Description
A 550 V, 8 pole dc Series motor has the following name plate details:
RATING 150 kW
VOLTAGE 550 V dc
POLES 8
CURRENT 305 A
SPEED 450 rev/min
CONNECTION SERIES
The motor parameters are:
Armature Resistance RA = 0.07 Ω
Armature Conductors 1112
Armature Winding Type: Lap
Series Field Resistance RS = 0.04 Ω
The series dc motor above is supplied from a 550 V source via a step down DC/DC chopper converter which has a switching period of 5 ms.
Given that the armature voltage constant for the motor is K = 0.03593 V/A-rad/s.
(i) Draw a diagram of the system showing converter and dc motor. [5 Marks]
Determine:
(ii) The average DC voltage applied to the motor if the switch ON time of the converter is 3.5 ms. [7 Marks]
(iii) The internal generated voltage (back emf) of the motor if it draws a constant current of 250 A from the supply. [7 Marks]
(iv) The operating speed of the motor in rev/min when drawing 250 A.[13 Marks]
(v) The induced (developed) torque in Newton metres of the motor. [11 Marks]
(vi) The useful flux per pole in milli webers (mWb) of the motor for input current of 250 A. [7 Marks]
Assume linear magnetic characteristics for the dc motor
Explanation & Answer
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