B.TECH - Semester 5 synchronous machines Question Paper 2020 (feb)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- What are the advantages of rotating field armature in $3 \phi$ alternators?
- Discuss the effect of pitch factor and distribution factor on generated e.m.f. of an alternator.
- How slip test is used for finding $X_{d}$ and $X_{q}$ of synchronous machine?
- What is short circuit ratio of synchronous alternator?
- What is Blondel's two reaction theory?
- Differentiate between EMF and MMF methods for finding regulation of an alternator.
- List out the advantages of parallel operation of alternators.
- How to safety disconnect one 3 phase alternator which is running in parallel operation with two or more alternator?
- Name the different methods for starting a synchronous motor.
- What is power angle diagram in connection with synchronous motor? ( $\mathbf{1 0} \boldsymbol{\times} \mathbf{2} \boldsymbol{=} \mathbf{2 0}$ Marks) P.T.O. Answer one full question from each Module.
- (a) What are the advantages of short chorded winding?
- (b) With a neat diagram explain the constructional features and working of a cylindrical pole synchronous alternator, Also write the emf equation of $3 \phi$ alternator. OR
- (a) Derive the EMF equation for a $3 \phi$ synchronous alternator.
- (b) A $3 \phi$ star connected armature on open circuit is required to generate a line voltage of $3.4 \mathrm{kV}, 50 \mathrm{~Hz}$, when driven at 500 rpm . The stator has 3 slots per pole per phase and 10 conductors per slot. The coils are short ch...
- (a) Discuss the merits and demerits of EMF, MMF and ZPF methods for calculating percentage voltage regulation of a synchronous machine. Very briefly describe ASA method for finding regulation?
- (b) A star connected $3 \phi$ alternator produces a current of 250 A on short circuit and a generated emf of 1500 V on open circuit. The effective armature winding resistance is $0.2 \Omega$ per phase. Calculate the voltage regulation when a load of ...
- (a) Explain armature reaction and its effect on $3 \phi$, alternator. What are the methods adopted to reduce the armature reaction effect?
- (b) The following data were obtained for the OCC of a $10 \mathrm{MVA}, 13 \mathrm{kV}, 3 \phi$ star connected synchronous generator. | Eo-Line (kV) | 6.2 | 8.7 | 10.5 | 11.8 | 12.8 | 13.2 | 14.2 | 15.2 | 15.9 | | :--- | :--- | :--- | :--- | :--- | ...
- (a) Discuss the effect of
- (i) Change in excitation, (ii) Change in input power, when alternators are running in parallel.
- (b) A $3 \phi$ star connected synchronous generator supplies current of 10 A having phase angle of $20^{\circ}$ lagging at 400 V . Find the load angle and components of armature current $\mathrm{I}_{\mathrm{d}}$ and $\mathrm{I}_{\mathrm{q}}$ if $\mat...
- (a) Explain with a neat diagram the bright lamp method for synchronizing a three phase alternator with infinite bus.
- (b) Two single phase alternators operating in parallel have induced emf on open circuit of $230 \angle 0^{\circ}$ and $230 \angle 10^{\circ}$ Volts and respective reactances of $\mathrm{j} 2 \Omega$ and $\mathrm{j} 3 \Omega$. Calculate (i) Terminal V...
- (a) Derive the power flow equation for a salient pole synchronous motor. Also draw the Power Vs Power angle diagram.
- (b) A star connected $3 \phi 6.6 \mathrm{kV}, 50 \mathrm{~Hz}$ synchronous motor takes 50 A current. The resistance and synchronous resistance and reactance per phase are $1 \Omega$ and $20 \Omega$ respectively. Find the power supplied to the motor a...
- (a) Write short notes on
- (i) ' V ' and 'inverted V ' curves of synchronous motor, (ii) Hunting in synchronous machine.
- (b) A $2300 \mathrm{~V}, 3 \phi$ star connected synchronous motor has a resistance of $0.2 \Omega$ per phase and a synchronous reactance of $2.2 \Omega$ per phase. The motor operating at 0.5 pf leading with a line current of 200 A . Determine the val...