Part Wind Start overload sizing?

[Morgan3]

What is the proper way to size overload protection for 3 phase Part Winding Start motors? The is a contactor and adjustable overload device for the start and run windings.

 

[Jraef]

Are you sure it's Part Winding and not 2 speed? Usually there is only one OLR on a PW starter.

 

[Morgan3]

Part Wind Start

Part Wind Start

Yes, this is a pump application they have typically used overload protection devices on the start and run windings. The way I understand it once the motor is started each windings carry 1/2 of the FLA of the motor.

 

[wchild1520]

Two contactors , two "OL's" , two sets of windings , each set carries half the load. Set the "OL's" accordingly.

 

[wchild1520]

Look at NEC 430 section III .

 

[Morgan3]

Fuse sizing for the Part Wind motor

Fuse sizing for the Part Wind motor

Typically the Pump Panels are 75 to 200 HP. When sizing the fuse protection for the panel we take the FLA of the motor and mulitiply it by 175% for time delay fuses. Since this motor starts at a lower current should I be able to use a factor 0f 150 % times the FLA of the motor.Since it is a part wind motor.I am trying to stay in a smaller disconnect if possible. I also do not want to cause a problem later down the road with blowing fuses because they were to small.

 

[Jraef]

Are you sure it's Part Winding and not 2 speed? Usually there is only one OLR on a PW starter.

My bad. It's been so long since I used PW starting for anything that I forgot the circuit diagram. Never mind...

 

[masterinbama]

My bad. It's been so long since I used PW starting for anything that I forgot the circuit diagram. Never mind...

Jraef, don't feel bad I went the opposite direction and was thinking RVAT starters.

 

[wchild1520]

Try nec 430.4