15

16

17

18

19

20

b.

0 ப at ‏سے9‎ titime

a. Explain how sinusoidal voltages and currents are represented as phasor? (4) b. A Coil
of resistance 50 Q and inductance 100 mH is connected in series with a (6) capacitor of
500 BLF is connected across a 230 V, SO Hz ac supply. Find (i) Current through the coil
(ii) Power consumed (iii) Reactive power and (iv) Voltage across the coil. Also draw the
phasor diagram with voltage as the reference vector.
a. Prove the instantaneous power consumed by a pure capacitor is zero. (4) b. A series
LCR circuit which resonates at frequency 500 kHz has L=IOO pH, (6) R=25Q and
C=1000 pF. Determine (i) the Q-factor of the circuit (ii) the new value of C required to
resonate at 500 kHz when the value of L is doubled and the new Q factor.
PART-C
Answer two full Questions (17 or 18 and 19 or 20)
a. Derive the relation between Line and Phase Values of Voltage and Current for a (4)
delta connected system.
The load to a three phase power supply consists of three similar coils connected (6) in star.
The line currents are 25A and the kVA and kW inputs are 20 and 11 respectively. Find (i)
the phase and line voltages (ii) the reactive power input (ili) the resistance and reactance
of each coil.
OR
a. What is meant by phase sequence of a 3 phase system? (3) 0. Three identical coil having
resistance of 10 Q and an inductance 38.2 mH are (7) connected in delta across 400 V, 3
phase 50 Hz supply. Find wattmeter reading if two Wattmeter method is used to measure

total power.

With a neat sketch explain plate earthing indicating standard dimensions. (10)
OR

a. If an earth leakage is occurred in a domestic installation, which protective device (5)

will act? Explain the working of that device.

Give the schematic Layout of an LT Switch Board.