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Poly Phase Induction Motor Question & Answers

September 27, 2021 By Wat Electrical Leave a Comment

This article lists 100 Poly Phase Induction Motor MCQs for Engineering Students. All the Poly Phase Induction Motor Questions & Answers given below includes solution and link wherever possible to the relevant topic.

The induction motor has two main parts they are stator and rotor, the stator is a three coil winding. The stator produces a rotating magnetic field when a three-phase current passes through the winding. The induction motors are widely used as industrial drives because they are rugged, economical, and reliable.

The word poly means two or many and the word phase means winding, the circuit which has more than two windings then the circuit is said to be a polyphase circuit. In polyphase windings, it is essential that the waveforms of the phase electromotive forces are identical and the frequency of the phase electromotive forces are equal.

1). The AC motors are categorized into _____________ types
HintThe AC motors are categorized into three types they are polyphase, universal, and single-phase

Read more about AC Motor

2). How many parts does the three-phase induction motor consist of?
HintThe three-phase induction motor consists of two parts they are rotor and stator
Read more about Three Phase Induction Motor
3). What are the main parts of the stator?
HintThe stator winding, stator core, and outer frame are the main parts of the stator
4). The cost of the wound motor is ____________
HintThe cost of the wound motor is more compared to other motors
5). The size of the wound motor is ____________
HintThe size of the wound motor is large
6). What is the standard form of RMF?
HintThe standard form of RMF is Rotating Magnetic Field
7). What is the standard form of LIM?
HintThe standard form of LIM is Linear Induction Motor
8). The induction motor frame is made up of ___________
HintThe induction motor frame is made up of cast iron
9). The induction motor shaft is made of _________
HintThe induction motor shaft is made of carbon steel
10). The slip is around _____________ in medium size induction motors
HintThe slip is around four percent in medium-size induction motors
11). Which one of the materials is used to made slip rings?
HintThe slip rings are made of phosphor bronze
12). ___________ are the types of poly-phase induction motor
HintThe wound rotor and squirrel cage machines are two types of poly-phase induction motor
13). The shaft speed parameter is defined as a ratio of _____________
HintThe shaft speed parameter is defined as a ratio of shaft speed divided by the synchronous speed
14). The ratio of synchronous speed divided by a rotor speed is known as ___________ speed
HintThe ratio of synchronous speed divided by a rotor speed is known as slip speed
15). Which one of the following is the correct formula for synchronous speed?
HintThe formula for synchronous speed is given by (120*frequency of the system)/P
16). Which one of the following is a correct formula a motor slip?
HintThe formula for motor slip is given by (Speed of magnetic field-mechanical shaft speed)/speed of magnetic field*100
17). The induced torque is defined as a ratio of ____________
HintThe induced torque is defined as a ratio of power in KW divided by the speed in r/min
18). The induction motor rotor runs at _____________ speed
HintThe induction motor rotor runs at below the synchronous speed
19). The induction motor torque is _____________ proportional to the slip
HintThe induction motor torque is directly proportional to the slip
20). The percentage slip in an induction motor depends on ___________ in motor
HintThe percentage slip in an induction motor depends on copper losses in the motor
21). If the air gap is increased in an induction motor, the power factor will be ____________
HintIf the air gap is increased in an induction motor, the power factor will be low
22). What are the disadvantages of LIM motor?
HintThe disadvantages of LIM motor are maintenance is not easy, power factor is very low, and capital cost is very high
23). What are the advantages of LIM motors?
HintThe linear induction motors are simple, more efficient, and has a lower initial cost
24). The starting torque is high in ____________ induction motor
HintThe starting torque is high in slip ring induction motor
25). The speed control by rotor resistance is possible in ___________ induction motor
HintThe speed control by rotor resistance is possible in slip ring induction motor

