A three phase motor will give three times the power output when the stator windings are connected in delta than if connected in star, but will take 1/3 of the current from the supply when connected in star than when connected in delta. The starting torque developed in star is ½ that when starting in delta.
- A two-position switch (manual or automatic) is provided through a timing relay.
- Starting in star reduces the starting current.
- When the motor has accelerated up to speed and the current is reduced to its normal value, the starter is moved to run position with the windings now connected in delta.
- More complicated than the DOL starter, a motor with a star-delta starter may not produce sufficient torque to start against full load, so output is reduced in the start position. The motors are thus normally started under a light load condition.
- Switching causes a transient current which may have peak values in excess of those with DOL.
RSS Feed