Single Phase Pump Motor Winding Burned

What kind of protection do you already have in place for the pump? Ok so you don't have overload, but what about Dry run protection? Pressure(based on your application)? thermo-coupling for mechnical stress of bearing? thermistor for over heat protection? if your pump is submersible do you have protection against humidity?

ELCB, absolutely nothing; for dry run we have provided float switch this is booster pump. I strongly believe should go for a stater with OP relay for this operation.How do you feel?

What's an OP relay?

First you need to check if your pump features Overload protection and/or over heat protection (I've seen a few pumps that feature internal overload protection but not over heat), if you are missing any of these two then you need to apply them externally. Overload is a just a relay above your starting contactor, for over heat use a thermistor relay.

The third you will need is the thermo coupling for your mechanical bearing to flag any mechanical friction.

Hopefully you understand these measures will only stop your system before any damage takes place and give a better understanding of when and what the cause of the problem is likely to be. It is not a means to make your pump function with out disruptions.

Thanks for the info.

What is the rating of the generator ? How did you determine "no variation in voltage" ?

You are operating a 3 HP pump it seems ? Does your motor selection include thermal protection ?

50/60 hertz being considered ?

You really haven't given enough information for us to help you.

if you have no motor protection then you are now experiencing the result of either not knowing you need motor protection or knowing but not installing because of costs.

You can do as much damage to the motor during underload as you can during and overload situation. Both can burn out the motor.

Find a good pump supplier and ask about motor controller, that has both overload and underload protection. Once installed you should not have this problem again.... unless you haven't told us everything.

I had to go away and read about underloaded motor protection.

Underloading can happen if the cooling fan stops pumping air (or other) while the motor is rotating. Restricted airflow or a disintegrated fan or running dry...

This won't detect failure if the motor is loaded though....

Under Load Protection: It may seem surprising to talk about under load protection when motor protection is normally required when overloads occur. In cases where the motor is cooled by the medium it drives, such as fans and submersible pump motors, a lack of this medium (due to an obstruction of air or liquid flow) would result simultaneously in a reduced motor load and excessive motor heating. For this reason a warning signal or a trip before damage occurs is useful.

Underload.. a condition that occurs when the motor is NOT working normally or NOT loaded.

In my industry which is ESP's we DO NOT run without underload protection, as it is the fluid passing OVER the outside of the motor that is the cooling medium as the ESP motor unlike a surface motor has no fan or cooling fins to dissipate the stator heat.

As for motor failure.. any underload system/motor controller/relay is not designed to detect a failure, just an underload, overload, over & under volts etc, condition.

The underload condition is a percentage of the running current. I use 80% of running current with a time delay of about 1 to 2 mins before tripping, to allow for gas that has formed in the pump, which does give you an "underload" condition.

Gas is just the tip of the iceberg, there are many, many conditions that cause underload.

Cool.