Master trip relay (86)

                 It is Voltage operated attracted armature type relay. It is used to trip the Circuit breaker along with main protection relay. Overcurrent, Earthfault relay cannot direct operate circuit breaker we need to use this relay between main relay and circuit breaker.

WHY? :- You have question that why to use this relay why we cannot trip the CB from direct main relay so reason is as below.

• This relay create isolation between main relays (OC/EF) and circuit breaker trip coil so if anything occur (trip coil short or anything unwanted at control voltage level) in circuit breaker side your main relay not get affected. Remember, Main protection relay is expensive than master trip relay.

• Master trip relay contact can easily carry current which need to trip the breaker. Your main relay made not to carry this current. 

• When fault came your circuit breaker tripped, you also need annunciation (buzzer and annunciator in window) that your some panel breaker tripped so for this wiring you need something which has no. of NO, NC Contacts. Your main Overcurrent relay (Electromagnetic type relay) has only 2 NO Contact.

• It has higher speed of operation, high mechanical stability of contacts and can operate without chattering. It's operating time is 10msec.

                     

             Below point is basic of relay which applies to every voltage operated attracted armature type relays so please note down it (May useful in your interview).

When relays operate you need to reset it to close the circuit breaker. Some relay HAND RESET type and some relays are SELF RESET type.

1. HAND RESET:- You need to reset by your self manually.
2. SELF RESET:-    When voltage came it pickup(Operate), when voltage goes it drop off (Normal condition).

        MASTER TRIP RELAY IS HAND RESET TYPE RELAY.       

Master trip relay in normal condition.

                   Above image shown pic of master trip relay with one coil which is rated at 30V DC means when it's coil get 30V DC it operate and it's all contacts are changeover.

Master trip relay in operated condition

                  You can see in operated condition of master trip relay, NO contact become close and NC contact become Open. Now to reset it, you need to lift up white color handle.

  

                     This video shows how you operate and reset master trip relay manually. I picked up it from YouTube you can see my other videos too.

Wiring diagram of Master trip relay

                       It has coil on 1 and 2 terminal. it has it's own NC contact in series with coil so when it operate NC became open and it's coil will cutoff from supply. It has 3 NO and 2 NC contact.

Some Facts:-

1. Master trip relay also known as lockout relay, Tripping relay.
2. It's ANSI code is 86.
3. VAJH 13. (VAJ is for tripping relay and H means Hand reset.)
4. Some time to increase No. of contact two coil master trip is used.

Master trip relay with two coils.

                    

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