I have a problem that i have lost three pumps in the last two months. I have not been able to pin point the exact cause. I have installed a new pump two days ago it worked well for two days and now has now stopped working new contactor and over load was installed. Found the blue phase on the contactor contacts was burnt in side of the contactor. found the power factor to be reactive on two of the phases of the motor and the other inductive. what can be the fault if some one can help with info please.

 

Please provide detail, such as:

1) Hp, Volts, speed, starter-type, size, type, & length of downhole feeder!

2) What setup are you using to measure "powerfactor?" Are you using a
3-phase Watt/Var meter? Or are you monitoring individual phases?

3) What are service parameters?

4) Is system solidly grounded/earthed? Or, ungrounded/unearthed?

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}

 

1. Check for lower supply voltages occuring at peak hours.
2. Install a thermal overload with single phasing preventor.
3. Replace or check the no-load trip system if it is a deep borewell, this should cut off the pump when the flow go to minimum.
4. Are you using repaired (rewound) motors then try replacing with new set.
5. Is the water pumped out is clean? Check if muddy or dirty well water is not loading the motor.
6. Is the pump oversized to the motor capacity? Control your pump outlet flow for some days to keep the motor current to be witin limits.
7. Dismantle one motor and check the following,
If only one or two windings burn out then it is the single phasing problem. If the supply voltage at the stater outgoing is normal then the cable fromm the starter to motor might be a problem. If there is sign of sparking in the windings the insulation might be a problem particularly on a rewound motor. Do not rewind a motor more than few times as the motors do not work well after a few burn outs.
8. It is unlikely that a motor will have different power factors in three phases. Probably the way you measured need to be looked into.

Regards,
Sekar

 

Hello there

I assume that you have a 3 phase cable running down the bore hole and connected to the motor cable with a Scothcast or Raychem jointing kit. These joints have been known to fail, especially if they are in deep water. If that happens, water will get into the cable and into the motor windings and cause a short circuit.
Water will also travel up the cable (along the copper strands) to the level of the water surface. This has happened to me. If you don't know this is happening and you just put down a new pump with the old cable. Then the water in the cable will run down into the new pump and blow it up as well.
It is easy to see if your cable has water in it. The copper strands will be damp and slightly blackened.
If so, there is nothing you can do except replace it.

Regards
Jamie Downs
[email protected]