Electrical Engineering ⇒ Topic : Ratings of Three-phase induction motors

RATINGS OF 3-PHASE INDUCTION MOTORS

Three-phase induction motors are rated in terms of the following :

1. Power output in kW
2. Speed
3. Voltage
4. Frequency
5. Phase (single or three)
6. Line current
7. Temperature rise in specified time.

If a motor is designed to be operated on more than one voltage or at more than one speed by reconnecting the winding, a connection diagram is also given on the name plate.

Class of motors A, B, C, D, E or F is also to be mentioned on the name plate.

• Standard types of squirrel cage motors are :
• Class A motors Low-impedance squirrel cage rotor motors.
• Class B motors High-reactance squirrel cage rotor motors.
• Class C motors High starting torque, low starting current-double squirrel cage motors.
• Class D motors High resistance squirrel cage rotor motors.
• Class E motors.
• Class F motors