Given an electrical load of 300 kW, which three UPS systems would represent an "N" configuration? (Choose three.)

Question

Options

• A1 UPS capable of supplying 400 kW
• B2 UPS paralleled; each UPS capable of 200 kW
• C3 UPSs paralleled; each UPS capable of 150 kW
• D4 UPSs paralleled; each UPS capable of 75 kW
• E5 UPSs paralleled; each UPS capable of 100 kW

• A
  74% (23)
• B
  13% (4)
• C
  6% (2)
• D
  3% (1)
• E
  3% (1)

Explanation

"N" configuration means having exactly the minimum UPS capacity required to support the load with zero redundancy - every unit present is necessary, and losing any one unit drops the system below the required load. The listed correct answer of A alone conflicts with the "choose three" instruction; the three options that actually represent N configuration are A, B, and D. Option A (1 x 400 kW) qualifies because that single unit alone covers the 300 kW load with no spare capacity. Option B (2 x 200 kW) qualifies because each unit provides only 200 kW - both are required, and losing either one leaves only 200 kW for a 300 kW load. Option D (4 x 75 kW) qualifies because all four units are needed to reach 300 kW, and losing any one leaves only 225 kW.

Option C (3 x 150 kW) is N+1: only two units are needed (2 x 150 = 300 kW), so the third is a redundant spare. Option E (5 x 100 kW) is N+2: only three units are needed (3 x 100 = 300 kW), leaving two spares.

Memory tip: To identify N, ask "how many units are the minimum to meet the load?" - if the count present equals that minimum, it is N. Any extras make it N+1, N+2, and so on.

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