Types of D.C. Distributors - In Short

The most general method of classifying d.c. distributors is the way they are fed by the feeders. On this basis, d.c. distributors are classified as:

• Distributor fed at one end
• Distributor fed at both ends
• Distributor fed at the centre
• Ring distributor.

Distributor fed at one end.

DC Distributor fed at one end

• In this type of feeding, the distributor is connected to the supply at one end and loads are taken at different points along the length of the distributor.
• The current in the various sections of the distributor away from feeding point goes on decreasing. Thus current in section AC is more than the current in section CD and current in section CD is more than the current in section DE.
• The voltage across the loads away from the feeding point goes on decreasing.
• In case a fault occurs on any section of the distributor, the whole distributor will have to be disconnected from the supply mains. Therefore, continuity of supply is interrupted.

Distributor fed at both ends.

DC Distributor fed at both ends

• In this type of feeding, the distributor is connected to the supply mains at both ends and loads are tapped off at different points along the length of the distributor.
• Here, the load voltage goes on decreasing as we move away from one feeding point say A, reaches minimum value and then again starts rising and reaches maximum value when we reach the other feeding point B. The minimum voltage occurs at some load point and is never fixed. It is shifted with the variation of load on different sections of the distributor.
• If a fault occurs on any feeding point of the distributor, the continuity of supply is maintained from the other feeding point.
• In case of fault on any section of the distributor, the continuity of supply is maintained from the other feeding point.
• The area of X-section required for a doubly fed distributor is much less than that of a singly fed distributor.

Distributor fed at the centre.

DC Distributor fed at centre

• In this type of feeding, the centre of the distributor is connected to the supply mains. It is equivalent to two singly fed distributors, each distributor having a common feeding point and length equal to half of the total length.

Ring mains.

Ring Distributor

• In this type, the distributor is in the form of a closed ring. It is equivalent to a straight distributor fed at both ends with equal voltages, the two ends being brought together to form a closed ring. The distributor ring may be fed at one or more than one point.

Use of DC Distribution

D.c. supply is required for the operation of variable speed machinery (e.g. d.c. motors), electrochemical work and electric traction. For this purpose, a.c. power is converted into d.c. power at the sub-station by using converting machinery e.g. mercury are rectifiers, rotary converters and motor-generator sets. The d.c. supply from the sub-station is conveyed to the required places for distribution.

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