How to control the speed of induction motors? Do variable frequency drives plays a role in that?

How to control the speed of induction motors? Do variable frequency drives plays a role in that?
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VSD - DC/DC usage to drive compressors allows controlling and accurate measurements on speed and torque of compressor motors, and so enhancing its application characteristics. Integrating of VSD - DC/DC systems in compressors have significant technical and economical advantages including significant energy savings, and consequently the related reductions in CO emissions, are possible through usages of these drives in a wide variety of applications in industry. In addition, in order to omit the energy losses in DC compressors, a new zero current transition PWM forward converter is introduced, which applies a basic but vital auxiliary circuit. The converter is analyzed; design and considerations have been discussed.
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The variable resistance placed in the rotor circuit of a wound-rotor induction motor provides for __________. A. speed control B. frequency control C. voltage control D. use as a split-phase motor

Description : The variable resistance placed in the rotor circuit of a wound-rotor induction motor provides for __________. A. speed control B. frequency control C. voltage control D. use as a split-phase motor

Last Answer : Answer: A

The speed of a three-phase induction motor is controlled by variable voltage variable frequency control

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Last Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases 

Which of the following in an application of D.C. motors? (a) Traction (b) Drives for process industry (c) Battery driven vehicles (d) Automatic control (e) All of the above

Description : Which of the following in an application of D.C. motors? (a) Traction (b) Drives for process industry (c) Battery driven vehicles (d) Automatic control (e) All of the above

Last Answer : (e) All of the above

In a variable speed induction motor derive V/f kept constant over a wide range of its frequency variation. ...

Description :  In a variable speed induction motor derive V/f kept constant over a wide range of its frequency variation. The motor operates in the following mode : -  a) Constant power mode b) Constant torque mode c) Constant slip mode d) Variable power and variable torque mode

Last Answer :  In a variable speed induction motor derive V/f kept constant over a wide range of its frequency variation. The motor operates in the following mode : - Constant torque mode

State two benefits and applications of variable frequency drives.

Description : State two benefits and applications of variable frequency drives. 

Last Answer : Benefits and applications of variable frequency drives: The variable frequency drive helps to conserve electrical energy and gives the following benefits: 1) Energy saving due to optimum use for applications ... 4) Process control drives. 5) Textile industry machines. 6) Paper industry machines. 

Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under no load. C. A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.

Description : Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under ... A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.

Last Answer : Answer: A

Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical appliances made of silicon steel contains maximum percentage of silicon (about 4%)? (A) Armature of small motors/generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers

Description : Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical ... /generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers

Last Answer : (D) High frequency transformers

The speed and torque of induction motors can be varied by which of the following means:

Description : The speed and torque of induction motors can be varied by which of the following means: 1) Stator voltage control 2) Rotor voltage control 3) Frequency control 4) All of these

Last Answer : All can off them can control speed and torque of induction motor.This is because  increased supply frequency increases synchronous speed  which will definetly affect torque and speed . .Both stator and rotor  voltage control are proportional to torque and slip.

The following function plays an important role in the experimental modal analysis: a. time-response function b. modal-response function c. frequency-response function

Description : The following function plays an important role in the experimental modal analysis: a. time-response function b. modal-response function c. frequency-response function

Last Answer : c. frequency-response function

What are the factors to be considered while selection of motors for different drives?

Description : What are the factors to be considered while selection of motors for different drives?

Last Answer : Following Factors are considered while selecting electric drive (Motor) for particular application:  Factors to be considered for selection of Electrical Drives:  1) Nature of Supply:- Whether supply ... , load equalization 7) Cost: - Capital, Running and maintenance cost should be less.  

Which part of the brain plays an important role in motor control? (1) Cerebellum (2) Cerebrum (3) Medulla (4) Pons

Description : Which part of the brain plays an important role in motor control? (1) Cerebellum (2) Cerebrum (3) Medulla (4) Pons

Last Answer : (1) Cerebellum Explanation: The cerebellum, also known as little brain, is a region of the brain that plays an important role in balance and motor control. It is also involved in some ... functions (such as regulating fear and plea-sure responses) and in the processing of procedural memories.

