
09-05-2009, 10:01 AM
To Any One That can Lend assistance
I have a 15hp rotary converter that I constructed and I am attempting to hook it to a 7.5 Delta variable frequency drive. As I apply power to he vfd, it will immediately fault from the wild leg. If I measure the individuals legs to ground. They read T1--118, T2--120volts andT3--185. T3 is the developed wild leg. When the VFD sees that leg it faults. I do not know how to get around this. I tried adding run capacitors, but it raised the T3 voltage even higher. Can any one lend me some knowledge
thanks
racear

Al_The_Man
09-05-2009, 10:05 AM
It is probably sensing the high voltage, try reducing the run capacitor value, this should drop the 3rd leg down.
Al.

racear*2865
09-05-2009, 01:38 PM
Al
I do not have any run capacitors in the circuit. I have already removed them. That is why I dont understand this thing
racear

Al_The_Man
09-05-2009, 02:18 PM
Thats unusually high without any caps, are you using a 2 pole motor (~3500 rpm) for the RPC.?
Al.

racear*2865
09-05-2009, 06:45 PM
Al
No it is a 1750 rpm

bocko912
09-09-2009, 01:15 AM
I just finished a 10hp RPC and balanced it within 3%. I am using it on a 5HP cnc with a V1000 Yaskawa VFD. My voltage to ground on T3 is 216 volts and T1 is 118 T2 is 120. More important is your balance you must have run caps from T1 to T3 and T2 to T3. I ended up with 80MFD on T1 to T3 and 44.5 MFD from T2 to T3. This gave me a reading of 250 to 251 volts from T1 to T3 and T2 to T3. My single phase in is 244 volts across T1 and T2. My Idler is a 240/480 volt 3ph Delta 1750 RPM from an old air compressor. It balanced perfectly. I don't think your drive is faulting from a high leg because true 3phase 240 delta has a wild leg that is 240 volts to ground and 2 legs that are 120 volts to ground. Let me know if this helps

John

deanq
09-11-2009, 12:18 PM
bocko912 is correct. Balance your RPC phase-phase, not phase-ground.

racear*2865
09-13-2009, 11:03 AM
Fellows
thanks for your inputs.
will reconnect the run capacitors and re balance. Is it possible that the VFD is seeing the imbalance and faulting
racear

bocko912
09-13-2009, 03:12 PM
Does the drive fault just booting up the machine or does it fault when you try to run the spindle?
John

racear*2865
09-14-2009, 10:50 PM
Thanks
It faults when I boot up the VFD
racear

racear*2865
09-16-2009, 10:37 AM
I have balanced the 3 legs to within 3% underload but it continues to fault
racear

bocko912
09-16-2009, 01:05 PM
You should balance the RPC with no load first then after its balanced under no load take voltage and amperage readings apply your load and then take readings again. Your voltage readings should decrease and amperage readings should increase evenly across your phases. Is your VFD new or used?

racear*2865
09-16-2009, 01:48 PM
Ok I can do that. The unit is used as I had it on a lathe earlier. It is a Delta VFD-B series
racear

racear*2865
09-16-2009, 01:51 PM
also after I balanced under load. I started another machine and everything was ok. It did not fault and ran great. Figure that
racear