Question 1a
Using the equivalent circuit of a separately excited DC motor, illustrate what affects the speed of such a motor.
(10 marks)
Question 1b
A 28 V separately excited motor has the following specifications:
Armature resistance = 0.5 ohms
Voltage constant = 0.7 V/rad/s,
Torque constant = 100 Nm/s
Field current = 10 mA

Question 1b(i)
Calculate the speed when the developed torque is 10 Nm.
(4 marks)
Question 1b(ii)
Demonstrate how the torque of the motor can be increased without reducing the speed. (5 marks)
Question 1c
Infer from the results you have obtained from Q1a, explain how speed control can be achieved in a permanent magnet brushed DC motor.
(2 marks)
Question 1d
Compare the advantages and disadvantages of using brushless DC permanent magnet motors with using permanent magnet brush DC motor in drones.
(4 marks)