Compensating Windings MCQ Quiz - Objective Question with Answer for Compensating Windings - Download Free PDF

Explanation:

The application of DC Motors are as follows:

DC shunt motor

• Shunt DC motors are utilized in Centrifugal Pumps, Lifts, Weaving Machines, Lathe Machines, Blowers, Fans, Conveyors, Spinning Machines, and other applications where a consistent speed is required.
   

DC series motor 

• DC series motors are used where high starting torque is required. Major applications for DC motors are elevators, steel mills, rolling mills, locomotives, and excavators.
   

Cumulative compound DC motor

• It has high starting torque and has varying speeds within limits i.e. it has self-adjustable speed with changing load. These are used where we require sudden heavy loads for a short duration.​
• Hence, it is used for driving constant speed line shafts, lathes, constant speed head centrifugal pumps, fans woodworking machines, reciprocating pumps, etc.
   

Differentially compound DC motor

• The differential compound generators are used for arc welding purposes where a large voltage drop and constant current are required.

The correct answer is 'option 3'

Concept:

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience a sudden shift in the magnetic neutral axis.
• This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces.
• It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate for the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience the sudden shift in magnetic neutral axis. This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces. It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience the sudden shift in magnetic neutral axis. This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces. It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

The correct answer is 'option 3'

Concept:

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience a sudden shift in the magnetic neutral axis.
• This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces.
• It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate for the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

Explanation:

The application of DC Motors are as follows:

DC shunt motor

• Shunt DC motors are utilized in Centrifugal Pumps, Lifts, Weaving Machines, Lathe Machines, Blowers, Fans, Conveyors, Spinning Machines, and other applications where a consistent speed is required.
   

DC series motor 

• DC series motors are used where high starting torque is required. Major applications for DC motors are elevators, steel mills, rolling mills, locomotives, and excavators.
   

Cumulative compound DC motor

• It has high starting torque and has varying speeds within limits i.e. it has self-adjustable speed with changing load. These are used where we require sudden heavy loads for a short duration.​
• Hence, it is used for driving constant speed line shafts, lathes, constant speed head centrifugal pumps, fans woodworking machines, reciprocating pumps, etc.
   

Differentially compound DC motor

• The differential compound generators are used for arc welding purposes where a large voltage drop and constant current are required.

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience the sudden shift in magnetic neutral axis. This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces. It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

The correct answer is 'option 3'

Concept:

• Compensating winding are used in DC machines to neutralize the cross magnetizing effect of armature reaction.
• Cross magnetizing effect changes with load current and it results in shifting of the magnetic neutral axis.
• The machines which are subjected to large changes in load will experience a sudden shift in the magnetic neutral axis.
• This will result in a statically induced emf in the armature of the DC machine.
• This statically induced emf in armature may strike an arc between the commutator segments and result in flash-over in the whole commutator segments.
• Compensating winding is also known as pole face winding.
• Compensating winding is embedded in the slots in pole faces.
• It is connected in series with the armature winding so that their mmfs are proportional to the same current.
• To compensate for the effect of armature reaction, the direction of current in compensating winding must be opposite to that in the armature winding just below the pole face.
• Compensating winding are generally used only large machines which are subjected to large fluctuations due to their large size and increased cost.

Total mmf required at rated load

= 3 × 1000 = 3000 AT

Total mmf required at no load

= 2 × 1000 = 2000 AT

The mmf to be supplied by series field winding

= 3000 – 2000 = 1000 AT

The line current at full load,

\({I_L} = \frac{{10 \times {{10}^3}}}{{230}} = 43.48\;A\)

Armature current = 43.48 + 2 = 45.48 A

Required series filed turns per pole

\(= \frac{{1000}}{{45.48}} = 21.98\) turns per pole.

Explanation:

The application of DC Motors are as follows:

DC shunt motor

• Shunt DC motors are utilized in Centrifugal Pumps, Lifts, Weaving Machines, Lathe Machines, Blowers, Fans, Conveyors, Spinning Machines, and other applications where a consistent speed is required.
   

DC series motor 

• DC series motors are used where high starting torque is required. Major applications for DC motors are elevators, steel mills, rolling mills, locomotives, and excavators.
   

Cumulative compound DC motor

• It has high starting torque and has varying speeds within limits i.e. it has self-adjustable speed with changing load. These are used where we require sudden heavy loads for a short duration.​
• Hence, it is used for driving constant speed line shafts, lathes, constant speed head centrifugal pumps, fans woodworking machines, reciprocating pumps, etc.
   

Differentially compound DC motor

• The differential compound generators are used for arc welding purposes where a large voltage drop and constant current are required.

Compensating Winding

• Compensating winding is used in DC machines to neutralize the cross-magnetizing effect of the armature reaction.
• All armature conductors placed under the main poles region produce e.m.f which is at a right angle (90°) to the main field e.m.f. This e.m.f causes distortion in the main field flux. This is known as the cross-magnetizing effect.
• To minimize the cross-magnetizing effect compensating winding is used. This compensating winding produces an m.m.f which opposes the m.m.f produced by armature conductors.
• This is achieved by connecting compensating winding in series with armature winding. In absence of compensating winding, the cross-magnetizing effect causes sparking at the commutators and short-circuits the whole armature winding.

Additional Information Interpoles in DC machines

• Compensating winding is used to neutralize the armature reaction in the d-axis only but not in the interpolar region. To reduce armature reaction in interpolar region, interpoles are used.
• These interpoles are small in size and placed in between the main poles of the yoke.
• Like compensating winding, interpoles are also connected in series with armature winding such that the m.m.f produced by them opposes the m.m.f produced by the armature conductor in the interpolar region.
• In generators, the Interpol polarity is the same as that of the main pole ahead such that they induce an e.m.f which is known as commutating or reversing e.m.f. This commutating e.m.f minimizes the reactance e.m.f and hence sparks or arcs are eliminated.
• Compensating winding and interpoles are used for the same purpose but the difference between them is, interpoles produce e.m.f for neutralizing reactance e.m.f whereas compensating winding produces an m.m.f which opposes the m.m.f produced by conductors.

Compensating winding ampere turns

\(= \frac{{{Z_{cw}}}}{2} \cdot {I_a}\)

\(= \frac{{Pole\;Ar{c_{}}}}{{Pole\;pitch}} \times \frac{Z}{2}\frac{{{I_a}}}{{A{P_{}}}}\)

\({Z_{cw}} = \frac{{Pole\;arc}}{{Pole\;pitch}} \times \frac{Z}{{PA}}\)

\(= \frac{{0.75 \times 1600}}{{8 \times 8}}\)

Compensating winding mmf per pole (AT_C)  

\(A{T_C} = \frac{{pole\ arc}}{{pole\ pitch}} \times \frac{Z}{{2P}} \times \frac{{{I_a}}}{A} = \frac{{{Z_{cw}} \cdot {J_a}}}{2}\) 

⇒ Compensating winding conductor, \({Z_{cw}} = \frac{{pole\ are}}{{pole\ pitch}} \times \frac{Z}{{PA}}\)

\(= 0.8 \times \frac{{750}}{{15 \times 15}}\)