Motor and Generator Action - Comparison

A motor and generator perform opposite functions, but their fundamental structure is the same. Their structure is a coil mounted on an axel within a magnetic field.

An electric motor is used to produce rotational motion from an electrical supply. In a motor an electric current is passed through the coil. The coil then creates a magnetic field that interacts with the already existing magnetic field. This interaction forces the coil to rotate.

⇒ For a motor the input energy is electrical energy and the useful output energy is mechanical energy.

The generator is used to produce an electric current from rotational motion (on large scale power stations a turbine is used to provide this rotation). In a generator the rotation causes the coil to rotate inside the magnetic field.* This induces an alternating current in the coil.

⇒ For a generator the input energy is mechanical energy and the useful output energy is electrical energy.

In power stations it is usually the magnet which is attached to the axel and rotated, with the coils surrounding the magnet. However the end result is the same.

The Difference Between the Motor and the Generator are explained below in the tabulated form.

BASIS	MOTOR	GENERATOR
BASISFunction	MOTORThe Motor converts Electrical energy into Mechanical Energy	GENERATORGenerator converts Mechanical energy to Electrical energy.
BASISElectricity	MOTORIt uses electricity.	GENERATORIt generates electricity
BASISDriven element	MOTORThe Shaft of the motor is driven by the magnetic force developed between armature and field.	GENERATORThe Shaft is attached to the rotor and is driven by mechanical force.
BASISCurrent	MOTORIn a motor the current is to be supplied to the armature windings.	GENERATORIn the generator current is produced in the armature windings.
BASISRule Followed	MOTORMotor follows Fleming’s Left hand rule.	GENERATORGenerator follows Fleming’s Right hand rule.
BASISExample	MOTORAn electric car or bike is an example of electric motor.	GENERATOREnergy in the form of electricity is generated at the power stations.

The motor and the generator are almost similar from the construction point of view, as both have stator and rotor. The main difference between the two is that the Motor is an electric device which converts electrical energy into mechanical energy. The generator is vice versa of that motor. It converts mechanical energy into electrical energy.

The Difference between Motor and Generator are as follows:-.

Ø  The Motor converts electric energy into mechanical energy, whereas generator does the opposite.

Ø  Electricity is used in the motor, but the generator produces the electricity.

Ø  The Shaft of the motor is driven by the magnetic force developed between armature and field windings whereas, in the case of the Generator the Shaft is attached to the rotor and is driven by mechanical force.

Ø  The current is to be supplied to the armature windings in case of a Motor, and in Generator, current is produced in the armature windings.

Ø  Motor follows Fleming’s Left hand rule while Generator follows Fleming’s Right hand rule.

Ø  The example of Motor is an electric car or bike where electric current is supplied to the machine or device, and it gets converted into mechanical motion and, as a result, the car or bike moves. The example of Generator is that in power stations the turbine is used as a device which converts mechanical energy of force of water falling from the dam to generate electric energy.

MCQ

1.    No-load speed of which of the following motor will be highest ?
(a)     Shunt motor     
(b)     Series motor
(c)    Cumulative compound motor
(d)    Differentiate compound motor
Ans: b
2.    The direction of rotation of a D.C. series motor can be changed by 
(a)     interchanging supply terminals 
(b)     interchanging field terminals
(c)    either of (a) and (b) above
(d)    None of the above
Ans: b

3. Which of the following application requires high starting torque ? 
(a) Lathe machine
(b) Centrifugal pump
(c) Locomotive
(d) Air blower
Ans: c

4.    If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?
(a)     Series motor
(b)     Shunt motor
(c)    Differentially compound motor
(d)    Cumulative compound motor
Ans: a

5.    Which D.C. motor will be preferred for machine tools ?
(a)    Series motor
(b)    Shunt motor    
(c)    Cumulative compound motor
(d)    Differential compound motor
Ans: b

6.    Differentially compound D.C. motors can find applications requiring
(a)    high starting torque
(b)    low starting torque 
(c)     variable speed
(d)    frequent on-off cycles
Ans: b

7.    Which D.C. motor is preferred for elevators ?
(a)    Shunt motor
(b)    Series motor
(c)    Differential compound motor
(d)    Cumulative compound motor
Ans: d

8.    According to Fleming's left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
(a)     current in the conductor aovtaat of conductor
(c)    resultant force on conductor
(d)    none of the above
Ans: a

9.    If the field of a D.C. shunt motor gets opened while motor is running
(a) the speed of motor will be reduced %
(b) the armature current will reduce 
(c)  the motor will attain dangerously high speed 1      
(d) the motor will continue to nuvat constant speed
Ans: c

10.    Starters are used with D.C. motors because
(a)    these motors have high starting torque
(b)    these motors are not self-starting
(c)    back e.m.f. of these motors is zero initially
(d)    to restrict armature current as there is no back e.m.f. while starting
Ans: d

Share on Google Plus

About Unknown