Sign Up

Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.

Sign In

Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.

Forgot Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

You must login to ask question.

Please briefly explain why you feel this question should be reported.

Please briefly explain why you feel this answer should be reported.

Please briefly explain why you feel this user should be reported.

Electrical Drive MCQs

Electrical Drive MCQs

An electrical drive is a device that is used to control the output of the motor. Electrical drives form an integral part of industrial automation and control processes where precise motor speed control is desired. Modern-day locomotives are also powered by electrical drives. At the beginning of the era of electrical machines, it was thought that the speed of the generator and motor can be only controlled by varying applied voltage and frequency. However, the invention of drives totally brought a revolution in motor controls. Generally, a motor drive comprises power electronics, motor, sensor, and controller. Given below are the top 10 MCQs on Electrical drives.

An electric drive is best defined as a device that

An electric drive is best defined as a device that:

  1. Electrical energy into kinetic energy
  2. Kinetic energy into electrical energy
  3. Mechanical energy into electrical energy
  4. Electrical energy into mechanical energy

Correct answer: 4. Electrical energy into mechanical energy

Explanation: The electrical drive converts electrical energy into mechanical energy while providing a precise control over the process.

The choice of electric drive for a particular application depends on

The choice of electric drive for a particular application depends on

  1. Environmental condition
  2. Speed control range
  3. Starting Nature
  4. All of the above

Correct answer: 4. All of the above

Explanation:

The choice of a particular drive depends on multiple factors. Some of these include:

  • Motor efficiency
  • Braking requirement
  • Starting requirements
  • Limits of speed range
  • Power factor
  • Reliability
  • Load factor
  • Variation in input supply
  • Environmental aspects
  • Economical aspects

From given list, methods of electrical braking are

From given list, methods of electrical braking are:

  1. Dynamic
  2. Plugging
  3. Regenerative
  4. All of these

Correct answer: 4. All of these

Explanation: The term braking refers to method of stopping the motor intentionally. The mechanical braking method is the basic braking. It involves noise, temperature rise, maintenance and repair. In order to reduce the effects of mechanical braking, electrical braking is used.

Of all above mentioned methods, all three methods are all the different types of electrical braking methods. On its own, the electric braking is ineffective for stopping the motor effectively. Electrical braking is therefore accompanied with mechanical braking which makes the overall braking system more effective.

VVVF in Electrical Engineering stands for

VVVF in Electrical Engineering stands for

  1. Variable voltage var frequency
  2. Var variable voltage frequency
  3. Variable voltage variable force
  4. Variable voltage variable frequency

Correct answer: 1. Variable voltage variable frequency

Explanation: VVVF stands for variable voltage variable frequency control.

Variable Voltage Variable Frequency (VVVF) drives employ frequency inverter technology that regulates both input voltage and frequency and draws much less current during acceleration and deceleration process.

The basic elements of electric drive are

The basic elements of electric drive are

  1. Electric motor
  2. Control system
  3. Both of these
  4. None of these

Correct answer: 3. Both of these

Explanation: An electrical drive is combination of electric motor and control system that is designed to control certain parameters of the motor for converting electrical energy into mechanical power in a precise controllable way.

The speed control method that is preferred for constant torque drive

The speed control method that is preferred for constant torque drive:

  1. Armature voltage control
  2. Field control
  3. Mechanical loading system
  4. None of above

Correct answer: 1. Armature voltage control

Explanation: By controlling armature voltage, the speeds up to the rated speed can be achieved. Speeds beyond rated speed are never achieved using armature voltage control. In order to achieve this, field current is reduced. Reduction of field flux has outcomes that it has less produced torque while keeping power the same. Henceforth the field control is termed as constant power control. Reduction in armature flux tends to produce less power. However torque remains same. Henceforth, the armature voltage control is known as constant torque control.

Group drive is also known as

Group drive is also known as

  1. Individual drive
  2. Line shaft drive
  3. Multimotor drive
  4. None of these

Correct answer: 2. Line shaft drive

In 4 quadrant operation of a hoist the 3rd quadrant implies

In 4 quadrant operation of a hoist the 3rd quadrant implies:

  1. Forward braking
  2. Forward motoring
  3. Reverse motoring
  4. Reverse braking

Correct answer: 3. Reverse motoring

  • Quadrant 1 : Forward braking
  • Quadrant 2 : Forward motoring
  • Quadrant 3 : Reverse motoring
  • Quadrant 4 : Reverse braking

AC motor while operating on variable frequency supply requires variable voltage in order to

AC motor while operating on variable frequency supply requires variable voltage in order to

  1. Avoid effect of saturation
  2. Shield the insulation
  3. Improve the capabilities of the inverter
  4. Protect thyristor from dv/dt

Correct answer: 1. Avoid effect of saturation

Explanation:

Whenever frequency is changed, the induction motor characteristics require the applied voltage to be proportionally adjusted. As an example, if a motor is designed to operate at 440 Volts at 50 Hz, the applied voltage must be reduced to 230 Volts when the frequency is reduced to 25 Hz.

The ratio of volts per hertz must be regulated to keep up to a constant value (440/50 = 8.8 in this case).

If such condition is not achieved, then due to the saturation in the core, the machine can get the magnetized soon if we continued to run the motor, the motor can be damaged.

An elevator drive is required to operate in

An elevator drive is required to operate in

  1. One quadrant only
  2. Two quadrants
  3. Three quadrants
  4. Four quadrants

Correct answer: 4. Four quadrants

Explanation: Elevator drives operate in four quadrants. These four quadrants are:

  • Forward motoring (1st quadrant)
  • Forward braking (2nd quadrant)
  • Reverse motoring (3rd quadrant)
  • Reverse braking (4th quadrant)

Related Posts

Leave a comment