Electrical Technology Digital Electronics Memo 1 (English)

November 2022 — Grade 12 / Matric — Electrical Technology

Memo 2022 Grade 12 English

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🎯 200 marks 📄 4 pages 📝 88 items found ∑ 1 math symbols 📚 2 topics

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2.1All calculations must show the formulae.

2.2Substitution of values must be done correctly.

2.3All answers MUST contain the correct unit to be considered.

2.4Alternative methods must be considered, provided that the correct answer is obtained.

2.5Where an incorrect answer could be carried over to the next step, the first answer will be deemed incorrect. However, should the incorrect answer be carried over correctly, the marker has to re calculate the values, using

Q1— Section header —

1.1(1\

1.2(1\

1.3(1\

1.4(1\

1.5(1\

1.6(1\

1.7(1\

1.8(1\

1.9(1\

1.10(1\

1.11(1\

1.12(1\

1.13(1\

1.14(1\

1.15(1\ [15] Electrical Technology: Power Systems DBE/ November 2022 NSC15

2.1The employer should be respected The employer should not be discriminated against Your right to fair labour practices. Your right to work reasonable hours. Your right to belong to a trade union. Your right to earn a living wage.

2.2Move in an orderly manner. Follow the evacuation route as displayed in your workshop. Move to the designated assembly point in a calm and orderly manner. (2\

2.3Misusing equipment is a dangerous practice which might damage the equipment and render it unsafe, compromising the safety and or threatens the health of others. (2\

2.4An employer shall not dismiss an employee without the correct procedures being followed. An employer shall not reduce the remuneration of an employee as punishment. Alter terms of condition of employment to one that is less favourable.

2.5Quantitative risk analysis Qualitative risk analysis (2\ [10] Electrical Technology: Power Systems DBE/10

3.1Inductance is the created back emf in an inductor that tends to oppose changing electric current passing through it. Inductance is the tendency of a coil to oppose a change in current flowing through it

3.2.1(2\

3.2.2(2\

3.3.1(3\

3.3.2(3\

3.3.3=250 mH No mark for manipulation (3\

3.3.4A lagging power factor is when the current lags the voltage in an RLC circuit. (1\ Rotation 84,77

3.3.5At resonance, the circuit becomes resistive because the capacitive reactance and inductive reactance cancels each other, resulting with an in phase relationship between current and voltage. (2\

3.4.1(3\

3.4.2(3\

3.4.3(3\

3.4.4The circuit has a lagging power factor as the inductive current is greater than the capacitive current. (2\

3.5.1A parallel RLC circuit NOTE: Because of the error in the prescribed textbook 1 mark will be allocated if the learner indicates that response A = series RLC (2\

3.5.2The impedance will be maximum and the current will be minimum (2\

3.5.3When the frequency increase to resonant frequency the impedance increases. When the frequency increase above the resonant frequency, the impedance decreases. NOTE: The impedance increases with an increase in frequency = 1 mark

4.1.1The phasor diagram represents positive phase sequence because the directio n of rotation is anti clockwise (R

4.1.2Phase voltage, because it is the voltage between R (Line 1\ and neutral (N\

4.2Active power or real power refers to the capacity of a circuit for performing work in a particular time

4.3By stepping up the voltage in transmission lines the current flowing th ough the lines are reduced

4.4NOTE: 3 marks = 1 mark for each correct phase or line 1 mark for the neutral

4.5Power is distributed to substations at 22 kV (towns, industrial and farms\ It is then stepped down to 11 kV for intermediate substations. It is finally stepped down to 380 V/220 V at distribution substations.

4.6.1(3\

4.6.2(3\

4.6.3(3\

4.6.4(3\

4.6.5(3\

4.7.1It can measure both balanced and unbalanced loads. The power consumption of each phase can be determined. (2\

4.7.2Three wattmeters are required for an unbalanced load. The terminals of the load must be available to connect the wattmeters if no neutral line exists, or if the load is in delta. The power factor cannot be determined and must be measured

4.7.3Because it is a balanced load P =P =P OR (3\ [35]35

5.1Mutual induction is when the magnetic flux of one coil cuts the conductors of an adjacent coil and induces an emf inside that coil without being electrically connected. (3\

5.2.1Transformer ratio Voltage rating Current rating Power rating Efficiency Size Power factor Frequency (3\

5.2.2Star (1\

5.3.1Copper losses are losses due t o the internal resistance of the copper conductors in the coils, which occur in the form of heat when current flows.

5.4Dry type transformers are equipped with tubular radiators around which air circulates cooling the windings therefore controlling insulation failure. (2\

5.7.3(3\

5.7.4(3\ [30] Electrical Technology: Power Systems 11 DBE/ November 2022 NSC Marking30

6.1Wound rotor age rotor (2\

6.2.1Rated speed is the maximum speed at which the motor effectively works. Full load speed is the speed when maximum load is connected to the motor. (2\

6.2.2(3\

6.2.3(3\

6.3Check if there is any play on the axis. Check if the axis turns freely by hand. Check if the bearings work smoothly when turned by hand. Check for any excessive grease and dust on the bearing bushes. (2\

6.4.1(3\

6.4.2(3\ Electrical Technology: Power Systems 12 DBE/ November 2022 NSC Marking Guidelines

6.4.3(3\ = 2783,19 W

6.5(3\

6.6.1Overload Normally Closed contact (1\

6.6.2MC N/O is a hold out contact ensuring that the timer relay and

6.6.3Interlocking ensures that MC and MC do not energise simultaneously. (2\

6.6.4The moment the timer has timed through, T N/C will open, de energising MC This closes MC N/C and TN/O

7.1It is easy to trace fault with a multimeter by following wiring diagram.

7.2.1A sensor is a device that detects and converts an environmental condition into an electrical signal that can be used by another device for a particular purpose. (2\

7.2.2After receiving data from a temperature sensor, the PLC runs it through the program and update the outputs accordingly. (2\

7.2.3Mining drills Battery chargers Electric motors (2\

7.3.1Forward Reverse starter. (1\

7.3.2atching makes it possible for circuit to be triggered 'on' and remain 'on' regardless of whether the activating trigger has been removed. (3\

7.3.3NOTE: If a learner makes use of markers and the program operates correct, marks will be awarded accordingly. (8\ Start MC

7.5A marker is a storage memory which indicates that certain processes have been completed and other devices can be switched either ON or OFF. (2\

7.6.1The converter operates on the process of rectification; each pair of diodes rectify one of the three phases. (2\

7.6.2 The filter circuit uses capacitors to smooth out ripple voltages ensuring a pure DC voltage on the DC bus (2\

7.6.3 The inverter changes the DC voltages on the DC bus into pulses using Insulated Gate Bipolar Transistors.

7.6.4 Energy savings Better speed control of motors Better power factor Smooth starting of motors (2\

7.7Lifts Cranes Mine Winding gear Electrical Locomotives Electric Coal Hauling Trucks (2\ [40] TOTAL40

Mathematical Content

trig

Topics Identified

CircuitsMachines

Mark Allocation

Total200 marks

Sections15 + 10 + 35 + 35 + 30 + 35 + 40 = 200 marks

Paper information

SubjectElectrical Technology

Year2022

SessionNovember

TypeMemo

PaperPaper 1

LanguageEnglish

Pages14

Downloads7

Examination context

Decade2020s

Years ago4y

SeasonSpring (SH)

Start daySaturday

Exam periodNovember 2022

Days since exam1,450

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