Nominal Speed and Rated Current

Speaking of electric motors, nominal speed is the value of the speed (rpm) that the motor was designed to work with its nominal load, ie is the motor speed running at nominal power, under voltage and rated frequencies.

The speed of rotation of an AC motor depends on the frequency of the mains and the slip.

The nominal current is the current that the motor absorbs from the mains when the nominal power operates, under voltage and nominal frequencies. In order to calculate the nominal current of three-phase motors we must consider the mechanical power of the motor, the efficiency and the power factor.

In the starting current of electric motors, a high current will circulate in the stator winding which decreases as the motor speed increases.

It is common to find motors with starting current equal to 7 or 8 times the nominal current. On the nameplate of the motor, we have the necessary data that indicates how many times the starting current is greater than the rated current.

In order to reverse the direction of rotation of three-phase motors, simply reverse two phases that feed the motor.