Lab Report
1. OBJECTIVES
(a) To determine the equivalent circuit parameters of a 3-phase squirrel-cage induction motor from laboratory test data.
(b) To determine the performance characteristics of an induction motor under load conditions.
(c) To control the no-load speed of an induction motor.
2. INTRODUCTION
2.1 Three-phase squirrel-cage induction motors
An induction motor is a transformer with a rotating secondary winding. It has two essential components: an outer stationary stator and an inner rotating rotor. (Figure 1)
[pic]
Figure 1: Induction motor
The three-phase induction motors could be categorized into two main types according to the different rotors: the squirrel-cage induction motors and the wound induction motors.
The squirrel-cage induction motors are commonly used when the load requires little starting torque, such as lifts and fans, while the wound induction motors are necessary used when the load requires high starting torque.
The induction motor used in this experiment is a there-phase squirrel-cage induction motor.
2.2 Power converter
Since it is necessary to adjust the voltage magnitude according to maintain a constant air-gap flux, when the motor supply frequency is varies, a power-converter is used in the experiment
A power converter is power-electronics based device which can supple power with varied frequency. It first converts the normally available fixed frequency ac supply to a dc supply by using a rectifier. The dc supply is then converted to a variable-frequency ac supply, which can maintain a constant air-gap flux in the motor by an inverter.
2.3 Synchronous speed
When the balanced three-phase currents flow through three-phase stator windings of the motor, a rotating magnetic field or magnetic motive force (mmf) is produced. The speed of the rotating mmf is called the synchronous speed and it depends on the supply frequency and the number of the poles in the motor, as shown in equation 1. [pic]
(a) To determine the equivalent circuit parameters of a 3-phase squirrel-cage induction motor from laboratory test data.
(b) To determine the performance characteristics of an induction motor under load conditions.
(c) To control the no-load speed of an induction motor.
2. INTRODUCTION
2.1 Three-phase squirrel-cage induction motors
An induction motor is a transformer with a rotating secondary winding. It has two essential components: an outer stationary stator and an inner rotating rotor. (Figure 1)
[pic]
Figure 1: Induction motor
The three-phase induction motors could be categorized into two main types according to the different rotors: the squirrel-cage induction motors and the wound induction motors.
The squirrel-cage induction motors are commonly used when the load requires little starting torque, such as lifts and fans, while the wound induction motors are necessary used when the load requires high starting torque.
The induction motor used in this experiment is a there-phase squirrel-cage induction motor.
2.2 Power converter
Since it is necessary to adjust the voltage magnitude according to maintain a constant air-gap flux, when the motor supply frequency is varies, a power-converter is used in the experiment
A power converter is power-electronics based device which can supple power with varied frequency. It first converts the normally available fixed frequency ac supply to a dc supply by using a rectifier. The dc supply is then converted to a variable-frequency ac supply, which can maintain a constant air-gap flux in the motor by an inverter.
2.3 Synchronous speed
When the balanced three-phase currents flow through three-phase stator windings of the motor, a rotating magnetic field or magnetic motive force (mmf) is produced. The speed of the rotating mmf is called the synchronous speed and it depends on the supply frequency and the number of the poles in the motor, as shown in equation 1. [pic]