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SSC JE Electrical 2019 with solution SET-1
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Hunting occurs in a/an motor

Sudden changes of load on synchronous motors may sometimes set up oscillations that are superimposed upon the normal rotation, resulting in periodic variations of a very low frequency in speed. This effect is known as hunting or phase-swinging.

SSC JE Electrical 2019 with solution SET-1
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_______is a tube that brings water to turbines

Penstock

Penstock pipe is used to bring water from the dam to the hydraulic turbine.

Penstock pipes are made up of steel or reinforced concrete.

The turbine is installed at a lower level from the dam.

The penstock is provided with a gate valve at the inlet to completely close the water supply.

It has a control valve to control the water flow rate into the turbine.

SSC JE Electrical 2019 with solution SET-1
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The Norton’s current in the circuit shown below is

According to the Norton theorem, to find the Norton current, first remove the load resistance RL from the network terminals AB. Short circuit the terminals AB as shown in Figure calculate the current ISc or IN through the short circuit.

Now resistance of 150Ω will not show any effect in the circuit. So only resistance of 30Ω will be effective.

Norton current IN = 360/30

IN = 12 A

SSC JE Electrical 2019 with solution SET-1
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An alternator has 9 slots/pole. What is the value of the pitch factor if each coil spans 8 slot pitches

Coil Span = 8

Pole Pitch = 9 slots/pole

Slot angle (α) = 180° / Pole Pitch = 180°/9 = 20°

Pitch Factor = cos(α/2) = cos (20/2)

Pitch Factor = cos 10°

SSC JE Electrical 2019 with solution SET-1
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A coil is wound with 50 turns and a current 8A produces a flux of 200μWb. Calculate the inductance of the coil

The inductance of the coil is given by the relation

L = Nφ/I

Where

N = number of turns = 50

φ = flux = 200μWb

I = current = 8 A

L = 50 × 200 × 10−6 ⁄ 8

L = 1.25 mH