Getriebebau NORD explains slip and speed relationship in electric motors

Drive technology manufacturer Getriebebau NORD has provided an explanation of the relationship between slip and speed in electric motors, highlighting its impact on energy efficiency. The company states that the motor's speed reveals significant information about rotor losses, with slip being a direct measure of these.

Slip is calculated as the difference between the synchronous speed (field rotation speed) and the motor's nominal speed, divided by the synchronous speed. For instance, a motor with a synchronous speed of 1,500 rpm and a nominal speed of 1,460 rpm has a slip of 2.67%. This slip directly reflects the proportion of air gap power lost in the rotor.

NORD DRIVESYSTEMS points out that a low slip is characteristic of low-loss motors, meaning the actual speed is very close to the synchronous speed. An example given is a 4-pole, 3 kW IE3 motor achieving a nominal speed of 1,460 rpm with a slip of 2.67%, an improvement from an IE1 version which might operate at 1,415 rpm with 5.67% slip.

The company cautions that in applications like ventilation and pumping, increasing the motor speed might lead to higher energy consumption if the driven machinery is not adapted. This is because the power required for airflow can increase disproportionately with speed.