(a) Draw the diagram of a device which is used to decrease high S voltage into a AC voltage and state its working principle. Write four sources of energy loss in this device.
(b) A small town with a demand of 1200 kW of electric power at 220 V is situated 20 Km away from an electric plant generating power at 440V. The resistance of the two wire line carrying power is `0.5 Omega` per km. The town gets the power from the line thruough a 4000-220 V step-down transformer at s sub-station in the twon. Estimate the line power loss in the from of heat.

Explanation

Working principle: When the alternating voltage is applied to the primary, the resulting current produces an alternating magnetic flux in secondary and induces an emf in it. It works on the principle of mutual induction.
(i) Flux leakage between primary and secondary winding
(ii) Resistance of winding
(iii) Production of eddy current in iron core
(iv) Magnetization of the core
Total resistance of the line = `40xx0.5`
`=20Omega`
Current flowing in the line
`I=(P)/(V)`
`=(1200xx10^(3))/(4000)`
`300A`
Line loss in form of heat `=I^(2)R`
`=300^(2)xx20`
`=1800kW`