Electrical Machines II

Explain the importance of physical arrangement of winding in stator.

Explain winding distribution factor.

Describe the effect of a constant magnetic field in AC machines.

Explain the effect of poor revolving magnetic field in AC machines.

Give the losses that effect the performance of Induction machine.

What do you understand by torque slip characteristics.

Give application of a single phase induction machine.

Give power range of working of single phase induction machine.

Give importance of V curve.

Give example of operation of parallel operation of alternators.

Give scope and outcome of the electrical machine - II.

By help of neat diagram explain the Air - gap MMF distribution of AC machine winding.

Explain the concept of three windings spatially shifted by 120 degrees.

Explain the working model of doubly fed induction machine.

Describe the double revolving field theory.

Explain the concept of load division in synchronous machine.

In a 6 pole, 3 phase, 50 Hz Induction motor with star connected Rotor, the rotor resistance per phase is $0.3\Omega$, the reactance at standstill is $1.5\Omega$ per phase and the e.m.f between the slip rings on open circuit is $175\text{ V}$. Calcualte : i. Slip at a speed of $960\text{ RPM}$. ii. Rotor e.m.f per phase. iii. Rotor frequency and reactance at speed of $950\text{ RPM}$.

a. A $3\varphi$, $50\text{ Hz}$ slipring induction motor gives a stand still open circuit voltage of $500\text{ V}$ between slip rings. Calculate the rotor current and power factor at (i) standstill and (ii) with a slip of $4\%$. The per phase rotor resistance and inductance are $0.2\Omega$ and $0.04\text{ H}$. b. By help of neat diagram explain the construction and working module of squirrel cage induction motor.

Design a single phase induction motor and explain its constriction feature and equivalent circuit diagram.

a. In a $2000\text{ V}$, single - phase synchronous generator, a full - load current of $100\text{ A}$ is produced on short - circuit by a field excitation of 2.5 and an emf of $500\text{ V}$ is produced on open - circuit by the same excitation. The armature resistance is $0.8\Omega$. Determine the voltage regulation when the generator is delivering a current of $100\text{ A}$ at (i) unity power factor, (ii) 0.71 power factor lagging ; and (iii) 0.8 power factor leading. b. Explain the concept of armature reaction in synchronous machine.

Describe and design (a) Sinusoidally distributed winding, (b) Winding distribution factor.

Write short notes on : a. Revolving magnetic field. b. Three Phase rotating magnetic field.