INDUCTION MOTOR
Induction MotorsDemonstration file 


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Cherry Tree Scientific Software  Graham J. Rogers  Induction Motor Simulation
MENUDRIVEN GRAPHICAL USER INTERFACE (GUI) PROGRAMS by Prof. H.Sadat. The transformer program obtains the transformer equivalent circuit from opencircuit and shortcircuit tests. It also finds the transformer performance characteristics using the transformer parameters. In the induction motor program the parameters of the equivalent circuit can be entered on the circuit diagram. The program draws the Thevenin's equivalent circuit. Performance characteristics are then obtained for the specified slip and the torque slip curve is plotted on the screen. The analysis can be repeated for different slips. A GUI program deals with the design of a firstorder controller in the forward path of a closedloop control system. This GUI program designs the following controllers: Proportional, phaselag, phaselead, PD, PI, and PID controllers. To run the controller design program at the MATLABprompt type>> rldesigngui
Introduction to the concept of rotating magnetic field and production of rotating magnetic flux by twophase and threephase currents flowing through concentrated windings (1slot/pole/phase), magnitude & speed of resultant rotating flux, Constructional features of induction motors, threephase windings
Expression for the stator induced emf, principle behind the development of torque by the rotor, rotor frequency & slip.
Phasor diagram & equivalent circuit
Expressions for rotor current, establish the relationshiprotor input: copper loss: output1: s: (1s)
Effect of rotor resistance variation, maximum torque and the slip at which it occurs
No load and blocked rotor tests equivalent circuit parameters, circle diagram
Requirements to develop high starting Torque and reduced starting current, Deep bar and double cage rotors, Starters (stardelta, auto transformer & rotor resistance starters)
Braking of induction motor, induction generator
Double revolving field theory, Torque sped characteristics, equivalent circuit, Starting methods, auxiliary winding parameters for maximum starting torque, Characteristics of splitphase motor, capacitor start motor, two value capacitor motor, shaded pole motor
Induction
MotorsDemonstration file
Moduleg.xls
This module demonstrates the torque versus speed characteristics of a threephase induction motor. Draw the exact equivalent circuit of the motor and observe the effects of changing various parameters on the torque versus speed curve. In particular, vary the rotor resistance, applied voltage, and the supply frequency and observe the effects on the torquesped curves. Also verify whether the motor can supply a particular load. Draw two types of plots: torque versus slip and torque versus speed. The type of plot can be chosen by selecting the desired plot type from the plot pulldown menu under commands. There is a list of parameters of the induction motor that can be changed by clicking on the values and editing them to the desired values. The curve is updated by clicking on the calculate button. The curve is drawn for the displayed set of parameters.
(B) Rotor speed
(C) Greater than synchronous speed
Ans. (A)
(A) 940 RPM
(B) 1000RPM
(C) 1050 RPM
(D) 1100 RPM
Ans. (B)
(A) 8%
(B) 4%
(C) 2%
(D) 6%
Ans. (C)
(A)
Frequency
of rotor emf is too low
(B)
Flux
linking the rotor is of constant magnitude
(C)
Flux
density in the rotor parts is too low
Ans: (A)
(A)
5
kW
(B)
10
kW
(C)
20
kW
(D)
50
kW
Ans. (B)
(A)
5%
(B)
10%
(C)
25%
(D)
50%
Ans. (C)
(A)
0.2
(B)
0.7
(C)
0.85
(D)
1
Ans: (A)
8.The maximum torque
in a 3phase induction motor occurs at a slip
_{(A) }R_{2}/_{ }X_{2}
_{(B) }X_{2}/_{ }R_{2}
_{(C) }R_{2}^{2}/_{ }X_{2}
_{(D) }R_{2}^{2}/_{ }X_{2}^{2}_{}
Ans: (A)
9. For high starting
torque, the most 3phase induction motor is
(A)
Squirrelcage
type
(B)
Slipring
type
(C)
Deep
bar squirrelcage type
(D)
Doublecage
induction motor
Ans. (B)
10.
The
starting torque in a singlephase induction motor is
(A)
High
(B)
Low
(C)
Zero
(D)
Very
low
Ans. (C)
11.
The
efficiency of a singlephase induction motor as compared to a 3phase induction
motor rating is
(A)
Lower
(B)
Higher
(C)
Equal
Ans: (A)
_{ }
_{12. }_{The starting torque of a 3phase induction motor can be increased by increasing}
_{ }
_{ c ) the stator resistance}
Ans. B
13.
The maximum
starting torque in the induction motor is developed when the rotor reactance is
a)
half of the rotor resistance
b) twice of the rotor resistance
c) equal to the rotor resistance
Ans. C
14.
A change of
55 in the supply voltage of an induction motor will produce a change of approximately
a)
5%
b) 7%
c) 10%
d) 25%
in the rotor torque.
Ans. D
15. The
transformation ratio of an induction motor can be found by
a) blocked
rotor test
b) open
circuit test
c) slip
test
d) stator
resistance test
16. The
crawling in the induction motor is caused by
a) improper
design of the machine
b) low
supply voltage
c) high
loads
d) harmonics
developed in the motor.
Ans. D
17. Which
one of the following motors is most suitable for signalling devices and timers?
a) dc
series motor
b) ac
series motor
c) induction
motor
d) reluctance
motor
Ans. D