motor curves

[gronk2003]

Would it be safe to assume that if the nameplate data on 2 squirrel cage induction motors are the same as far as FLA, voltage, HP, SF, frame and design that the torque curves and thermal curves will be the same?

 

[electricpete]

No.

If it were the same manufacturer and manufacturer's model number, then probably yes. Otherwise, there can be differences.

BUT, given that you know the nameplate info, you can get from NEMA MG-1 some info on locked rotor torque, breakdown torque, locked rotor kva/hp etc.

There is a condensed version of mg-1 with this info available for free at the NEMA site.

 

[Marke]

Hello gronk2003

There can be very major differences between the curves and motor that appear to be very similar can be very different. The three main indicators that are generally available and will give an indication, are the Locked Rotor Current, Locked Rotor Torque and Full Load Speed. If these three figures are equal, then the chances are that the curves will be similar. A small change in the full load speed can indicate a major change to the torque and current curve.
Locked Rotor currents can vary from 400% to 1200% but generally lie in the 550% to 900% range. Locked Rotor torques lie in the 60% to 450% range but typically would be 100% to 250%. I have more information on my web site at

http://www.lmphotonics.com/m_control.htm

that give a little background to this.
Best regards



Mark Empson

http://www.lmphotonics.com