Why does a star delta motor run at a very slow speed on delta after changing from star to delta?

There could be several different reasons for a motor to run slower than it should do after it has been switched over from star to delta connection.

Here are some possible reasons, but there may be others:

• its star-delta starter unit has a fault or has some bad external connections
• a broken or disconnected phase winding (or windings) inside the motor's frame.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.