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Q1— Section header —
1.1FIGURE shows circuit diagram of a stove. Study the circuit diagram and answer the questions. FIGURE 1
1.1.1State the colour coding for live indicated by letter A, neutral indicated by letter B and earth indicated by letter C. (3\
1.1.2State the size of the conductors A & B mentioned in QUESTION
1.1.1(1\
1.1.3What is the size of the circuit breaker indicated by the letter D
1.1.4Identify the components indicated by letter E and F. (2\
1.2Name THREE types of valves that are found i pressur type geyser.
Q2— Section header —
2.1Make a neat label ed sketch of a thermal magnet type circuit breaker that i
2.2Explain how the following is achieved in the above circuit breaker
2.2.1Time delay
2.2.210
Q3— Section header —
3.1FIGURE 2 shows a DC fluorescent lamp circuit. Name the components indicated in the sketch by writing only the name of each component
3.1.5
3.2Briefly explain why a reversing switch is required in a DC fluorescent lamp circuit. (2\
3.3State THREE applications where sodium vapour discharge lamps can be used. (3\ [10] 1104126310
Q4— Section header —
4.1Average value (2\
4.2Frequency of the wave (2\
4.3Period time (1\
4.4Crest factor (2\
4.5Instantaneous voltage 10 ms after t = 0 seconds (3\ [10]10
Q5— Section header —
5.1Calculate the inductive reactance (3\
5.2Calculate the capacitive reactance (3\
5.3State whether the current in this circuit is leading or lagging. Explain why this is the case. (2\
5.4Draw a voltage phasor diagram representing the circuit in FIGURE 3 . Your drawing does not have to be to scale. (2\ [10] 1104126310
Q6— Section header —
6.1A three phase 10 W, 415 V motor is started in star and runs in delta. Calculate the phase voltage when the starter is in the:
6.1.1tar position (2\
6.1.2elta position (1\
6.2A three phase delta connected motor draws 250 A from a 415 V supply at a lagging power factor of 0
6.2.1pparent power (2\
6.2.2nput power (2\
6.2.3hase current of the motor winding (3\ [10]10
Q7— Section header —
7.1Explain the operation of a transformer under the following headings:
7.1.1Method of reduction of eddy current
7.1.2
7.2A three phase step down tr ansformer has a delta connected primary and a star
7.2.1The turn ratio
7.2.2The primary line current if the secondary line current is 100
7.2.3The size of the transformer in MVA (2\ [10] 1104126310
Q8— Section header —
8.1State the function of the following components of a DC machine
8.1.1Bearings
8.1.2Commutator
8.1.3Interpoles
8.1.4
8.2Briefly explain the need of a series resistor when starting a large DC motor (2\ [10]10
Q9— Section header —
9.1Explain what is meant by synchronous speed with reference to three phase induction motors. (1\
9.2Name any THREE types of single phase AC motors. (3\
9.3
9.4State TWO disadvantages of wound rotor motors. (2\ [10]10
Q10— Section header —
10.1State TWO types of moving iron instruments. (2\
10.2Make a drawing of each of the following
10.2.1A neat label led circuit diagram of a half wa ve rectifier using one diode (3\
10.2.2Waveforms to show the input wave and output wave of the circuit QUESTION
10.2.1if the supply is sinusoidal (4\
10.3State ONE use of a diode. 1\ [10] TOTAL: 100 1104126310