Electrical Technology Digital Electronics Memo 1 (English)

May-June 2025 — Grade 12 / Matric — Electrical Technology

Memo 2025 Grade 12 English

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🎯 200 marks 📄 5 pages 📝 52 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

Q1— Section header —

1.1[15] ch15

Q2— Section header —

2.1Health and safety equipment refer to any artefact which is manufactured, provided or installed Removing an emergency stop button from a motor control circuit. (2\

2.3The purpose of the act is to provide health and safety for people at work in general o create a safe environment for those who work with machinery

2.4Every employer is required by law An employee/learner with good discipline will not fool around with or disturb others in the workshop in such a way that it might cause an accident. [10] ch10

3.1Reactance is the opposition offered \( (3\

3.2.2Series I = 6,

3.2.3=6, (3\

3.2.4At resonance X \( 94,21 V VC = 164,22 V = 74,28 V = 120 V

3.4.20, 0, 0, 0, 0, (3\ 0,

4.1Coal There after the three phase voltage is stepped (220 for the transmission stage. After transmission, at the first distribution station this ultra high three

4.4.2(3\

4.4.4(3\

4.5Therefore, the current before power factor correction (50,94 A\ is greater than the current after power factor correction (45,58 A\ ch

4.6The capacitors in parallel with the load creates leading currents which cancels out some of the lagging currents drawn by the inductive load The phase angle. The same connection is used for star or delta connected loads.

5.4.20,8 S= (3\

5.4.3

5.4.424,06 ch 10

5.4.5Turns ratio: 13,89 (3\

5.5.1Delta elta configuration.

5.5.2For a step down transformer the secondary windings will be thicker

5.5.3If the sequencing of the phases incorrect, the phase relationship/sequencing of the magnetically connected phases will cause the secon dary phase voltages to be incorrect and it could cause damage to externally connected equipment.

5.6The term step refers to an increase in voltage

5.7.1Directional overcurrent relay

5.7.2The Buchholz relay as a safety device detects and responds to internal fault conditions. The Buchholz relay monitors the gas formation in the oil of the transformer under faulty conditions. (1\

5.7.3Under normal conditions the three voltages sum to zero. If there is an earth fault on one of the phases, the difference in voltages will operate the relay, [30] ch30

6.1.1Shaft Foot mount During operation t he fan blades on the rotor creates a flow of cool air through and around the motor to prevent the motor from overheating.

6.1.3Check the stator/frame for cracks. Check that the mounting bolts and nuts are properly tightened. Check if the end plates are securely fastened. Does the shaft turn freely by hand? Is the motor clean and free from excess grease?

6.1.4(a\ Acceptable The resistances of the three coils are all within 5% of each other. (2\ (b\ Acceptable (2\

6.2.1(3\

6.2.2(3\

6.2.3000 (3\ ch 12

6.2.4

6.2.5(3\

6.3.1delay timer because it is immediately energised when the start button is pressed. (2\

6.3.4The motor starts in star and the timer starts timing. As soon as the 3 seconds is reached the timer s contact will operate causing T N/C to open energizing MC and closing MC N/C. Simultaneously T N/O will close

7.1Reduced c ost Reduced space Flexibility Simplicity

7.2

7.3The normal operation of a plant can be observed electronically on a monitor keeping the operator away from dangerous machines. All operations are shown on the interface as machines turned on and faulty

7.4.3PLC software is a program that is written into the unit to control its functions. PLC software is the program used to compile the ladder logic program. A digital signal is a signal with a number of discrete steps.

7.6.1A 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. sensor is a device whose physical characteristics changes due to

7.6.2Temperature sensor Light sensor Overload sensor. Level sensor. (2\

7.6.3To detect the proximity of an object in relation to its distance Used to measure rotating speed (2\ ch 14

7.7START MC MC STOP N/O START MC MC MC

7.8.1The regenerat ive energy charges the DC capacitors that store it for future use. braking resistor is connected in the circuit to dissipate the energy in the form

7.9.1AC to DC Converter by switching the Insulated Gate Bipolar Transistor ON and OFF at a different frequency. The ON and OFF times (width of the pulses\ are carefully controlled (PWM\ with three pairs of switches (IGBTs\.

Mathematical Content

trig

Topics Identified

CircuitsMachines

Mark Allocation

Total200 marks

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

Paper information

SubjectElectrical Technology

Year2025

SessionMay-June

TypeMemo

PaperPaper 1

LanguageEnglish

Pages15

Downloads5

Examination context

Decade2020s

Years ago1y

Season—

Start day—

Exam period—

Days since exam—

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