Wednesday, April 16, 2014

Induction motors not kept running in Star Connections

Induction motors are not kept on running in Star connections due to following reasons:-

In Star connections, Phase current= Line current and

Phase voltage= Line voltage/ √3.

As Power = √3X Line Voltage XLine Current X Power Factor

This means that during starting voltage get reduced by factor 1/√3.
So current is also get reduced by factor 1/√3.
So Torque also gets reduced by factor 1/3 as Torque is directly proportional to square of voltage.
Due to reduced voltage Motor unable to take-up higher loads.

So motor power get reduced by 1/3 times then in Delta connections that is why motor is not kept running in Star connections. As motor is get under utilized.
So Motor will kept on running at reduced power and means motor will run at low efficiency