PHASE SEQUENCE DETECTOR {CIRCUIT LOGIC}

In a three-phase system, three circuit conductors carry three alternating currents (of the same frequency) which reach their instantaneous peak values at different times. Taking one conductor as the reference, the other two currents are delayed in time by one-third and two-thirds of one cycle of the electrical current.

The circuit logic is based on this phase difference. The first supply line, line L1, is taken as reference and is called R phase. Now the microprocessor checks which line reaches its peak value next, L2 or L3. If it’s L2 second line is called Y phase and the sequence is RYB. If it’s L3 then third line is Y phase and the phase sequence is RBY.