I have an 8 year old 15 HP 600V ventilation motor(E-Line EM122) that has blown a fuse twice over the last six months. The first was on C phase and the second was on A phase. Both times the breaker tripped as well. It runs without a problem once the fuse is replaced. The motor is downstream from a disconnect which is downstream from the magnetic starter. Breaker > starter > disconnect > motor.
The fuses, breaker and overloads are all appropriately sized. While under load the motor pulls about 6A on each phase and about 575V at the disconnect. The connections are good and so is bonding continuity between the disconnect, connection box, and various parts of the motor frame. The leads don't have any noticeable damage on the insulation.
I megged the motor leads at the connection box as well as at the disconnect(to check the wires between the disconnect and motor). The megger(TES 1601) has a range of up to 4G Ohm at 1000V and all of the tests read OL. I thought this was strange so I tested the megger on another motor(100M Ohm) as well as doing a continuity check with the leads and everything looks good. The first time I tested it the motor was cold so I let it run overnight and retested it this morning with the same results.
I am out of ideas on why this keeps happening.
The fuses, breaker and overloads are all appropriately sized. While under load the motor pulls about 6A on each phase and about 575V at the disconnect. The connections are good and so is bonding continuity between the disconnect, connection box, and various parts of the motor frame. The leads don't have any noticeable damage on the insulation.
I megged the motor leads at the connection box as well as at the disconnect(to check the wires between the disconnect and motor). The megger(TES 1601) has a range of up to 4G Ohm at 1000V and all of the tests read OL. I thought this was strange so I tested the megger on another motor(100M Ohm) as well as doing a continuity check with the leads and everything looks good. The first time I tested it the motor was cold so I let it run overnight and retested it this morning with the same results.
I am out of ideas on why this keeps happening.
