Electrotechnics N5 — Memo

August 2021 — N5 — Electrotechnics

N5 2021 Nated Engineering

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Q1— Section header —

1.1When the motor is at rest, the value of armature resistance is too low against the current flow through the armature. f the supply voltage is directly across these windings will cause a dangerous high armature or starting current

1.2

1.31 mark for labelled x axis 1 mark for labelled y axis 1 mark for correct shape and 3 marks for three curves drawn correctly (6\

1.4oss 5 000 + 250 5,25 kW 250 / 250 21 + 1 250 + ( 22 0,4 \ 258,8 V ( 258,8

Q2— Section header —

2.1.1135 coil 30 + j21,991 j23,579 30,919 < coil / (Z coil (37,197 < 36,24

2.3The total impedance of the circuit will simply be its resistance L = \ and Z = R The impedance (Z\ will be at its minimum The current drawn from the supply (I\, will be at its maximum [20]20

Q3— Section header —

3.1Copper loss Hysteresis loss Eddy current loss Stray loss 0,3 + 25(1/3\ 0,75 + 32,5(1/3\ 3,078 + j4,361 230 / 5,338

3.3.14 + j6 7,211 < 56,31 % 7,211 / 100 0,072 p.u S / V 15 X 10 / 1800 8,333 A (0,072 X 1800\ / 8,333

3.3.2Reg 15,576 8,333 Cos(56,31 36,87\ / 1800 0,068 p.u 6,8 % Reg 8,333[(8,639

Q4— Section header —

4.1(1 mark for a wattmeter\ (1 mark for the appropriate star connection diagram\ (1 mark for any appropriate labelling shown\ (3\

4.2

4.3S / V 2,8 / 33 84,849 A 84,849 3,6 305,455 < 0 305,455 + j0

Q5— Section header —

5.1Distribution factor is the ratio of the actual emf obtained to the emf that would be obtained if all coils were concentrated in one slot. (2\

5.2The slip produces the current in the rotor and develops the torque there is no slip, no current will be induced and no torque developed. (2\

5.3.1

5.3.2

5.4.160 f / p (60 50\ / 3 T / 60 1000 140\ / 60 14660,766 W 14,661 Rotor

Mark Allocation

Sections20 + 20 + 20 + 20 + 20 = 100 marks

Paper information

TitleMemo

SubjectElectrotechnics

LevelN5

Document typeNated Engineering

Year2021

MonthAugust

Pages8

Downloads6

Examination context

Decade2020s

Years ago5y

SeasonWinter (SH)

Start daySunday

Exam periodAugust 2021

Days since exam1,896

About Electrotechnics examination preparation

This TVET examination resource can be used as part of a structured revision programme. Past papers are most useful when learners attempt questions independently, work within a realistic time limit, and review their answers afterwards.

How to use this resource for revision

A TVET past examination paper is most useful when it is treated as an active revision exercise. Try the questions yourself before checking the corresponding memorandum. Where you make an error, identify the reason — was it a knowledge gap, a calculation mistake, an interpretation issue, or an examination technique problem?

For stronger examination practice, complete the paper without unnecessary interruptions and keep track of the questions that take the most time. Afterwards, review the memorandum and separate knowledge gaps from mistakes caused by interpretation, calculation, structure, or examination technique.

understanding question requirements

applying subject knowledge

working under time constraints

checking answers

identifying revision priorities

A practical revision approach

Start by completing the resource without looking at the memorandum. Review incorrect and incomplete answers afterwards and make a short revision list based on the areas that caused difficulty.

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