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. 

PHASE SEQUENCE DETECTOR {Abstract}

The instrument presented here, the PHASE SEQUENCE DETECTOR WITH MOTOR ROTATION SELECTOR permits the electrical contractor or industrial maintenance electrician to permanently connect and tape the terminals of the motor being installed, without having to first energize the motor by a temporary hookup from a power source, if available, to determine motor rotation.

 Therefore, this relay instrument eliminates the need for temporary connections that can be time consuming, costly and quite hazardous, particularly where many large, high-voltage motors are involved. Also, certain types of drives should never be rotated in the wrong direction. In such cases, the temporary hookup or trial method, having a fifty-fifty chance of being wrong, can do serious harm.