1. Order of the circuit is the number of memory elements present in the circuit.
A. True
B. False
Answer: A
The order of the circuit is the number of memory/storing elements that are non-separable present in the circuit. Examples of memory elements are capacitors and inductors.
2. In Induction motor rotor laminations are thicker than stator laminations.
A. True
B. False
Answer: A
The lamination thickness depends upon the frequency. The rotor frequency is s×f where f is stator supply frequency. The rotor laminations are thicker than stator laminations because rotor frequency is less.
3. Choose the Induction motor with peak speed.
A. 10 Pole
B. 12 Pole
C. 14 Pole
D. 16 Pole
Answer: A
The synchronous speed of the Induction motor is
Ns=120×f÷P.
Ns∝(1÷P).
The synchronous speed is inversely proportional to the pole. The maximum speed will be achieved with a minimum number of poles.
4. Which starting method is the best method for Induction motor?
A. Direct online starting
B. Autotransformer starting
C. Reactance starting
D. Star-Delta starting
Answer: D
The Star-Delta starting method is one of the best methods for starting the Induction motor. This method is cheaper and the line current in the star is 1÷3 times of in delta connection.
5. Induction motor is analogous to __________
A. Transformer
B. DC machine
C. Synchronous motor
D. Synchronous generator
Answer: A
The Induction motor is analogous to the transformer. It is also known as a rotating transformer. Both work on the principle of electromagnetic induction.
6. Which type of Induction motor is best for the pole changing method?
A. SCIM
B. WRIM
C. Single-phase IM
D. Linear IM
Answer: A
Pole changing method is used to control the speed of the Induction motor. It is only applicable for SCIM because the SCIM rotor is made up of aluminum, and copper bars.
7. _________ motor operates at high power factor.
A. Capacitor start
B. Capacitor run
C. Shaded pole
D. Reluctance
Answer: B
In the capacitor run, the capacitor is permanently connected with auxiliary windings. The capacitor is used for reactive power compensation. It improves the power factor of the machine.
8. The use of the capacitor banks in the 3-phase Induction motor is ________
A. To increase the power factor
B. To decrease the speed
C. To increase the speed
D. To decrease the power factor
Answer: A
Capacitor banks are used with a 3-phase Induction motor in order to improve the power factor of the machine. The inductor motor generally operates with a .6-.8 power factor range.
9. The concept of the slip is used in ___________
A. Synchronous machine
B. Induction machine
C. DC machine
D. Transformer
Answer: B
The slip in the Induction motor is s = Ns-Nr÷ Ns.
The slip existence is due to the relative speed between the stator magnetic field and rotor.
10. Which type of Induction motor is best for the e.m.f injection method?
A. SCIM
B. WRIM
C. Single-phase IM
D. Linear IM
Answer: B
The E.M.F injection method is used to control the speed of the Induction motor. It is only applicable for WRIM because the WRIM rotor consists of copper windings connected in a star connection. The external e.m.f can be connected with it using the slip rings.