Point out the wrong statement. a) In theory, any application can run either completely or partially in the cloud b) The location of an application or service plays a fundamental role in how the application must be written c) An application or process that runs on a desktop or server is executed coherently, as a unit, under the control of an integrated program CSE-R17.BLOGSPOT.COM d) None of the mentioned

Description : Point out the wrong statement. a) In theory, any application can run either completely or partially in the cloud b) The location of an application or service plays a fundamental role in how the ... unit, under the control of an integrated program CSE-R17.BLOGSPOT.COM d) None of the mentioned

Last Answer : None of the mentioned

Which bus plays a crucial role in I/O: a. System bus b. Control bus c. Address bus d. Both A and B

Description : Which bus plays a crucial role in I/O: a. System bus b. Control bus c. Address bus d. Both A and B

Last Answer : b. Control bus

Which part of the brain plays an important role in motor control? (1) Cerebellum (2) Cerebrum (3) Medulla (4) Pons

Description : Which part of the brain plays an important role in motor control? (1) Cerebellum (2) Cerebrum (3) Medulla (4) Pons

Last Answer : Cerebellum

By which of the following methods motor rating for variable load drives can be determined ? (a) Method of average losses (b) Equivalent current method (c) Equivalent torque method (d) Equivalent power method (e) All of the above.

Description : By which of the following methods motor rating for variable load drives can be determined ? (a) Method of average losses (b) Equivalent current method (c) Equivalent torque method (d) Equivalent power method (e) All of the above.

Last Answer : (e) All of the above.

The air gap provided in induction motors should be checked periodically with a feeler gage to detect an unequal air gap and _____________. A. decreased motor magnetizing current B. hysteresis loses C. increased power factor D. mechanical damage to the rotor

Description : The air gap provided in induction motors should be checked periodically with a feeler gage to detect an unequal air gap and _____________. A. decreased motor magnetizing current B. hysteresis loses C. increased power factor D. mechanical damage to the rotor

Last Answer : Answer: D

Most three-phase induction motors of five horsepower or less, are started by _____________. A. autotransformer starters B. resistor starters C. across-the-line starters D. reactor starters

Description : Most three-phase induction motors of five horsepower or less, are started by _____________. A. autotransformer starters B. resistor starters C. across-the-line starters D. reactor starters

Last Answer : Answer: C

Most three-phase induction motors used for driving engine room auxiliaries are started by _____________. A. resistor starters B. across-the-line starters C. impedance starters D. reactor starters

Description : Most three-phase induction motors used for driving engine room auxiliaries are started by _____________. A. resistor starters B. across-the-line starters C. impedance starters D. reactor starters

Last Answer : Answer: B

Which of the following types of motors is often designed for use in correcting power factor? A. Polyphase B. Wound-rotor C. Induction D. Synchronous

Description : Which of the following types of motors is often designed for use in correcting power factor? A. Polyphase B. Wound-rotor C. Induction D. Synchronous

Last Answer : Answer: D

Autotransformer starters or compensators are sometimes used with polyphase induction motors to _____________. A. reduce the voltage applied to the motor during the starting period B. increase the voltage for 'across-the-line starting' C. provide a backup means of voltage regulation for emergency starting D. allow the voltage to be either stepped up or down, depending on the application, to ensure full torque

Description : Autotransformer starters or compensators are sometimes used with polyphase induction motors to _____________. A. reduce the voltage applied to the motor during the starting period B. increase the voltage for ' ... to be either stepped up or down, depending on the application, to ensure full torque

Last Answer : Answer: A

In general, polyphase induction motors can be started on full line voltage by means of ______________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters

Description : In general, polyphase induction motors can be started on full line voltage by means of ______________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters

Last Answer : Answer: C

Low horsepower, polyphase, induction motors can be started with full voltage by means of _____________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters

Description : Low horsepower, polyphase, induction motors can be started with full voltage by means of _____________. A. compensator starters B. autotransformer starters C. across-the-line starters D. primary-resistor starters

Last Answer : Answer: C

Why Induction motors are widely used in Industries?

Description : Why Induction motors are widely used in Industries?

Last Answer : Answer: In Industries 80% of the motor drives used are induction motors. Induction Motors are widely used in Industries because of some features it possess. They are: • Low Cost • Simple and Rugged Construction • Absence of Commutator • Good power factor • Higher efficiency • Good Speed Regulation

Slip ring induction motor advantages and disadvantages compared to squirrel cage motors?

Description : Slip ring induction motor advantages and disadvantages compared to squirrel cage motors?

