B.TECH - Semester 8 power semiconductor drives Question Paper 2019 (nov)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Sketch the block diagram of an electric drive indicating each part. Give a brief explanation about each part.
- Differentiate between active and passive torque.
- Sketch the basic circuit configuration of a three-phase to single-phase cycloconverter with intergroup reactor.
- Name four applications of cycloconverters.
- Give reason why regenerative braking is not possible in DC series motors.
- Sketch the armature voltage and armature current waveforms of single-phase fully controlled bridge rectifier fed separately excited DC motor in discontinuous conduction mode.
- What are the advantages of chopper controlled DC drives over controlled rectifier fed DC drives?
- Name atleast four methods of speed control of 3-phase induction motors. Explain any one method. P.T.O.
- What are the advantages of static rotor resistance control over conventional rotor resistance control?
- What is the advantage of self-controlled mode over true synchronous mode of speed control of synchronous motors? ( $\mathbf{1 0} \boldsymbol{\times} \mathbf{4} \boldsymbol{=} \mathbf{4 0}$ Marks) Answer any one full questions from each Module.
- (a) Explain the steady state stability with an example.
- (b) A drive has following parameters:- $\mathrm{J}=10 \mathrm{~kg}-\mathrm{m}^{2}, \mathrm{~T}=100-0.1 \mathrm{~N}$ and $\mathrm{T}_{1}=0.05 \mathrm{~N}$ where N is the speed in rpm , Initially the drive is operating in steady state. Now it is to be ...
- (c) Describe the working of a single-phase to single phase abridge-type stepdown cycloconverter with RL load. OR
- (a) Explain the classification of load torques with necessary speed-torque characteristics.
- (b) A 3-phase, 100 kW , 6-pole, 960 rpm slip ring induction motor drives a load whose torque varies such that a torque of $3000 \mathrm{~N}-\mathrm{m}$ of 10 sec duration is followed by a torque of $500 \mathrm{~N}-\mathrm{m}$ of duration long enough...
- (c) Explain the working of a single-phase to single-phase step-up mid-point cycloconverter with R-load with necessary waveforms.
- (a) Describe the working of a single-phase fully controlled bridge rectifier fed separately excited DC motor in continuous and discontinuous conduction mode. Draw the armature voltage and current waveforms in both cases. 10
- (b) With a block diagram explain closed loop speed control of a separately excited DC motor above and below base speed.
- (a) Explain the working of a four quadrant chopper controlled DC motor showing the equivalent circuit in each quadrant.
- (b) A $220 \mathrm{~V}, 750 \mathrm{rpm}, 200 \mathrm{~A}$ separately excited DC motor has $\mathrm{R}_{\mathrm{a}}=0.05 \Omega$ Armature is fed from a 3-phase non-circulating current dual converter consisting of fully controlled rectifiers A and B. ...
- (i) Motoring operation at rated torque and 600 rpm (ii) Regenerative braking operation at rated torque and 600 rpm (iii) Motoring operation at rated torque and -600 rpm Regenerative braking operation at rated torque and -600 rpm .
- (a) Explain the working of a static Kramer drive (with diode bridge rectifier and inverter) for sub-synchronous speed control of induction motor. Also derive the expression for slip in terms of turns ratio of transformer and induction motor and firin...
- (b) Explain the speed control of a VSI fed 3-phase synchronous motor. OR
- (a) Describe $\mathrm{v} / \gamma$ method of speed control and rotor chopper speed control of a 3 phase induction motor.
- (b) A 3-phase, $440 \mathrm{~V}, 50 \mathrm{~Hz}$, 6-pole, Y-connected wound rotor induction motor has the following parameters: $\mathrm{R}_{\mathrm{s}}=0.5 \Omega, \mathrm{R}_{\mathrm{r}}^{\prime}=0.4 \Omega, \mathrm{X}_{\mathrm{s}}=\mathrm{X}_{\ma...
- (c) Describe the working of open-Loop inverter fed induction motor drive.