Three(3) Phase to Single Phase Distribution Board Wiring Diagram

Three-phase to single-phase distribution boards are used to distribute electrical power to the single-phase loads from a three-phase input power source. Here, basically, the three-phase input power is plotted and distributed to the multiple loads. This type of distribution board is used in industrial and commercial buildings such as Schools, colleges, Hospitals, manufacturing plants, and factories for lighting circuits, and utility devices.

The Three Phase to Single Phase Distribution Board is basically built with a 4 Pole MCB or RCBO (Main Breaker) for isolating the entire board and protecting against overloads/short circuits and the Single-Pole MCBs are used for individual circuit protection (one for each single-phase load). A Neutral Busbar or Neutral Link is used for distributing the neutral line to all single-phase circuits. and a Earth Busbar or Eart Link is used for connecting all the grounding wires.

Three(3) Phase to Single Phase Distribution Board Wiring Diagram

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

Devices used in the DB

RCBO(Residual Current Breaker with Overcurrent)

Modern Distribution Boards use RCBOs instead of using the combination of MCB and RCCB because it provides the facilities of both MCB and RCCB. In the three-phase to single-phase distribution board, the four poles RCBO is used where all the three phases and neutral go through the RCBO.

MCB(Miniature Circuit Breaker)

Generally, single-pole MCBs are used for the output loads. All three phases have an equal number of MCBs. For example, if the DB has eight MCBs then each of all three phases will be connected to eight MCBs. So, the total MCBs in the box will be twenty-four (24).

Neutral Link

A neutral link is used to distribute a neutral supply to all the output loads. When single-pole MCBs are used for output loads, the neutral wire of the loads is connected to the neutral link.

Earth Link

The earthing terminal of the power supply and loads are connected to the earth link. Sometimes the wire from the earthing pit is also directly connected to the earth link. Even the metallic body of the distribution panel is also connected to the earth link.

Connection Procedure

1. First of all, select MCB and RCBO Rating as per your load requirements.
2. Identify the input-output sides of the MCB and RCBO.
3. Also, identify the line and neutral terminals on the RCBO if it has.
4. Now connect all the there phases and neutral from the input power supply to the input of the RCBO.
5. Connect the L1(or R phase) terminal from the output of the RCBO to all the Single pole MCBs that you want to connect with the L1 terminal or R phase.
6. Connect the L2(or Y phase) terminal from the output of the RCBO to all the Single pole MCBs that you want to connect with the L2 terminal or Y phase.
7. Connect the L3(or B phase) terminal from the output of the RCBO to all the Single pole MCBs that you want to connect with the L3 terminal or B phase.
8. Connect the neutral wire from the output of the RCBO to the neutral link. If the DB has multiple neutral links then interconnect them with each other.
9. Connect the Earth Wire (it may come from the input power cable or Earth pit) to the Earth link. If the DB has multiple Earth links then interconnect them with each other.

Follow the below procedure if you use MCB and RCCB instead of RCBO,

1. Connect all three phases and neutral from the input power supply to the input of a 4-pole MCB.
2. Now connect the output of the 4-pole MCB to the input of a 4-pole RCCB.
3. Connect the neutral from the output of the RCCB to the neutral link.
4. Connect all three phases from the output of the RCCB to the single-phase MCBs by connecting an equal number of MCBs per phase.
5. Earthing connection is the same for both types of connection.

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