hot running motor 10

[steveholloway]

i have recently connected a star delta motor. it starts up and runs fine but it it is running quite hot. when i checked the current reading for each phase i found the following; red was 3.5A yellow was 4A and blue was 4.5A
i felt that this was not normal ie they should all be the same the motor is a grundfos lpo80-125-133 at 4kw pumping 80 tonnes per min can any one help me
Cheers steve

 

[aolalde]

Steve Hollogan.

The current unbalance is creating a small magnetic field but running backwards. That field reduces (brake) the effective shaft torque and it is producing heat, which is a reason for the increased temperature rise.

Current unbalance could only be the result of non symmetrical windings or unbalanced voltages. The reported currents average 4 amps and a maximum unbalance of 0.5/4*100= 12.5%. However, to produce this current unbalance only around 1.5% of voltage unbalance is required, say 374.7, 380, 385.7 volts. See STD NEMA MG1 part 14.

If the unbalance can not be corrected, this motor load should be reduced not to exceed 3.9 kW. This could be achieved reducing the overload current setup.

 

[steveholloway]

thank you for that information i have yet to get back to the motor the people are on holiday but when i do i will check the voltages and the temperature with a heat probe thanks again

steve