* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download MEEPP 202 Electric Drives
Survey
Document related concepts
Power engineering wikipedia , lookup
Current source wikipedia , lookup
Commutator (electric) wikipedia , lookup
Electrification wikipedia , lookup
Buck converter wikipedia , lookup
Alternating current wikipedia , lookup
Voltage optimisation wikipedia , lookup
Three-phase electric power wikipedia , lookup
Distribution management system wikipedia , lookup
Electric machine wikipedia , lookup
Brushless DC electric motor wikipedia , lookup
Dynamometer wikipedia , lookup
Electric motor wikipedia , lookup
Brushed DC electric motor wikipedia , lookup
Induction motor wikipedia , lookup
Transcript
Reg. No: …..…………………. Name: …….………………... M.TECH. DEGREE EXAMINATION Model Question Paper - II Second Semester Branch: Electrical and Electronics Engineering Specialization: Power Electronics and Power Systems MEEPP 202 ELECTRIC DRIVES [Regular/Supplementary - 2011 Admission onwards ] Time: Three Hours Maximum: 100 Marks Answer all questions All questions carry equal marks 1. (a) Explain the steady state stability of a Motor-Load System with necessary equations and graphs. (15 marks) (b) Half hour rating of a motor is 100kW.Heating time constant is 80min and the maximum efficiency occurs at 70% of full load. Determine the continuous rating of the motor. (10 marks) OR 2. (a) A drive has following parameters :J=10kg-m2,T=(100-0.1N)Nm Passive load torque, Tl=(0.05N)Nm , where N is the speed in rpm. Initially the drive is operating in steady state . When it is reversed, motor characteristic is changed to T=(-100-0.1N) Nm. Calculate the time of reversal. (10 marks) (b) Derive the Moment of inertia of a flywheel to prove the load equalization. (15 marks) 3. (a) Explain with neat circuit diagram and waveforms, a three phase fully controlled dc motor drive. Get the expression for the average output voltage and speed. (10 marks) (b) The magnetization characteristics of a dc series motor when running at 500 rpm is given by Current(A) Emf(V) 20 215 30 310 40 381 50 437 60 485 70 519 80 550 Total resistance of the armature and field windings is 0.5 ohm. When connected for dynamic braking against an overhauling load of 500 Nm ,motor speed is to be maintained at 600 rpm. What resistance must be connected across the motor terminals? (15 marks) OR 4. (a) A 220 V, 960 rpm, 12.8A separately excited dc motor has armature circuit resistance and inductance of 2Ω and 150mH respectively. It is fed from a single phase half controlled rectifier with an ac source voltage of 230V,50Hz.Calculate i) Motor torque for α=60˚ and speed=600rpm.ii) Motor speed for α=60˚ and T=20 Nm. (15 marks) (b) Explain with neat circuit diagram and waveforms, a single phase half controlled dc motor drive. Get the expression for the average output voltage and speed. Draw the speedtorque characteristics. (10 marks) 5. (a) Analyze and compare the operation of an induction motor with balanced and unbalanced source voltages. (10 marks) (b) A 440V,50Hz,6 pole,950 rpm,Y-connected induction motor has the following parameters referred to the stator : Rs = 0.5Ω, Rr’ =0.4Ω, Xs=Xr’=1.2Ω ,Xm= 50Ω .Motor is driving a fan load, the torque of which is given by TL=0.0123ωm2 .Now one phase of the motor fails. Calculate motor speed and current. Will it be safe to allow the motor to run for a long period? (10 marks) (c) Derive the torque equation of a salient pole synchronous machine and draw the speed – torque characteristics. (5 marks) OR 6. (a) Explain the slip speed control of Induction motor with relevant equations. (10 marks) (b) The wound rotor motor is rated at 30kW,1170r/min,460V,60Hz.the open circuit voltage is 400V,the load resistance is 0.5 Ω. If the chopper frequency is 200Hz, calculate the time Ton so that the motor develops a torque of 200Nm at 900r/min. (10 marks) (c) With neat waveforms and circuit diagrams, explain electronic commutation of synchronous motor drive. (5 marks) 7. (a) Explain the closed loop speed control of load commutated synchronous motor drive. (10 marks) (b) Derive the no load speed equation of static Kramer drive. (15 marks) OR 8. (a) A 3-Ø SCIM drives a fan type load. No load rotational losses are negligible. Show that rotor current is maximum when motor runs at a slip s=1/3.Find also an expression for maximum current. (10 marks) (b) If 3-Ø SCIM runs at speed of (i)1450 rpm and (ii)1300 rpm, determine the maximum current in terms of rated current at these speeds. The IM drives a fan and no-load rotational losses are neglected. (15 marks) ***