A simple Zener diode shunt voltage regulator is to supply 12 V to a load which normally draws a load current which varies from 0 to 50 mA. The input voltage varies between 15 V and 18 V.

1.1 Calculate the maximum rated current value of a Zener device to be used.

1.2 Calculate the minimum power for the Zener that could be used safely.

1.3 If a 5 W rated Zener were to be used, calculate the range of possible RS. values and hence suggest a suitable standard E12 resistor value.

1.4 State four (4) conditions under which a Zener diode dissipates minimum power in a regulator circuit.

1. 3.A 3-phase ,Y- connected synchronous motor operates at 480 volt,50 Hz,2-pole,0.8 pf leading.The armature winding resistance is j1.5 ohm.The efficiency of the motor is 95%.The output torque of the motor at rated conditions is 350 Nm .Calculate: (a)the output power (b)the input power and the input current (c)the internal generated voltage Ea (d)the converted power (e)power losses (20 points)

The following three impedances are connected in series across a 40 V, 20 kHz supply: a 
resistance of 8 Ω, a coil of inductance 130 μH and 5 Ω resistance, and a 10 Ω resistor in 
series with a 0.25 µF capacitor. Sketch a neat diagram representing this network, and 
calculate:
5.1.1 The inductive and capacitive reactance’s. (4)
5.1.2 The magnitude and phase angle of the circuit impedance. (4)
5.1.3 The voltage drops across resistance, inductance and capacitance.

A microwave oven has a current of 5.0 amps going through it. It is plugged into a wall outlet with a voltage of 120 V. Calculate the resistance of the oven. Show your work using G.R.A.S.P.  (Given, Required, Analysis, Solution, Paraphrase) to show your work. (3 marks)