Locked Rotor Amps 3

[eng1561]

Is locked rotor amps proportional to FLA or any other motor attribute that would allow a quick estimate of this value? As far as I know, this is a value supplied by the manufacturer or performed as a start-up check for large motors. Any help would be greatly appreciated!

 

[DickDV]

It's highly dependent upon the NEMA Design letter and the NEMA Code letter marked on the motor nameplate.

See your engineering handbook for interpretation.

 

[eng1561]

DickDV,
Thank You! I never knew about this tid bit of information. I've followed up on what you recommended and it explains everything. Thanks again!

 

[GGOSS]

Hello eng1561,

Locked Rotor Current (LRC) and Locked Rotor Torque (LRT) are values that are influenced by the rotor design of the motor. The shape, position and material used to manufacturer the rotor bars are the key influencing factors.

Both LRC and LRT are expressed as a percentage of FLC (Full Load Current) and FLT (Full Load Torque.

Typical characteristics are as follows;

Nema Design A motors will have an LRC in the region of 800% FLC and a LRT in the region of 120% FLT.

Nema Design B motors will have an LRC in the region of 650% FLC and a LRT in the region of 180% FLT.

I hope the above helps.

Regards,
GGOSS