ETC ETC Electrical Systems & Instrumentation 2 — Questions and Answers
Question 1: What is the function of a rectifier in an electrical system?
- Converts AC to DC (Correct answer)
- Converts DC to AC
- Steps up AC voltage
- Filters out harmonics
Correct answer: Converts AC to DC
A rectifier converts alternating current (AC) into direct current (DC) using diodes or thyristors.
Question 2: Which grounding method directly connects the neutral point of a transformer to earth?
- Solid grounding (Correct answer)
- Resistance grounding
- Isolation
- Floating neutral
Correct answer: Solid grounding
Solid grounding directly connects the neutral to earth, providing a low-impedance fault path for safety.
Question 3: What is the purpose of a power factor correction capacitor bank?
- To increase system frequency
- To reduce reactive power demand and improve power factor (Correct answer)
- To increase voltage at the load
- To filter harmonic distortion
Correct answer: To reduce reactive power demand and improve power factor
Capacitor banks supply reactive power locally, reducing the reactive current drawn from the utility and improving power factor.
Question 4: What does IP65 rating indicate for electrical enclosures?
- 65 volts maximum operating voltage
- Dust-tight and protected against water jets (Correct answer)
- 65 ampere current rating
- 65% efficiency rating
Correct answer: Dust-tight and protected against water jets
IP65 means the enclosure is completely dust-tight (6) and protected against low-pressure water jets from any direction (5).
Question 5: Which device is used to measure the insulation resistance of electrical cables?
- Clamp meter
- Megohmmeter (Correct answer)
- Oscilloscope
- Power quality analyzer
Correct answer: Megohmmeter
A megohmmeter applies high DC voltage to measure insulation resistance, typically in megaohms, to assess cable integrity.
Question 6: What is the purpose of a Variable Frequency Drive (VFD) in motor control?
- To reverse the direction of three-phase motors only
- To control motor speed by varying supply frequency and voltage (Correct answer)
- To provide overload protection only
- To convert single-phase to three-phase power
Correct answer: To control motor speed by varying supply frequency and voltage
A VFD adjusts the frequency and voltage supplied to a motor, allowing precise speed control and energy savings.
ETC ETC Electrical Systems & Instrumentation 2
What is the function of a rectifier in an electrical system?