peak vs stall torque

[bboggess]

I have noticed some servo motors have a peak and stall torque rating. Can someone explain to me the difference between peak and stall torque? doesn't a motor stall when it reaches peak torque?

[Mariss Freimanis]

It's a bad choice of terms but it is a standard.

Maximum Continuous Stall Torque: This is actually the maximum continuous torque rating for a motor. The emphasis is on 'continuous' as in 'do not exceed except for short periods of time'. You do, you burn your motor down.

Peak Stall Torque: This is the torque the motor will deliver if its shaft is prevented from turning. This is a more impressive number so manufacturers and vendors tout it.

Typically Peak torque is 5 to 10 times greater than Continuous torque. Current is directly proportional to torque so peak current is 5 to 10 times the continuous rating.

Motor heating goes up with the square of the current, being primarily 'I-squared-R'. This means the motor will develop between 25 times to 100 times more heat than it can safely dissipate while delivering peak stall torque. Not a good thing; keep your load at or below the max continuous torque limit.

Mariss

Mariss

[Evodyne]

Originally Posted by bboggess I have noticed some servo motors have a peak and stall torque rating. Can someone explain to me the difference between peak and stall torque? doesn't a motor stall when it reaches peak torque?

Hi! Take a peek at this thread. where the same discussion is going on with respect to sizing power supplies. We've played with the specs from a user's servo motors and it illustrates exactly what Mariss said.

Lance

[bboggess]

Makes sense. Thanks for the explanation.