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Power Redundancy & UPS Systems Flashcards

7 cards from real ATP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. Which UPS topology provides zero transfer time during a utility power failure?

    Answer: Double-conversion (online) UPS

    Double-conversion online UPS continuously powers the load from the inverter, so there is no transfer time when utility power fails.

  2. In a 2N power redundancy configuration, what happens to the total capacity when one PDU path fails?

    Answer: The remaining path carries 100% of the load at full rated capacity

    In a 2N configuration, each path is sized to carry 100% of the load, so a single path failure results in the surviving path assuming the full load.

  3. A static transfer switch (STS) typically has a transfer time measured in:

    Answer: Milliseconds (4–8 ms)

    Static transfer switches typically switch between power sources within 4–8 milliseconds, fast enough for most IT equipment.

  4. Which of the following best describes an N+1 UPS redundancy model?

    Answer: One extra UPS module is deployed beyond the minimum needed to support the load

    N+1 redundancy means one additional UPS module is added beyond the N modules required to carry the load, allowing any single module to fail without service interruption.

  5. What is the primary advantage of a modular UPS over a traditional monolithic UPS in a data center?

    Answer: Scalability and hot-swap capability for individual power modules

    Modular UPS systems allow individual power modules to be added or replaced without shutting down the system, enabling scalable and maintainable redundancy.

  6. When performing a UPS maintenance bypass, what is the critical safety concern the technician must verify before switching to bypass?

    Answer: That the bypass source is synchronized with the UPS output

    Before engaging maintenance bypass, the bypass source must be synchronized in phase and voltage with the UPS output to prevent a voltage step or surge to the load.

  7. A data center UPS is rated at 500 kVA with a 0.9 power factor. What is the maximum kW load it can support?

    Answer: 450 kW

    Real power (kW) = apparent power (kVA) × power factor, so 500 kVA × 0.9 = 450 kW.