Last Answer : Advantages: High starting torque with low starting current Smooth acceleration under heavy loads No abnormal heating during starting Good running characteristics after external rotor resistances are cut out ... cage motors The speed regulation is poor when run with resistance in the rotor circuit

What are the advantages and disadvantages of Induction Motors?

Description : What are the advantages and disadvantages of Induction Motors?

Last Answer : Advantages: It is simple and rugged in construction It is relatively cheap Induction motors require less maintenance Induction motor has high efficiency and reasonably good power factor 3-phase induction ... and its speed cannot be changed easily Its starting torque is inferior to dc shunt motor

Why do we use capacitor-start induction motors in applications requiring high starting torque in preference to repulsion induction motors?

Description : Why do we use capacitor-start induction motors in applications requiring high starting torque in preference to repulsion induction motors?

Last Answer : Capacitors are easily available, cheaper and reliable. Repulsion-induction motors posses a special commutator and brushes that require maintenance. Most manufacturers have stopped making them.

Why capacitor –start induction motors advantageous?

Description : Why capacitor –start induction motors advantageous?

Last Answer : In capacitor start induction motors capacitor is connected in series with the auxiliary winding. When speed of the motor approaches to 75 to 80% of the synchronous speed the starting winding gets ... torque is proportional to phase angle ά and hence such motors produce very high starting torque.

Give applications of Capacitor start Induction run motors.

Description : Give applications of Capacitor start Induction run motors.

Last Answer : Drilling machine, centrifugal pump, grinders , refrigerator etc

Why do we use capacitor-start induction motors in applications requiring high starting torque in preference to repulsion induction motors?

Description : Why do we use capacitor-start induction motors in applications requiring high starting torque in preference to repulsion induction motors?

Last Answer : Ans : Capacitors are easily available, cheaper and reliable. Repulsion-induction motors posses a special commutator and brushes that require maintenance. Most manufacturers have stopped making them.

Why are centrifugal switches provided on many 1-phase Induction motors?

Description : Why are centrifugal switches provided on many 1-phase Induction motors?

Last Answer : Centrifugal switches are provided on many 1-phase Induction motors to disconnect the starting / auxiliary winding from the supply when the motor reaches about 70% of its synchronous speed.

Name types of 1-phase induction motors.

Description : Name types of 1-phase induction motors.

Last Answer : Based on the method of starting arrangement provided, the 1-phase Induction motors are classified as follows (i) Split-phase motor (ii) Shaded pole motor (iii) Resistor start Induction run ... iv) capacitor start Induction run single phase IM (v) capacitor start Capacitor run single phase IM

Name the two different theories with which principle of 1-phase induction motors are explained

Description : Name the two different theories with which principle of 1-phase induction motors are explained

Last Answer : The two different theories are · Double revolving field theory · Cross field theory

Where do we require single-phase induction motors?

Description : Where do we require single-phase induction motors?

Last Answer : Single-phase induction motors are required where (i) 3 phase supply is not available (ii) Efficiency is of lesser importance (iii) Rating is less than one H.P. (iv) Equipment is portable

On which Following products is labelling not Voluntary a) Colour TV c) Ceiling fans b) Ballast d) Induction motors

Description : On which Following products is labelling not Voluntary a) Colour TV c) Ceiling fans b) Ballast d) Induction motors

Last Answer : Colour TV

Products on which labeling is voluntary are a) Electric geysers b) Induction motors b) Ceiling fans d) All of the above

Description : Products on which labeling is voluntary are a) Electric geysers b) Induction motors b) Ceiling fans d) All of the above

Last Answer : All of the above

How do split-phase induction motors become self-starting?

Description : How do split-phase induction motors become self-starting?

Last Answer : By using combinations of inductance and capacitance to apply out-of phase currents in starting windings.

In induction motors, the length of air gap in kept as small as mechanically possible is order to have (a) low power factor (b) high power factor (c) high over load capacity (d) any of the above

Description : In induction motors, the length of air gap in kept as small as mechanically possible is order to have (a) low power factor (b) high power factor (c) high over load capacity (d) any of the above

Last Answer : (b) high power factor

SINGLE PHASE INDUCTION MOTORS MCQ

Description : SINGLE PHASE INDUCTION MOTORS MCQ

Last Answer : 101. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on (a) running winding (b) rotor winding (c) field winding (d) compensating winding Ans: a ... motor is usually reduced by using (a) gearing (b) belts (c) brakes (d) chains Ans: a

THREE PHASE INDUCTION MOTORS MCQ

Description : THREE PHASE INDUCTION MOTORS MCQ

Last Answer : 101. Insertion of resistance in the stator of an induction motor (a) increases the load torque (b) decreases the starting torque (c) increases the starting torque (d) none of the above Ans: b

State the types of single phase induction motors.

