Automatic 3-Phase Induction Motor Starter

3 section induction motor starter typically uses star-to-delta converters. The mechanical device coils of the motor area unit connected in star configuration at the time of power-on and switched to delta configuration once the motor reaches 3/4th of its full speed, once the mechanical device coils have developed decent back magnetic attraction force (emf).

The 3 section induction motor starter circuit bestowed here offers 2 main advantages: single-phase interference and automatic star-to-delta conversion. It is used solely with those motors that area unit rated for affiliation in delta configuration at the given line voltage and that has each end of every of the 3 mechanical device windings on the market singly.

In the beginning, the road voltage is applied to at least one finish of every one of the 3 windings, with the opposite ends bridged along, effectively connecting the windings during a star configuration. beneath this affiliation, the voltage across the windings is 1/√3 of line-to-line provide voltage then this flowing through every winding is additionally reduced by this issue. Compared to delta affiliation, the resultant current flowing from the availability, as additionally the force, is reduced by an element of 1/3 during a star configuration. The relevant equations for star and delta connections are given within the box.

Induction motor basics

The AC induction motor, conjointly referred to as the coop motor, includes a straightforward cage-like rotor and a stator coil containing 3 windings. The dynamic field made by the AC line current within the stator coil induces a current within the rotor, that interacts with the sphere and causes the motor to rotate.

The base speed of the AC motor is decided by the number of poles designed into the stator coil windings and therefore the frequency of the AC input voltage. A load on the motor causes the motor to slide in proportion to the load.

Reverse and Forward Power and Control wiring diagrams

O/L = Over Load Relay
NO = Normally Open
NC = Normally Close
REV = Reverse 
FOR = Forward

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