6.1 Describe the following terms with reference to PLCs:
6.1.1 Hardware
6.1.2 Software
6.1.3 Opto-coupler
6.2 List THREE important hardware components of a PLC - NSC Electrical Technology Power Systems - Question 6 - 2020 - Paper 1
Question 6
6.1 Describe the following terms with reference to PLCs:
6.1.1 Hardware
6.1.2 Software
6.1.3 Opto-coupler
6.2 List THREE important hardware components of a PLC.
6... show full transcript
Worked Solution & Example Answer:6.1 Describe the following terms with reference to PLCs:
6.1.1 Hardware
6.1.2 Software
6.1.3 Opto-coupler
6.2 List THREE important hardware components of a PLC - NSC Electrical Technology Power Systems - Question 6 - 2020 - Paper 1
Step 1
6.1.1 Hardware
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Hardware refers to all the physical parts of a PLC that can be seen and touched. This includes components such as the central processing unit (CPU), input/output modules, and power supplies.
Step 2
6.1.2 Software
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Answer
Software pertains to the machine/graphical interface or programming languages utilized in operating a PLC. This could involve configuration tools, programming environments, and monitoring interfaces.
Step 3
6.1.3 Opto-coupler
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An opto-coupler is a semiconductor device that uses light to transmit signals between circuits, providing electrical isolation. This is crucial for protecting sensitive electronic components from high voltages.
Step 4
6.2 List THREE important hardware components of a PLC.
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Answer
Input Module
Output Module
Central Processing Unit (CPU)
Step 5
6.3 State THREE safety precautions to be considered when connecting a PLC to the supply.
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Ensure all power connections are secure to prevent electrical arcing.
Use circuit protection devices like fuses or circuit breakers.
Verify that the wiring is adequate for the current load to avoid overheating.
Step 6
6.4.1 Draw the logic gate symbol of the ladder logic circuit in FIGURE 6.4.
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The logic gate symbol for the ladder logic circuit will depict a physical representation of the inputs A and B leading to the output Q through appropriate AND/OR gates.
Step 7
6.4.2 Complete the truth table in FIGURE 6.4.2 below by writing ONLY the state of the output on the ANSWER SHEET FOR QUESTION 6.4.2.
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Input A
Input B
Output Q
0
0
0
0
1
0
1
0
0
1
1
1
Step 8
6.5 State ONE application of an inductive proximity sensor.
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An inductive proximity sensor can be used in counting applications for detecting the presence of metal objects as they pass by.
Step 9
6.6.1 State whether the logic program represents an ON-delay timer contact or an OFF-delay timer contact.
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The logic program represents an ON-delay timer contact.
Step 10
6.6.2 Describe the sequential operation of the logic program when the push button (I1) is pressed.
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When the push button (I1) is pressed, the timer (TD) is energized, and the normally closed contact of the timer opens, keeping the output Q low. After 15 seconds, the output Q will switch to high, indicating that the timer has completed its delay.
Step 11
6.8.1 State the conditions of the red lamp and the green lamp before the start button is pressed.
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Before the start button is pressed, the red lamp will be OFF, and the green lamp will also be OFF.
Step 12
6.8.2 Explain the function of MC in the circuit.
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The function of the MC (contactor) is to energize and de-energize the circuit. When powered, it closes the contacts to allow current to flow, which activates the subsequent devices.
Step 13
6.9 Explain the principle or operation of the variable speed drive (VSD).
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A variable speed drive (VSD) controls the speed of an electric motor by varying the frequency and voltage of the electrical supply. It converts AC input power to DC, using this to adjust the speed of the motor based on the required output.
Step 14
6.11.1 Describe the duration of the switching time at area A and area B with reference to pulse width modulation in FIGURE 6.11.
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Area A has a shorter switching time compared to area B, which indicates that the pulses in area A are narrower than those in area B, leading to different duty cycles and effects on motor performance.
Step 15
6.11.2 State the effects the width of the pulses has on the average output voltage in FIGURE 6.11 A.
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The greater the width of the pulses, the higher the average output voltage. This is because wider pulses increase the effective voltage applied to the load, improving performance.
Step 16
6.12 State THREE precautions that must be considered when working with a VSD.
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Avoid long cable runs to reduce losses.
Ensure adequate cooling for the VSD.
Follow the manufacturer’s installation and safety guidelines.