Description : State the types of single phase induction motors.

Last Answer : The types of single phase induction motors are: i) Resistance split phase induction motor. ii) Capacitor split phase inductor motor. a. Capacitor start induction run motor b. permanent capacitor motor c. capacitor start capacitor run induction motor iii) Shaded pole induction motor.

What is the effect of following on induction motors: (1) Voltage unbalance (2) Harmonic distortion

Description : What is the effect of following on induction motors: (1) Voltage unbalance (2) Harmonic distortion

Last Answer : i) Effect of voltage unbalance: For three phase motors this leads to unequal currents in the three phase windings that result in unbalance in the fields produced due to which negative phase ... currents thereon). This leads to motor failures, lower life and improper torque speed characteristics. 

State the classification of single phase induction motors.

Description : State the classification of single phase induction motors.

Last Answer : Types of single phase induction motors: 1. Split phase induction motor. 2. Capacitor start inductor motor. 3. Capacitor start capacitor run induction motor. 4. Permanent split capacitor motor. 5. Shaded pole induction motor. 

Deep bar rotor construction is used in three phase induction motors to mainly:

Description : Deep bar rotor construction is used in three phase induction motors to mainly: (1) Control speed (2) Control power factor (3) Increase starting torque (4) None of these

Last Answer : Deep bar rotor construction is used in three phase induction motors to mainly: Increase starting torque

In the Squirrel cage induction motors, the rotor slots are usually a slight skew to reduce

Description : In the Squirrel cage induction motors, the rotor slots are usually a slight skew to reduce (A) Windage losses (B) Eddy currents (C) Accumulation of dirt and dust (D) Magnetic hum

Last Answer : Eddy   currents.

Slot harmonics are reduced in induction motors by using

Description : Slot harmonics are reduced in induction motors by using (A) fractional-pitch windings (B) fractional-slot windings (C) integral-slot windings (D) distributed windings

Last Answer : Slot harmonics are reduced in induction motors by using fractional-slot windings

Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as

Description : Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as (A) One-third of their synchronous speed (B) One-fifth of their synchronous speed (C) One-seventh of their synchronous speed (D) One-ninth of their synchronous speed

Last Answer : Generally, Crawling in squirrel cage induction motors is tendency to run stably at speeds as low as One-seventh of their synchronous speed

Shunt, series, and compound wound motors, are all DC motors designed to operate from _____________. A. constant potential, variable current DC sources B. variable potential, constant current DC sources C. variable potential, variable current DC sources D. constant potential, constant current DC sources

Description : Shunt, series, and compound wound motors, are all DC motors designed to operate from _____________. A. constant potential, variable current DC sources B. variable potential, constant current DC ... C. variable potential, variable current DC sources D. constant potential, constant current DC sources

Last Answer : Answer: A

Vauxhall Motors is producing a new van with four-wheel drive Which one of the following would be a likely variable for segmenting the market for this new model? A)Religion B)Geographic location C)Income D)Political views

Description : Vauxhall Motors is producing a new van with four-wheel drive Which one of the following would be a likely variable for segmenting the market for this new model? A)Religion B)Geographic location C)Income D)Political views

Last Answer : B)Geographic location

Compare variable reluctance and permanent magnet motors.

Description : Compare variable reluctance and permanent magnet motors.

Last Answer : Variable reluctance Motor  Permanent magnet motors   The rotor is not magnetised The rotor is magnetised  High torque to inertia ratio  Low torque to inertia ratio  ... rotor has salient pole construction The rotor has mostly smooth cylindrical type of construction. 

How do I connect 180 DC motors to LiPo batteries and how to control their speed?

Description : How do I connect 180 DC motors to LiPo batteries and how to control their speed?

Last Answer : A brushless DC electric motor ( BLDC motor or BL motor), also known as electronically commutated motor (ECM or EC motor) and synchronous DC motors , are synchronous motors powered by direct current ... provides pulses of current to the motor windings that control the speed and torque of the motor.