CDCP Data Center Power Infrastructure 2

Question 1

What is the purpose of a static transfer switch (STS) in a data center power system?

Accepted Answer

To automatically transfer an IT load from one power source to another in less than a quarter cycle (4ms or less) without interruption

Answer

An STS uses solid-state electronics to transfer critical loads between two independent power sources in less than 4 milliseconds, fast enough that IT equipment does not experience a power interruption.

Question 2

What is the purpose of an isolation transformer in a data center power distribution system?

Accepted Answer

To electrically isolate equipment from the power distribution system, reduce common-mode noise, and provide a separately derived system for grounding

Answer

Isolation transformers provide galvanic isolation between primary and secondary circuits, eliminating common-mode noise, providing a new neutral-ground bond, and improving electrical safety.

Question 3

What does 'kVA' measure in the context of data center power systems, and how does it differ from kW?

Accepted Answer

kVA (kilovolt-amperes) measures apparent power including reactive components; kW measures real (active) power. The ratio kW/kVA is the power factor.

Answer

kVA is apparent power (voltage × current), while kW is real power (the work-performing component). Power factor (PF) = kW/kVA; modern IT equipment typically has PF of 0.9–0.99.

Question 4

In a 2N UPS configuration, how is the IT load typically distributed between the two UPS systems during normal operation?

Accepted Answer

Each UPS carries 50% of the total IT load, so each operates at 50% capacity and either can support 100% of the load alone if the other fails

Answer

In a 2N configuration, both UPS systems are active and each carries half the load, ensuring that if one fails the other can immediately assume 100% of the load without any switching.

Question 5

What is the function of a power distribution unit (PDU) in a data center?

Accepted Answer

To receive high-voltage power from UPS or transformers and distribute it to individual racks at the appropriate voltage and with circuit protection

Answer

A PDU takes incoming power from the UPS or facility transformer and distributes it to multiple branch circuits serving individual racks, providing overcurrent protection and often metering.

CDCP - Certified Data Centre Professional Practice Test

CDCP - Certified Data Centre Professional Practice Test

CDCP Data Center Power Infrastructure 2