Three-Phase and Single-Phase Distribution Board
Figure 6 shows a small industrial distribution board. It is being used to supply a mixture of single-phase and three-phase circuits.
Single-phase Loads
It is supplying a single-phase lighting circuit and a single-phase motor circuit, both of which are not provided with RCD protection. It is also supplying two single-phase socket circuits, which are provided with RCD protection.
Three-phase Loads
It is supplying a three-phase motor circuit, which is not provided with RCD protection. It is also supplying a three-phase socket circuit, which is provided with RCD protection.
Neutral Connections
It is supplied with three neutral bars. It is of the utmost importance that the various circuit neutrals are not mixed up in any way. A wrong neutral connection will result in the tripping of one or other RCD.
It is possible to supply the single-phase loads through a three-phase RCD. This would simplify the arrangement a good deal, however it is not recommended to supply a mixture of single and three-phase loads through one RCD. The reasons for this are beyond the scope of Phase 2 of the apprenticeship.
The neutral connection for any load not protected by an RCD must be from the main neutral bar.
The neutral connection for any load protected by the single-phase RCD must be from the single-phase RCD neutral bar.
The neutral connection for any load protected by the three-phase RCD must be from the three- phase RCD neutral bar.
Note: There is only one circuit supplied through the three-phase RCD. The neutral connection for this circuit can be taken directly from the three-phase RCD, if a separate neutral bar is not provided.
Small Industrial Distribution Board
