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Why are there 2 types of time delays on the LC3D star-delta starters?

To switch the motor from star to delta connection, the LC3xx star-delta starter must actuate its delta contactor with a slight delay after opening the star contactor to ensure adequate breaking time for the "star" contactor.

For contactors rated LC1D80 and below, the switching time of 40 ms +/- 15 ms between opening of the NC contact and closing of the NO contact on the LADS2 time delay module is sufficient to ensure this breaking time.

This is not the case for LC1D115 and LC1D150 contactors, the time provided by the LADS2 module is no longer sufficient and there will be a risk of short-circuiting.

The LADT2 auxiliary contact block combined with a CAD32 contactor relay inserted in the control section will ensure that the star contactor opens before the delta contactor closes.
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