(a) Draw the diagram of a device which is used to decrease high ac voltage into a low ac voltage and state its working principle. Write four sources of energy loss in this device.
(b) A small town with a demand of of electric power at is situated away from an electric plant generating power at . The resistance of the two wire line carrying power is . The town gets the power from the line through a . step- down transformer at a sub-station in the town. Estimate the line power loss in the form of heat.
(a) A device which is used to decrease high ac voltage is known as a step- down transformer,
It works on the principle of mutual induction, It states that, if the current is changing through the primary coil, then there is a change in magnetic flux in the secondary coil. This change in flux induces an emf in the secondary coil.
The four sources of energy loss in the device are :
Flux leakage, eddy currents, Resistance of the windings and the hysteresis loss.
(b) Given,
The town has a power demand of at
Resistance per unit length
Length of each wire
Total resistance,
The transformers step down from to .
If there is no power loss in the transformers, then we can calculate the RMS current in the lines by :
The power loss in the lines is