1.
Explain the voltage /frequency control of an induction motor drives
2.
Explain the closed loop speed control of CSI fed induction
motor drive.
3. With necessary diagram explain the vector control of
induction motor drive.
4. Explain constant air gap flux based closed loop v/f control
technique of induction motor drive in detail with neat sketch and necessary
equations.
5. Make a detailed
comparison between VSI and CSI fed induction motor drives
6. Explain in detail the static rotor resistance control in the
induction motor drive.
7. Explain about VSI induction motor drive and also closed loop
control for VSI induction motor drives.
8. Highlight the features of an induction motor fed from a
square wave inverter.
9.
Write a short notes on
energy efficient drives
Energy saving is achieved by operating the induction motor at
optimum voltage values. The energy saving depends on the following factors.
i) Duty cycle of motor: Energy saving is larger in drives
which operates at low duty cycle.
ii) Operation with overvoltage’s:
iii) Quality of motor design
iv) Over sizing of motor
10. A three phase 60 KW, 4000 rpm, 460 V, 60 Hz, 2 pole star
connected induction motor has the following parameters. Rs = 0.2 Ω Rr=0.28Ω,
Xs=0.3Ωand Xm=11Ω. The motor is controlled by by varying the supply frequency.
If the breakdown torque requirement is 70 Nm. calculate supply frequency and
speed ωm at the maximum torque.
11. A 2.8 KW, 400 V,50 Hz,4pole 1379 rpm, delta connected
squirrel cage induction motor has following parameters referred to the stator
Rs = 2 Ω, Rr =5 Ω, Xr=5 ΩXm =80 Ω. Motor speed is controlled by stator voltage
control. When driving a fan load it runs at rated speed and rated voltage. Calculate motor terminal voltage, current and
torque at 1200 rpm.
12. A 3 phase, 50 Hz induction motor has the following parameters
for its equivalent circuit R1=R2=0.02 Ω and X1=X2=0.1 Ω is to be operated at
one half of its rated voltage and 25 Hz frequency. Calculate i) the
maximum torque at this rated voltage and
frequency operation in terms of its
normal value and ii) the starting torque at this reduced
frequency and voltage in terms of its normal value.
13. Explain the four modes
of operation of a static scherbius drive 16
14. Why a cycloconverter
fed induction motor drive is preferred over inverter
controlled synchronous motor
drive for low speed applications
15. Explain the stator voltage
control of induction motor drive 
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