Electrical – Should startup torque be higher in value than full load torque in an induction motor

electricalengineeringinduction motor

I found out values of my 3 phase delta connected induction motor for full load torque, maximum torque and startup torque.

My maximum torque was higher than my full load torque, but the thing I'm wondering about is whether I'm right or not is that my startup torque is higher than my full load torque. Is that right, or is it supposed to be lower than full load? If it's supposed to be lower than it shows I need to look over my calculations again.

Full load torque= 25.68Nm

Max torque= 322.4Nm

Startup torque= 38.53Nm

Best Answer

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If 25.68Nm is your full-load torque, 38.53Nm (150%) as startup torque makes perfect sense for a Design A or Design B squirrel cage induction motor.

But a max or breakdown torque of 322.4Nm (1255%) is much too high, which should max out in the 200% to 250% range.

The torque the motor supplies depends upon the load. You'd have to compare your numbers to nameplate data to determine full-load torque.

$$T = \frac {9.55 P_m} {n}$$

Where T = Torque, \$P_m\$ = mechanical power out and n = speed in rpm.