A diesel electric generating station supplies an output of 25 kW. The calorific value of the fuel oil used is 12,500 Kcal/Kg.If the overall efficiency of the unit is 35%, calculate the mass of oil required per hour.

a. 4.91 kg

b. 54 kg

c. 7.89 kg

d. 1.34 kg

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)

Question 3  (IEIIQ16)

A 3 W rated Zener diode is used in a shunt voltage regulator circuit to supply a dc output of 12 V to a variable load with a minimum resistance of 240 Ω. The supply voltage varies between 20 V and 24 V.

3.1    Draw the circuit diagram.

3.2    Calculate the range of series resistance that may safely be used in this circuit. Select a single suitable standard value.

3.3    Calculate the maximum power rating required for the series resistor.

Question 4  (IEIIQ17)

A simple Zener voltage regulator is required to provide a steady regulated output voltage of 10 V under a maximum load of 80 mA, while the input voltage to the regulator varies between 12 V and 14 V.

17.1  Calculate the maximum rated current value of a Zener diode to be used

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

17.3  If a 5 W rated Zener were to be used in this circuit:

(i)      Calculate the maximum rated current value of a Zener device to be used

(ii)      Calculate the range of possible RS.  limiting resistor values.

(iii)     Suggest a suitable standard E12 resistor value

Question 5  (IEIIQ18)

A simple Zener shunt voltage regulator is to supply a 10 V to load of 100 mA, the input supply voltage varies between 15 V and 20 V.

5.1    Draw the circuit diagram.

5.2    Calculate the minimum power for the Zener that could be used safely in this circuit.

5.3    Using a Zener diode with a power rating of twice this minimum value.

5.4    Calculate the range of series resistance that may safely be used in this circuit and suggested a suitable standard resistance value.

Question 6  (IEIIQ19)

A voltage regulator is required to provide a regulated terminal voltage of 25 V at a maximum load of 150 mA. The input volage varies between 50 V and 75 V dc.

6.1    Calculate the minimum power for the Zener that could be used safely in this circuit.

6.2    If a 30 W rated Zener is used, calculate the range of possible series resistance, RS. values and suggest a suitable standard E12 resistor value.