33 real LV Design & Panels questions from the Electrical Design bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is PCC vs MCC?
Junior
A.kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
B.power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors
C.free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
D.only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
2. Which term means: "power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors"?
A.PCC vs MCC — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
B.PCC vs MCC — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
C.PCC vs MCC — MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
D.PCC vs MCC — power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors
5. Which term means: "MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection"?
A.MCB vs MCCB vs ACB — ultimate breaking capacity proved by an O-CO sequence versus service breaking capacity proved by O-CO-CO after which the breaker must still carry rated current
B.MCB vs MCCB vs ACB — MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
C.MCB vs MCCB vs ACB — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
D.MCB vs MCCB vs ACB — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
A.IEC 61439 Form 1 has no separation, Form 2 separates busbars from units, Form 3 units from each other, Form 4 also separates terminals
B.ultimate breaking capacity proved by an O-CO sequence versus service breaking capacity proved by O-CO-CO after which the breaker must still carry rated current
C.MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
D.free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
8. Which term means: "free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets"?
A.DIALux — power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors
B.DIALux — IEC 61439 Form 1 has no separation, Form 2 separates busbars from units, Form 3 units from each other, Form 4 also separates terminals
C.DIALux — free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
D.DIALux — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
11. Which term means: "IEC 61439 Form 1 has no separation, Form 2 separates busbars from units, Form 3 units from each other, Form 4 also separates terminals"?
A.Forms of separation — IEC 61439 Form 1 has no separation, Form 2 separates busbars from units, Form 3 units from each other, Form 4 also separates terminals
B.Forms of separation — MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
C.Forms of separation — free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
D.Forms of separation — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
14. Which term means: "IEC 60947-4-1 requirement that after a short circuit the starter remains usable with no damage beyond light contact welding that is easily separated"?
A.Type-2 coordination — IEC 61439-1 allows 70 K at terminals for external conductors and 30–40 K on accessible enclosure surfaces, proved by test or calculation
B.Type-2 coordination — IEC 60947-4-1 requirement that after a short circuit the starter remains usable with no damage beyond light contact welding that is easily separated
C.Type-2 coordination — IEC 61439 factor applied to outgoing circuits loaded together, such as 0.8 for 4–5 circuits and 0.6 for 10 or more
D.Type-2 coordination — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
17. Which term means: "only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables"?
A.Discrimination — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
B.Discrimination — IEC 60947-4-1 requirement that after a short circuit the starter remains usable with no damage beyond light contact welding that is easily separated
C.Discrimination — MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
D.Discrimination — power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors
A.free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
B.MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
C.kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
D.ultimate breaking capacity proved by an O-CO sequence versus service breaking capacity proved by O-CO-CO after which the breaker must still carry rated current
20. Which term means: "ultimate breaking capacity proved by an O-CO sequence versus service breaking capacity proved by O-CO-CO after which the breaker must still carry rated current"?
A.Icu vs Ics — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
B.Icu vs Ics — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
C.Icu vs Ics — ultimate breaking capacity proved by an O-CO sequence versus service breaking capacity proved by O-CO-CO after which the breaker must still carry rated current
D.Icu vs Ics — IEC 60947-4-1 requirement that after a short circuit the starter remains usable with no damage beyond light contact welding that is easily separated
23. Which term means: "rating from running load kW and power factor plus the largest motor's starting kVA, with step loading limited to about 50–60% of rating per step"?
A.DG set sizing — MCB to 125 A and 10 kA per IEC 60898, MCCB 16–1600 A up to 100 kA with adjustable trips, ACB 630–6300 A drawout with full electronic protection
B.DG set sizing — IEC 61439 Form 1 has no separation, Form 2 separates busbars from units, Form 3 units from each other, Form 4 also separates terminals
C.DG set sizing — only the breaker nearest the fault trips, achieved by current, time or zone-selective interlocking and verified with manufacturer selectivity tables
D.DG set sizing — rating from running load kW and power factor plus the largest motor's starting kVA, with step loading limited to about 50–60% of rating per step
26. Which term means: "kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge"?
A.UPS sizing — IEC 61439-1 allows 70 K at terminals for external conductors and 30–40 K on accessible enclosure surfaces, proved by test or calculation
B.UPS sizing — free lighting design software that uses luminaire IES/LDT photometry to compute illuminance, uniformity and UGR against IS 3646 or EN 12464 targets
C.UPS sizing — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
D.UPS sizing — rating from running load kW and power factor plus the largest motor's starting kVA, with step loading limited to about 50–60% of rating per step
A.Rated diversity factor — IEC 61439 factor applied to outgoing circuits loaded together, such as 0.8 for 4–5 circuits and 0.6 for 10 or more
B.Rated diversity factor — IEC 61439-1 allows 70 K at terminals for external conductors and 30–40 K on accessible enclosure surfaces, proved by test or calculation
C.Rated diversity factor — power control centre distributes the incoming supply through ACBs and MCCBs, while a motor control centre houses starters for individual motors
D.Rated diversity factor — kVA from load watts over power factor with 20–25% margin, battery Ah from watts times backup hours over DC volts, efficiency and depth of discharge
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