This section provides a quick preview of questions from the document. It may not display every question or the complete wording of each one. For the full content, including diagrams, tables and other information, view the original PDF above.
Q1— Section header —
1.1Indicate whether the following statements are TRUE or FALSE by writing only 'True' or 'False' next to the question number (1.1.1
1.1.5\in the ANSWER BOOK.
1.1.1An ohmmeter is used to measure resistance on a live circuit.
1.1.2A wattmeter consists of two coils.
1.1.3An insulation resistance tester cannot be used as a continuity tester.
1.1.4A frequency meter is connected in parallel in a circuit.
1.1.5
1.2A I B I + +
1.3Calculate the frequency at which a 0,2 H inductor will have a reactance of (2\
1.4The power factor is the ratio between the true power and apparent power. It is important to have an improved power factor Mention at least THREE methods used to improve the power factor. (3\
1.5An alternating current with a frequency of 100 Hz has an RMS value of 2,121 A. Write down the equation for the instantaneous value of this current. (5\ (12041004\
1.6Explain each of the following terms with reference to a sine wave:
1.6.1Peak value
1.6.2
1.7What is another name for the RMS value of an alternating quantity? (1\ [30]30
Q2— Section header —
2.1A 300 kW, three phase AC motor is connected in delta and the supply voltage is 380 V. The power factor is 0,96 Calculate:
2.1.1The line current drawn by the motor (3\
2.1.2The phase current of the motor (2\
2.2Describe how nuclear energy is generated. (6
2.3Explain the function of each of the following:
2.3.1Lightning arrest
2.3.215
Q3— Section header —
3.1Draw a neatly labelled diagram of a TN S earthing system. (7
3.2Give FOUR reasons for earthing the neutral of a low voltage (LV\stem. (4\
3.3Define each of the following terms used for earthing according to current regulations and standards:
3.3.1Earth continuity conductor
3.3.215
Q4— Section header —
4.1We test machines and transformer s so that we can find out about operating characteristics, losses and efficiency
4.1.1Name TWO tests that can be performed on a transformer (2\
4.1.2tate the purpose of each test named above in 4.1.1 (2\
4.2Explain how a potential transformer is connected in a circuit. (2\
4.3A three phase, delta star connected transformer delivers a line voltage of 346,41 V when connected to a 6 kV supply Calculate:
4.3.1The transformer ratio (4\
4.3.2The primary phase current when the transformer draws its full load current of 120 A from the supply (2\
4.4Give THREE advantages of delta star connected transformer. (3\ 4.
4.5.1 What is hysteresis loss? (2\
4.5.2 Mention THREE factors on which the hysteresis loss depends on (3 [20]20
Q5— Section header —
5.1A four pole wave wound series motor having 315 armature conductors draws a current of 50 A from a 1 000 V supply. The armature and series field respectively. The flux per pole is 0,1 Wb. Calculate:
5.1.1The induced emf
5.1.2
5.2Complete the following sentences by writing only the missing word or words next to the question number (5.2.1
5.2.4\n the ANSWER BOOK.
5.2.1Protective devices in motor starters include a/an a/an (2\
5.2.2To reverse the direction of rotation of a DC motor, the rule is to (2\
5.2.3(1\
5.2.4dangerously high speed. (1\
5.3Compare the characteristics of squirrel cage motors and wound rotor motors
5.3.1Rotor construction
5.3.2Starting
5.3
5.4Name TWO types of mechanical losses that occur in an induction motor. (2\ [20] TOTAL: 100 (12041004\20