Three(3) Phase Distribution Board Wiring Diagram and Connection

Hey, in this article we are going to see the Three(3) Phase Distribution Board Wiring Diagram and Connection Procedure. Three phase distribution board is used to distribute power to the three-phase loads and circuits such as three-phase motors, three-phase machinery, three-phase to single-phase distribution boards, etc. Three-phase distribution boards are used in large factories, buildings, manufacturing units, etc.

Three(3) Phase Distribution Board Wiring Diagram

Here, you can see the Wiring Diagram of the Three(3) Phase Distribution Board.

Devices used in the DB

MCCB(Molded Case Circuit Breaker)

MCCB is a protective device that can give protection against Overcurrent faults and Short circuit faults like MCB. MCB can be used for lower voltage and current ratings but MCCB is designed for high voltage and high current circuits and installations. In the 3-phase distribution box, the MCCB is used as the main switch.

MCB(Miniature Circuit Breaker)

In the three-phase distribution box, 3 pole MCBs are used for the output loads. Only Line terminals go through the MCBs.

RCCB(Residual Current Circuit Breaker)

Sometimes RCCBs are used in the 3-phase distribution board if required. RCCB is connected after the main MCCB. And the output from the RCCB is connected to the output MCBs. 

Busbar

Busbar is very important for 3 phase distribution box because here we cannot use normal wires for the connection as the voltage and current are very high. Busbar is used to connect the MCBs with the main MCCB.

Earth Link and Neutral Link

Earth links and Neutral Links are used to distribute the earthing and neutral connection to the loads.

Connection Procedure

1. First of all, select the ratings of the MCCB and MCBs as per your load requirements.
2. Identify the input and output terminals of the MCCB and MCBs.
3. Connect all three phases from the input power supply to the input of the MCCB.
4. Connect the output of the MCCB to the input of all the MCBs.
5. Connect the neutral wire from the input power supply to the neutral link. If the DB has multiple Neutral links then connect all the neutral links together.
6. Connect the earth wire (which may come from the input power supply or direct from the earth pit) to the earth link. If the DB has multiple Earthing Links then connect all the earth links together.
7. Now connect all three phases of a load to the output of the 3 pole output MCB in the DB. If the load has neutral then connect the neutral of the load to the neutral link in the DB. Connect the earthing wire of the load to the earth link in the DB.

If the Distribution Box has RCCBs,

1. As you see in the above wiring diagram, MCBs are installed in such a way that it has two sides. The left side has four MCBs and the right side has four MCBs. Here we have not used any RCCB.
2. But if there is a requirement this type of DB uses two RCCBs one for the left side and another for the right side. All the left-side MCBs are connected to the left-side RCCB and all the right-side RCCBs are connected to the right-side RCCB.
3. Both of the RCCBs are connected to the output of the Main MCCB. In this case, the total of both RCCB current capacities should be equal to or higher than the Main MCCB current capacity.

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