Jawaharlal Nehru Technological University Hyderabad 2007-1st Sem M.Tech Power Electronics Code No: 52104/MT s, ruary-POWER ELECTRONIC CONTROL OF DC DRIVES - Question Paper

Here i am submitting M.Tech I-Semester Examinations, February-2007.POWER ELECTRONIC CONTROL OF DC DRIVES ques. paper in the provided attachment.

Code No: 52104/MT M.Tech I-Semester Examinations, February-2007.

POWER ELECTRONIC CONTROL OF DC DRIVES (Common to Power Electronics and Electric Drives, Power and Industrial

Drives and Power Electronics)

Time : 3 hours    Max. Marks : 60

Answer any FIVE questions All questions carry equal marks

1.a)    Explain the different modes of operation of I-phase fully controlled rectifier-fed separately excited motor for motoring mode of operation.

2.a)    The speed of a 150 HP, 650V, 1750 rpm, separately excited d-c motor is controlled by a 3-, full converter. The converter is operating from a 3-, 460 v, 50 HZ supply. The rated armature current of the motor is 170 A. The motor parameters are Ra=0.099 Q, La=0.73 mH, Ka=0.33 u/rpm. Determine

a)    No-load speed at tiring angle a=30⁰. Assume that at no load, the armature current is 10% of rated current and is continuous.

b)    The tiring angle to obtain rated speed of 1750 rpm at rated motor current. Also, compute the supply power factor.

3.    a) Draw the output voltage of 3- full bridge inverter for a tiring angle of

120⁰ considering DC motor as load? Assume continuous ripple free load current? Obtain the average output voltage expression.

4.a)    Draw the control schematic of a two quadrant three-phase converter-controlled DC motor Drive?

b) Discuss the control modeling of three phase converter?

5.    Explain the different current control schemes that are used for dc motor control.

6.a)    Explain the time ratio control, current limit control in case of chopper fed demotors.

b) Obtain the expression of ripple current for the ratio control.

7.a)    Discuss the Pulse Width Modulated (PWM) current control used in chopper fed demotor.

b) Obtain the Transfer function of current controller.

8.    Draw the flow chart for the dynamic simulation of chopper-controlled dc motor. Derive the necessary state equations.

AAA

Attachment: jawaharlal-nehru-technological-university-hyderabad-2007-m-tech-power-electronics-47017-1.pdf

Earning:   Approval pending.