(Solved): estion 4 (a) A 750-V DC shunt motor has an armature resistance of \( 0.15 \Omega \) and a shunt fi ...

estion 4 (a) A 750-V DC shunt motor has an armature resistance of \( 0.15 \Omega \) and a shunt field winding resistance of \( 55 \Omega \). The motor operates at a speed of \( 1000 \mathrm{rpm} \) when the armature current is \( 200 \mathrm{~A} \). Friction and windage losses are negligible. Calculate the speed, output power and torque of the motor when the motor operates at a total input current of \( 250 \mathrm{~A} \). (15 marks) (b) You are designing a switch-mode buck-regulator with a common input and output ground. The specifications are shown below: Supply voltage: \( 300 \mathrm{~V} \) DC Output voltage: \( 200 \mathrm{~V} \) DC Output power: \( 300 \mathrm{~W} \) Peak-to-peak inductor current ripple: Maximum \( 5 \% \) of the average input current Peak-to-peak output voltage ripple: Maximum \( 10 \mathrm{~V} \) Switching frequency: \( 20 \mathrm{kHz} \) Calculate the minimum values of the inductor and output capacitor, with the assumption of using ideal switching devices in the converter. (10 marks) (Total: 25 marks)