Polyphase Induction Motor MCQs for Exams

26). Which one of the following is a type of stator?
HintThe autotransformer stator, stator resistance, DOL, rotor resistance, and star-delta are the types of stators
27). What are the advantages of stator?
HintThe stators are cheap and simple in construction
28). Which one of the following stator costs is more?
HintThe auto-transformer stator cost is more compare to star-delta and DOL stators
29). Which one of the following stators doesn’t decrease the starting current?
HintThe direct on-line stator doesn’t decrease the starting current
30). The direct on-line stator is used up to _____________ HP
HintThe direct on-line stator is used up to 5 HP
31). Which one of the following stators used above 20 HP?
HintThe auto-transformer stator used above 20 HP
32). Which one of the following stators is very cheap?
HintThe direct on-line stator is very cheap compare to other stators
33). What are the advantages of auto-transformer?
HintTh auto-transformers have high efficiency, more VA rating, and has fewer copper losses
34). Which one of the following transformers is can’t be used as variac?
HintThe two winding transformers is can’t be used as variac
35). Which one of the following transformers has more KVA rating?
HintThe auto-transformer has more KVA rating compare to two winding transformer
36). Which one of the following costs is slightly higher?
HintThe slip ring cost is slightly higher compared to squirrel induction motor
37). The leakage and resistance values are more in _____________ transformer
HintThe leakage and resistance values are more in two winding transformer
38). How many windings do the two winding transformers have?
HintThe two winding transformers have two windings
39). The wound or slip ring rotor is used for ______________
HintThe wound or slip ring rotor is used for elevators, cranes, lifts, etc
40). The squirrel cage rotor is used for ______________
HintThe squirrel cage rotor is used for water pumps, lathes, fans, etc
41). The speed control by rotor resistance is not possible in ______________ rotor
HintThe speed control by rotor resistance is not possible in squirrel cage rotor
42). In squirrel cage rotor, the rotor copper losses are _____________
HintIn squirrel cage rotor, the rotor copper losses are less
43). The difference between rotor speed and synchronous speed of RMF is known as ______________
HintThe difference between rotor speed and synchronous speed of RMF is known as slip speed
44). Which one of the following system costs is high?
HintIn brushless DC motor, the system cost is high because of external controller requirement
45). In which one of the following motors the controller is required?
HintIn brushless DC motor, the controller is required to control the communication sequence whereas the controller is not required in brushed DC and induction motor
46). In which one of the following motors the speed range is low?
HintIn an induction motor, the speed range is low, whereas in a brushless DC motor the speed range is high
47). Which one of the following has less starting current?
HintThe slip ring induction motor has less starting current compare to the squirrel induction motor
48). How many windings does auto-transformer have?
HintThe auto-transformer has only one winding whereas the two winding transformers have two
49). The copper losses are more in ___________ transformer
HintThe copper losses are more in two winding transformers whereas in autotransformer the copper losses are less
50). The size and cost is high in _______________ transformer
HintThe size and cost is high in two winding transformer

Polyphase Induction Motor Important MCQs

51). Which one of the following transformers has less efficiency?
HintThe two winding transformers has less efficiency whereas in autotransformer the efficiency is high
52). In which one the following motor the special starting circuit is required?
HintIn induction motor the special starting circuit is required
53). The motor control is categorized into _____________types based on the functions served
HintThe motor control is categorized into three types based on the functions served they are motor protection, speed control, and torque control
54). What is the standard form of BLDC?
HintThe standard form of BLDC is Brushless DC Motor
55). What is the standard form of CPAP?
HintThe standard form of CPAP is Continuous Positive Airway Pressure
56). Which one of the following motors is a type of brushless DC motor?
HintThe interior permanent magnet type is one type of brushless DC motor
57). Which one of the following is not a type of DC motor?
HintThe synchronous motor is not a type of DC motor
58). Which one of the following motors has a fast dynamic response?
HintThe VR motor has a fast dynamic response whereas the PM motors have a slow dynamic response
59). Which one of the following motors doesn’t have detent torque?
HintThe VR motor doesn’t have detent torque whereas in PM motors the detent torque is present
60). Which one of the following motors has a high maximum stepping rate?
HintThe VR motor have high maximum stepping rate i.e around 1200 pulse per second
61). Which one of the following motors has a high step angle?
HintThe VR motors have high step angles whereas in PM motor very small step angle is possible
62). _________________ are the modes of operation of variable reluctance stepper motors
HintThe 1 phase ON, 2 phase ON mode, half step operation, and micro-stepping are the modes of operation of variable reluctance stepper motors
63). The low inertia DC motors are categorized into _______________
HintThe low inertia DC motors are categorized into two types they are shell-type motor and printed circuit motor
64). Which one of the following is denoted by CX?
HintThe control transmitter is denoted by CX, it is a type of synchro transmitter
65). Which one of the following is denoted by CD?
HintThe control differential is denoted by CD, it is a type of synchro differential
66). The synchros are used in servomechanism for _____________
HintThe synchros are used in servomechanism for error detection, torque transmission, subtracting and adding rotary angles
67). What is the standard form of SR motor?
HintThe standard form of SR motor is Switched Reluctance motor
68). The switched reluctance motor has power rating up to _____________
HintThe switched reluctance motor has a power rating of up to 75KW
69). The variable reluctance motor has ______________
HintThe variable reluctance motor has low a power rating and lower efficiency
70). What is the standard form of PMBL?
HintThe standard form of PMBL is Permanent Magnet Brush Less Machines
71). Which one of the following is a type of AC motor?
HintThe commutator motor, synchronous motor, and induction motor are the type of AC motors
72). The stepping motor is categorized into _________________
HintThe stepping motor is categorized into three types they are VR type, PM type, and hybrid type stepping motors
73). Which one of the following motors is not a type of induction motor?
HintThe reluctance motor is not a type of induction motor, it is a type of synchronous motor
74). The winding field DC motors are categorized into _______________
HintThe winding field DC motors are categorized into three types they are shunt motor, series motor, and separate field motor
75). The surface permanent magnet type motor is a _______________ motor
HintThe surface permanent magnet type motor is a brushless DC motor

