PTU B.Tech ECE 5th Semester May 2019 58025 INDUSTRIAL ELECTRONICS Question Papers

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Roll No. [] [] [] [] [] [] [] Total No. of Pages : 02

Total No. of Questions : 09

B.Tech.(EIE) (2011 & Onwards) (Sem.-5)

INDUSTRIAL ELECTRONICS

Subject Code : EI-309

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M.Code : 58025

Time : 3 Hrs. Max. Marks : 60

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.

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3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

1. Answer briefly :
   1. Differentiate between turn-On time and turn-Off time of SCR.
   2. What do you mean by PWM control strategy in chopper?
   3. Draw the two-transistor model of SCR.

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   4. Describe integral cycle control in brief.
   5. What do you mean by gate triggering and why it is preferred over other methods?
   6. Draw the circuit of singlephase parallel inverter and write down relation between output voltage and capacitor voltage.
   7. Draw and explain the V-I characteristics of SCR with proper labelling.
   8. A step-up chopper has input voltage of 220 V and output voltage of 660 V. If Ton time is 100 µs, Find out the pulse width of output voltage.

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   9. Which pulse rectifier has lowest value of ripple factor and why?
   10. Write down the basic performance equation for a separately excited dc motor.

SECTION-B

2. Draw the output voltage and current waveform for single phase symmetrical semiconverter with proper conduction status of thyristors and diodes for resistive load of R = 10O and input power supply of 230V. Also calculate the circuit turn off time of each components and average output current.

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3. A unijunction transistor, used in relaxation oscillator, has the following data :
   ?=0.67, I_p=10mA, V_v=25V, I_v=15 µA
   An oscillator with output frequency of 1 kHz is to be designed by using this UJT. Compute the value of charging resistor and external resistor needed in the base circuits. Take C = 0.4 µF and forward voltage drop of E-B₁ junction as 0.5V. Source voltage is 24V and triggering pulse width is 50 µs.
4. A single-phase unidirectional voltage controller is connected to a load R = 20O, input voltage is 230V, 50Hz. Firing angle delay is 60°. Determine
   1. rms and average output voltage
   2. input power factor

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   3. average diode current
   4. average thyristor current.
5. Explain with the help of circuit diagram and necessary timing waveforms, the working principle of a single-phase half bridge modified-series inverter.
6. A dc chopper is used to control the speed of a separately excited dc motor. The dc supply voltage is 220 V, armature resistance r_a = 0.2O and motor constant K_vf = 0.08V/rpm. This motor derives a constant torque load requiring an average armature current 25A. Determine
   1. the range of speed control

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   2. the range of duty cycle a. Assumed the motor current to be continuous.

SECTION-C

7. Describe in detail the operation of voltage commuted chopper with its relevant current and voltage waveforms as a function of time. The chopper operation may be divided into certain well defined modes. Enumerate the various simplifying assumptions made. Also find out the minimum permissible on-period in term of commutating parameters.
8. Describe in detail the operation of 3 phase full converter thyristor bridge with inductive load with relevant current and voltage waveforms for a firing angle of 30°. Also derive the expression of average output voltage.

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9. Write short notes on following :
   1. Cycloconverter.
   2. Pulse width modulation inverters.

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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