Background

Wiring a Three Phase Distribution Board [DB] is of a necessity when the Power Distribution requirement cannot be handled by a Single Phase Power Supply. Since the Utility distributes power from a Three Phase Transformer, a prime requirement regarded by the Utility company is to make sure that the three phases of the transformers to be balanced in load distribution. Though a 100% balanced load cannot be achieved most of the time, a higher percentage of a balanced load is necessary for the transformer to give the highest efficiency. The consumer has an obligation to have his power utilization in the three phases to be balanced in a practically acceptable manner. He can achieve this by distributing his Single Phase power loads to the three phases so that a maximum possible load balancing will be achieved inside his premises. The example power distribution cited here for 3 Phases is based on the earlier Single Phase Consumer Unit wiring for ease of understanding.

Installation work described here is according to British Standards [ IEE Regulations and Practice ].

Accessory Requirement

12 Way Three Raw DB with facility to fix a 60A 3 Pole Moulded Case Circuit Breaker-01 nos

2 Pole-60A-30mA Trip Current RCD-03 nos

2 Pole -60A- MCB-03 nos

1 Pole-10A-MCB-15 nos

1 Pole -20A-MCB-6 nos

1 Pole-16A-MCB-3 nos

Cu MCB Bus Bar segment-8 way- 3 nos.

60A- 3 Pole MCCB [fixed type or Adj. Type ]

Bus Bar Link for Neutral Cable Connections

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Preparation

We are considering that the DB used here will power 5 nos. Lighting Sub Circuits,2 nos 13A Radial Circuits for Socket outlets and 01 nos. 16A Circuit for an AC units on each Phase.That is to say, here we are having a power utilization twice more than in the Single Phase power distribution. But we don't have any Three Phase loads (items using three phase power, for example. 3 ph motors etc) connected to this power distribution.

Method of Wiring

Sub Circuit wiring has been discussed in detail for 1W Light, 2W Light,5A ,13A and 16A Socket outlets etc. These needs to be wired prior to wiring of the DB unit so that when the DB is installed, these circuits can be connected to the DB.

DB Wiring and Installation.

The DB used will either be Surface mount or Flush Mount [ embedded] type. The enclosure will have entry points for connecting feeder cable and sub distribution cables on top and bottom sides. There will be many types of DBs in market but the example used here will enable the practitioner to handle any type with ease.The DB has a DIN rail for installing RCCB,and MCBs. It also has four Cu Connector Bars , three for connecting Neutral cables of the sub circuits of Red, Yellow and Blue phases separately and the other to connect all Earth cables used in socket outlets and electrical lighting fixtures etc. Compare the earlier single phase DB wiring with this one. You will see the similarities between the two in sub circuit wiring.

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