Starting of squirrel cage induction motor

Also lets get to know the methods which are used to control the speed of squirrel cage. Know how the speed control is easily achieved by changing the number of . It is not desirable to start large motors direct on line (giving full voltage to the stator). For reduction in the starting current, a lower voltage is applied to the stator, especially for the squirrel cage induction motors. Full voltage is only applied when the .

NEMA has adopted standard requirements for the minimum starting capabilities of integral and large squirrel cage induction motors.

In order to understand the wye-delta motors and wye start delta run motors, we should discuss motor connection and starting terminology as applied to three phase motors.

This starting method is referred to . These methods are sometimes called as reduced voltage methods for starting of squirrel cage induction motors. Starting of squirrel cage motors. For this purpose, following methods are used: By using primary resistors . The three most common starting methods for squirrel cage motors are PWS (part winding start ), WDS (wye-delta start ), and electronic soft- start. Each serves approximately the same purpose but is dependent upon the number of contactors provided. Each also serves to energize the windings and gradually bring it to the run . This is assuming that the power supply can easily deliver the high starting current and that the power transmission components and the working machine are suitable for the high starting . We use starters in order to limit the high starting current.

We use different starters for both the type of three phase induction motors. Let us consider first squirrel cage type of induction motor. Induction motors can be started Direct-on-Line (DOL), which means that the rated voltage is supplied to the stator, with the rotor terminals short-circuited in a . In this metho a solid state variable frequency inverter is used to start the motor. With the variable frequency power source, the motor can supply full load torque at full load current for the duration of the acceleration. The initial applied frequency is very low, and the frequency is gradually increased to the running speed . The transformer action reduces the voltage applied to the motor terminals . Because of the transformer action, the line current is less than the motor current.

The impedance seen by the power system then is that of the reactance plus that of the motor. Effectively, the voltage is reduced by 1. For slip-ring motors- rotor resistance starting. For squirrel - cage motors - Direct-on -line starting - Star-delta starting . With line voltage applied to the motor, the current can be anywhere between four and ten times the motor full-load current. The light intensity of the bulbs is proportional to the current that flows through the motor. Part of the Bachelor of Science Final Project written by Bence.

Three-phase squirrel - cage induction motors are used widely for various purposes. However, their starting currents are so large that they have to be estimated accurately and proper mea- sures should be taken to prevent hazards caused by them. So far, the starting currents of the three-phase squirrel - cage induction motor .