3 Phase Induction Motor construction and working

 Classification of 3 Phase Induction Motor 

Three Phase Motors

3 Phase Induction motor are classified based on work voltage and manufacture there.

 

AC motor working principle-

1. HT Motor: - This motor works on high voltage 11 kv, 6.6 kv, etc. Typically, a motor above 500 kW comes with high-voltage winding. HT motors are used in very large industries such as exhaust fans for heavy loads, indexed draft fans, very large compressors, etc. 

These motors are of two types, the first being a synchronous motor. The synchronous motor stator consists of three-phase high voltage winding. The rotor is typically a sailor pole type with 200 to 300 amperes (1MW motor) with 4 poles (similar to stator winding), usually 24 to 50 volts DC.

 In addition to this DC winding rotor, there is also a fastener winding made of solid copper conductors on the rotor pole face. This sponge winding provides the starting torque to the rotor whi! E Starting and lowering motor hunting while walking. The power factor of a synchronous motor can be adjusted with the rotor current (excitation current), so these motors are also used for power factor correction purposes. The second is the simple induction motor.

2. LV Motors: - These motors are working on 415 blanks.

induction motor winding

Squirrel Cage Induction Motor: - This motor consists of 3 phase windings in the stator and one squirrel-cage winding in the rotor. Squirrel cage windings have solid conductors of copper or aluminum in the rotor slot with short-circuiting end rings on both sides. 

These motors are used directly on the line starter or star-delta starter. The starting torque of the motor is 350 percent of full load torque. These motors are used in industry in-floor mills, belt conveyors, ventilation fans, and compressors. These motors operate at almost constant speed near synchronous speed. Some double-speed motors also come. Squirrel cage induction motor speed control is performed with the help of variable voltage variable frequency drives.

Slip ring induction motor

This type of motor stator consists of 3 phase winding. The rotor also has a three-phase winding connected in a star connection. The three leads of the rotor winding are attached to a slipping mounted on the shaft. 

The outer connection of the slipping is given with the help of a carbon brush. The slipping motor consists of a 3-phase supply to the stator and a three-phase connected external resistance is inserted into the rotor circuit.

 At full starting resistance, the rotor is placed in the circuit as the speed increases gradually all the resistance is cut off which is the lower the external resistance is operational. The advantage of a slippering motor is that its maximum torque can be attained from the initial speed to the full load speed. Slippering motors are used in electrical.