STUPIDSID
Solve any four carry equal marks:-
1(a)
Explain connection and phasor diagram of Dy11 and Yy6 transformer.
5 M
1(b)
Explain crawling of Induction Motor with suitable diagram.
5 M
1(c)
Explain similarity between transformer and induction motor. Why induction machine called generalized transformer?
5 M
1(d)
Discuss double field revolving theory of single phase IM.
5 M
1(e)
Explain need of parallel operation of transformer and write necessary condition for parallel operation.
5 M
2(a)
What is switching inrush current? Explain Switching in phenomena in 3-phase transformer.
10 M
2(b)
A load of 1400 KVA at 0.866 pf lagging is supplied by two 3-phase transformer of 1000 KVA and 500 KVA operating in parallel. The ratio of transformation is same in both 6600/400 delta/star. If the equivalent secondary impedances are (0.001+j0.003) Ω and (0.0028+j0.005) Ω per phase respectively. Calculate power factor and load shared by each transformer
10 M
3(a)
Explain torque-speed characteristics of three phase induction motor and discuss the effect of Resistance on torque speed characteristics.
8 M
3(b)
A 15KW, 144 V, 4 pole, 50 Hz, 3-phase ster connected IM gave following test result:
Stator and rotor ohmic losses at standstill are assumed equal. Draw circle diagram for induction Motor and Calculate:
a) Line current power factor, slip torque, efficiency at full load
b) Max. Power output and max torque.
| Line Voltage | Line Current | Power Input | |
| No-load Test | 400V | 9A | 1310W |
| Block rotor Test | 200V | 50A | 7100W |
Stator and rotor ohmic losses at standstill are assumed equal. Draw circle diagram for induction Motor and Calculate:
a) Line current power factor, slip torque, efficiency at full load
b) Max. Power output and max torque.
12 M
4(a)
Explain need of starter for three phase IM and explain star delta starter in detail with Suitable diagram.
10 M
4(b)
Discuss V/F control method of speed control with speed-torque characteristics.
5 M
4(c)
A 3-phase, 6 pole, 50Hz induction motor has a full load speed of 960 rpm with its slip ring short circuited. The motor drive a constant torque load. Its rotor speed reduced to:
a) 800rpm &
b) 400 rpm by inserting external resistance in rotor, compare the rotor ohmic losses at these to reduce speed with that at full load.
a) 800rpm &
b) 400 rpm by inserting external resistance in rotor, compare the rotor ohmic losses at these to reduce speed with that at full load.
5 M
5(a)
Draw equivalent circuit diagram of single phase induction motor for no load & block rotor test and sind its parameters.
10 M
5(b)
Describe the principle of operation of Capacitor start and capacitor run induction motor along with torque speed characteristics. Draw circuit and phasor diagram and state the application.
10 M
Write short note on any two:
6(a)
Scott connection of three phase transformer.
10 M
6(b)
Induction Generator.
10 M
6(c)
Power flow of 3-phase induction motor.
10 M
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