Before analysing the various characteristics of motors, let us revise the torque and speed equations are applied to various types of motors.

**.**T α Φ I

^{.}._{a }from torque equation.

This is because, 0.159(PZ)/A is a constant for a given motor.

Now Φ is the flux produced by the field winding and is proportional to the current passing through the field winding.

Φ α I

Φ α I

_{field }
But for various types of motors, current through the field winding is different. Accordingly torque equation must be modified.

For a d.c. shunt motor, I

_{sh }is constant as long as supply voltage is constant. Hence Φ flux is also constant.**.**T α Ia for shunt motors

^{.}.
For a d.c. series motor, I

_{se }is same as I_{a}. Hence flux Φ is proportional to the armature current I_{a}.**.**T α I

^{.}._{a }α I

_{a}

^{2}

_{ }for series motors.

Similarly as E

_{b }^{ }= (ΦPNZ)(60A), we can write the speed equation as,
E

_{b }α^{ }Φ N**.**N α E

^{.}._{b}/Φ

But V = E

_{b }+ I_{a }R_{a }neglecting brush drop**.**E

^{.}._{b }= V - I

_{a }R

_{a}

**.**Speed equation becomes,

^{.}.
N α (V-I

_{a }R_{a})/Φ
So for shunt motor as flux is constant,

**.**N α V - I

^{.}._{a }R

_{a}

These relations play an important role in understanding the various characteristics of different types of motors.

__1.1 Speed Regulation__

The speed regulation for a d.c. motor is defined as the ratio of change in speed corresponding to no load and full load condition to speed corresponding to full load.

Mathematically it is expressed as,

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Thanks for sharing your thoughts. I truly appreciate your efforts and I am waiting for your next write ups thanks once again.

ReplyDeletePauleen

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