3. (i) (ii) (iii) A series DC motor runs at 800 rpm when the voltage is 400 V and the current is 25 A. The armature resistance is 0.4 0 and the series field resistance is 0.2 0. Determine the back-emf of the motor. The speed of the motor is to be reduced to 600 rpm by inserting a resistance in series with the armature. Determine the new back-emf of the motor. Determine the value of the resistance to be added. What is the main disadvantage of controlling the speed by adding a series resistance?
3. (i) (ii) (iii) A series DC motor runs at 800 rpm when the voltage is 400 V and the current is 25 A. The armature resistance is 0.4 0 and the series field resistance is 0.2 0. Determine the back-emf of the motor. The speed of the motor is to be reduced to 600 rpm by inserting a resistance in series with the armature. Determine the new back-emf of the motor. Determine the value of the resistance to be added. What is the main disadvantage of controlling the speed by adding a series resistance?
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Transcribed Image Text:3.
(i)
(ii)
(iii)
A series DC motor runs at 800 rpm when the voltage is 400
V and the current is 25 A. The armature resistance is 0.4 0
and the series field resistance is 0.2 0.
Determine the back-emf of the motor.
The speed of the motor is to be reduced to 600 rpm by
inserting a resistance in series with the armature.
Determine the new back-emf of the motor.
Determine the value of the resistance to be added. What is
the main disadvantage of controlling the speed by adding a
series resistance?
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