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Star Delta

Can anybody explain star delta to me please? I understand that large motors are started by initiating in a star connection at a reduced voltage then switch over to delta but what is the reason?

Thanks

Reply 1

Popeye89

Think of star as a softer way of starting a motor. Less current and less torque until the motor is up to speed because it reduces the chance of damaging a machine by putting it under high load from idle, then switch to delta when its at or near to operating speed. Hope it helps.

Reply 2

gfunkmc

Thanks for your reply but what I was looking for was the reason a machine can't be started in delta? Any help would be appreciated!

Original post by Popeye89

Reply 3

Popeye89

Starting in star reduces the chance of damaging a machine. Say for example you have a 5KVA machine, starting in star will enable you to slowly build up to that where delta will ask for the whole lot straight away. Asking for all of it right away can cause excess wear and damage whereas easing it up to speed is better for the machine and the motor.