Electric Motors- Stall Time & Allowable Run Up Time

[PetroMech991]

What is the difference between stall time and max allwable run up time? I know stall is the max time time a motor can sustain the heat generated by the high inrush current without damaging the motor insulation. I can calculate the time the motor to accelerates the load to full load conditions. But what is it exactly?
Thanks Guys

 

[itsmoked]

Not completely clear on your two questions.

But 'your' stall time is not really normally used as it is very short. Often less than a second. So it's not a very useful number.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

thread238-207119

There was some discussion in this thread that may get you started.

Safe stall time is for locked rotor conditions. There are different times for hot versus cold start.

 

[7anoter4]

HI PetroMech991
stall time and starting time
I think this is very clear explained in:
"Motor Protection Application Considerations" by Basler :
When a motor stator winding is energized with the rotor stationary, stator winding currents may range from three to seven times rated full-load value depending on motor design and supply system impedance. Actual values of locked rotor currents are part of the motor data supplied by the motor manufacturer. Heating in the stator winding, proportional to I2t, is 10 to 50 times rated conditions and the winding is without benefit of the ventilation normally produced by rotation of the rotor.
Depending on the design, a motor may be stator limited (thermally) or rotor limited (thermally) during locked-rotor conditions. The motor manufacturer can furnish the allowable locked-rotor time only after the motor design is completed. This is given as time at rated lockedrotor current starting from either rated ambient temperature or rated operating temperature also referred to as cold stall time or hot stall time.
Starting times depend on motor design and load torque characteristics and must be determined for each application. Although starting times of 2 to 20 seconds are common, high inertia loads may take several minutes to bring to full speed. Starting time is increased if bus voltage is less than nominal.
See

http://www.basler.com/downloads/Motorconsid.pdf

Best Regards

 

[LionelHutz]

Stall time - The time the motor is allowed to operate at rated voltage with a locked rotor.

Max Allowed Run up Time - The max time the motor can take to accelerate a load from 0 to full speed when rated voltage is applied. I would also believe this number assumes a high inertia load that has a fairly linear acceleration.