Polyphase Induction Motor MCQs with Hints

76). Which one of the following is denoted by CR?
HintThe control receiver is denoted by CR, it is a type of synchro receiver
77). Which one of the following motors is not a self-starting motor?
HintThe synchronous motor is not a self-starting motor
78). The embedded magnet rotor is used in _______________
HintThe embedded magnet rotor is used in fans, pumps, irrigation, etc
79). What are the components of the motor?
HintThe rotor, bearing, stator, bracket or endplate, and lead wire are the components of motor
80). ___________________ are the type of motors classified by the principle of conversion
HintThe electromagnetic motor and ultrasonic motors are the types of motors classified by the principle of conversion
81). ______________ are the methods to control the speed of induction motors from stator side
HintThe speed of induction motors is controlled by the pole changing method, by variable frequency control, and by supply voltage control from the stator side
82). Which one of the following is denoted by CT?
HintThe control transformer is denoted by CT, it is a type of synchro transformer
83). ______________ are the methods to control the speed of induction motors from rotor side
HintThe speed of induction motors is controlled by the slip energy recovery method, by rotor resistance control, and by injection of an EMF in the rotor circuit  from the rotor side
84). The variable frequency drive has ________________ sections
HintThe variable frequency drive has converter section, inverter section, and DC bus sections
85). The variable frequency drives are used for ____________ the motor
HintThe variable frequency drives are used to stop, start, and also control the speed of the motor
86). Which one of the following has fewer energy savings?
HintThe energy-saving is less in soft starter compare to VFD
87). ___________________ are the type of motors classified by the power supply
HintThe DC power supply, single-phase, or three-phase AC power supply are the types of motors classified by the power supply
88). _____________ are the type of PM DC motors by armature type
HintThe slotted type, coreless type, and slotless type are the type of PM DC motors by armature type
89). What is the standard form of IPM?
HintThe standard form of IPM is Interior Permanent Magnet, it is a type of motor
90). The space requirement is more in _________________
HintThe space requirement is more in variable frequency drive whereas the space requirement is less in the soft starter
91). Which one of the following starters is used in medium and low torque applications?
HintThe soft starter is used in medium and low torque applications whereas the VFD used in high torque applications
92). What are the advantages of a DOL starter?
HintThe DOL starters are easy to troubleshoot, easy to understand, most economical, and cheap
93). What are the advantages of disc motor?
HintThe advantages of disc motor are low cost and smooth rotation with zero cogging
94). The disc motors are used in __________________ applications
HintThe disc motors are used in CD players, VCR players, record players, etc
95). The hysteresis motor is a type of ______________ motor
HintThe hysteresis motor is a type of synchronous motor
96). What is the standard form of SPM?
HintThe standard form of SPM is Surface Permanent Magnet, it is a type of brushless DC motor
97). What are the disadvantages of DOL starters?
HintThe DOL starter has a high starting current, high starting torque, and it is mechanically harsh
98). The direct on-line starter is suitable for _____________
HintThe direct on-line starter is suitable for conveyor belts, water pumps, and compressors
99). What are the advantages of a star-delta starter?
HintThe star-delta starter has good torque/current performance, and it is simple, cheap, and rugged
100). What are the applications of variable frequency drive?
HintThe variable frequency drive used in cane carrier drive, raw juice pumps, injection pumps, etc
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