Page 108 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

Operation
• When the start button S2 is pressed the contactor coil K3 energised through P4, P3 and K1 normally closed
contact 12 and 11. When K3 closes, it opens the normally closed contact K3 closes it opens the normally close
contact K3 between 11 and 12 and makes contact between 10 and 9 of K3. Once K1 energises the NO contact
K1 point 8 and 7 establishes a parallel path to K3 terminal 10 and 9.
• The star contactor K3 remains energised so long as the start button is kept pressed. Once the start button is
released, the K3 coil gets de-energised. The K3 contact cannot be operated because of the electrical interlock
of K1 and normally closed contacts between terminals 12 and 11.
• When K3 contactor get de-energised the normally closed contact of K3 between terminals 11 and 12 established
contact in the contactor K2 coil circuit. The delta contactor K2 closes.

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CITS : Power - Electrician & Wireman - Lesson 70-75 CITS : Power - Electrician & Wireman - Lesson 70-75