HSDT2CO & BSDT
The HSDT2CO Series and BSDT Series are Star Delta Timers which have been designed specifically to meet the requirements for starting squirrel cage motors by star-delta change over. They have a run up time settable from 0-30 sec and give a fixed 50msec (40 to 70ms) changeover delay time. This changeover delay prevents the overlapping operation of star and delta contactors. This in turn prevents possible sparking, thus protecting contactors and motors from damage. The output is 1 NO contact each for star & delta relay for HSDT2CO series timer and 1 NO contact for BSDT series timer.
GE has the widest range of Power Contactor in India today (6A to 825A, AC3). To ensure trouble free and smooth operations of your star delta starters, insist on GE make CL & CK contactors with HSDT2CO Star-Delta Timer (with 2 changeover contacts) and BSDT Star-Delta Timer (with 1 changeover contact)
Operating Principle - Two changeover - HSDT2CO
Timer gets the supply as soon as switch S2 is closed. Star contact (15/18) of the timer closes which in turn gives supply to the star contactor K1 and the set runup time starts. At the same time mains contactor K2 is switched on via the auxiliary contact of star contactor K1 and then becomes self-holding via its own auxiliary contacts. Star contact of the timer opens at the end of run-up time, thus switching off the supply voltage of the star contactor. The second delay starts after star
contactor opens. At the end of this delay, the delta contact (25/28) of the timer closes, starting the delta contactor K3. The delta contactor, thereafter remains on until power is discontinued.
Operating Principle - One changeover - BSDT
Star contactor K1 closes and the set run-up time starts when the supply voltage is applied. Mains contactor K2 is switched on via the auxiliary contacts of star contactor K1 and then becomes self-holding via its own auxiliary contact 13/14. Simultaneously, auxiliary contacts 21/22 of mains contactor K2 open, thus connecting the star-delta timer and the star contactor via its auxiliary contacts 43/44 to the supply. Contacts 15/16 of star-delta timer open after the run-up time,
thus switching off the supply voltage of the timer and of the star contactor. Contact 15/16 of star-delta timer remains open for approx. 50msec and resets after that time to ensure that star contactor K1 has opened. Delta contactor K3 has been connected via auxiliary 22/21 of star contactor K1.