# 3 Phase Induction Motor Speed Control Methods Pdf

## Speed Control of Three Phase Induction Motor

Direct on line starter is the simplest and inexpensive methods among all other methods for starting induction motor. Three phase Induction motor or Ac motor is started by itself but we require some starter or other methods for proper starting and controlling induction motor. There is one resistor connected between stator terminal and supply voltage. In slip ring induction motor, we can add external resistance in rotor circuit through slip ring and brushes.

## Explain Starting Methods of 3 phase Induction Motor

Such type of cascading is called cumulative cascading. In this methods, we provide a reduced voltage at the starting of the induction motor. As the other starter, the autotransformer starter is also used. Starting current and starting torque is obtained by correct tapping on autotransformer. In above, we saw three starters for effective starting of I.

This site uses Akismet to reduce spam. In this method of speed control of three phase induction motor external resistance are added on rotor side. The auxiliary motor is supplied with same frequency as the main motor i. Star-delta starter is a very common method for starting an induction motor. The speed control of three phase induction motor is achieved by current source inverter and cycloconverter.

The injected emf can either oppose the rotor induced emf or aids the rotor induced emf. So, we increase slip, which will further result in the decrease in rotor speed. Reliability and high efficiency.

Variable voltage variable frequency control. Therefore, a starter is provided in induction motor not for providing starting torque to induction motor but for protection of induction motor. But for supplying the same load, the torque must remains the same and it is only possible if we increase the slip and if the slip increase motor will run reduced speed. This type of method is bulkier and more expensive compared to another method. Therefore the efficiency of three phase induction motor is reduced by this method of speed control.

The speed of induction motor is given by, Where, N is the speed of the rotor of an induction motor, N s is the synchronous speed, S is the slip. But at the starting of the induction motor, starting current is very large which may damage motor windings. Starting current to the induction motor is reduced by applying reduced initial supply voltage.

In this method of speed control of three phase induction motor the original sinusoidal mmf wave is modulated by another sinusoidal mmf wave having the different number of poles. Here we will see a detailed article related to the starting methods of three-phase induction motor.

Star- delta starter figure is shown below. Motor gets a one-third current of the starting current.

Thus by adding additional resistance in the rotor circuit, do carmo differential geometry pdf we can decrease the speed of the three-phase *induction* motor. The equation of torque for three phase induction motor is The three-phase induction motor operates in a low slip region.

In this method of speed control of three phase induction motor, we provide two separate windings in the stator. Slip ring Induction Motor Fundamentals If you want to know about the slip ring induction motor.

The voltage source inverter provides variable voltage, variable frequency supply to the three phase induction motor. So for effective starting of the motor, Starter is provided in the motor. The equation above clears that if we decrease supply voltage torque will also decrease. Induction motor speed control by chopper.

Starting frequency is also controlled by this method. In a delta connection, motor gets full load current as required. These two stator windings are electrically isolated from each other and are wound for two different numbers of poles. This type of starter is suitable for both star and delta connection motor.

There is one more type of cascading in which the torque produced by the main motor is in opposite direction to that of auxiliary motor. But for supplying the same load, the torque must remain the same, and it is only possible if we increase the slip and if the slip increases the motor will run at a reduced speed. The main advantage of this type of speed control of three phase induction motor is that a wide range of speed control is possible whether it is above normal or below normal speed.

The induction motor is started by itself that we know. Here you can see at the time of starting, the starter is in star connection. Slip power recovery method.

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