LOSSES IN DC MACHINE

yashyash

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Construction of DC Machines Construction of DC Machines

Commutator

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Features of DC Machine Features of DC Machine

Field Winding

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DC Machines- DC Machines- Direction of Power Flow and Losses Direction of Power Flow and Losses

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DC Machines- DC Machines- Direction of Power Flow and Losses Direction of Power Flow and Losses

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DC Machines AnalysisDC Machines AnalysisSymbols that will be used.

= flux per pole p = no. of poles z = total number of active conductors on the armature a = no. of parallel paths in the armature winding

          Aside: Lap Winding -> a = p                 Wave Winding -> a = 2

n = speed of rotation of the armature in rpmwm = speed in radians per second

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DC Machines ConnectionsDC Machines Connections

E

-

+Field

F F

Armature

b) Separately Excited

E

RaIf +

--

+VT

a)

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DC Machines ConnectionsDC Machines Connections

E

-

+

Field

F F

Armature

c) Series

E

-

+

Field

F F

Armature

d) Shunt

A

A

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DC Machines ConnectionsDC Machines Connections

E

-

+

Field FF

Arm aturee) Cummulative Com pound

A

A

S S

E

-

+

Field FF

Armatured) Differential Compound

A

A

S S

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DC Machines ConnectionsDC Machines Connections

E

-

+

Field FF

Arm atureg) Short Shunt

A

A

S S

E

-

+

Field FF

Armaturef) Long Shunt

A

A

S S

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TORQUE EQUATIONTORQUE EQUATION

EaIa=Tem - In the DC machine losses areexpressed as rotational losses due to friction and windage (F&W).

- The torque equation can then be rewritten as:-

  SHAFT OUTPUT TORQUE = (Te - TF&W)

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