Exin Updated CDCP Exam Questions and Answers by ren

A UPS (uninterruptible power supply) that is categorized as VFD class is not a fit for your mission-critical data centre, because it does not provide adequate protection against voltage and frequency variations. VFD stands for Voltage and Frequency Dependent, which means that the output voltage and frequency of the UPS depend on the input voltage and frequency. VFD UPSs are also known as offline, standby, or line-interactive UPSs. They typically switch to battery power only when the input power fails or goes beyond a certain threshold. However, this switching may cause a brief interruption or a transient in the output power, which can affect the performance and reliability of the ICT equipment. Moreover, VFD UPSs do not filter or regulate the input power, which means that they pass on any voltage or frequency fluctuations, harmonics, or noise to the output power. These power quality issues can also damage or degrade the ICT equipment and the data.

For your mission-critical data centre, you need a UPS that is categorized as VFI class, which stands for Voltage and Frequency Independent. VFI UPSs are also known as online, continuous, or double-conversion UPSs. They provide a constant and clean output power that is independent of the input power. VFI UPSs convert the input AC power to DC power, and then convert it back to AC power with the desired voltage and frequency. This double conversion process isolates the output power from the input power, and eliminates any power quality issues. VFI UPSs also have zero switching time, which means that they do not cause any interruption or transient in the output power when switching to battery power. VFI UPSs are designed to protect the ICT equipment and the data from any adverse effects of voltage and frequency variations, and to ensure the highest level of availability and reliability.

References:

1: CDCP Preparation Guide, page 17, section 2.3.1 2: Understanding UPS Classification: Fuji Electric’s Technical Guide3, page 1, section 1 4: Uninterruptible Power Supplies Key Product Criteria5, page 1, section 1 6: UPS Function: Reduced Input Voltage for VFDs - KEB7, page 1, section 1

The type of copper wire that is used for grounding the racks to the SRG (signal reference grid) in a data centre is braided copper wire or flat copper strip, according to the CDCP Preparation Guide1 and various web sources234. Braided copper wire or flat copper strip are preferred over thin or thick copper cable for grounding purposes, because they havelower impedance and higher surface area, which allow better dissipation of electrical noise and interference. Moreover, braided copper wire or flat copper strip are more flexible and durable than copper cable, which make them easier to install and maintain. Braided copper wire or flat copper strip should be connected to the SRG using exothermic welding or other code-compliant methods, and should follow the relevant standards and codes, such as ANSI/TIA/EIA-607 and NFPA 70.

References:

1: CDCP Preparation Guide, page 23, section 2.4.2 2: Signal Reference Grid | Enterprise Data Center Design and Methodology5, page 1, section 1 3: Grounding System Ground Rod Stacking Installation - Rain Bird6, page 1, section 1 4: SmartRack Copper Bus Grounding Bar - Eaton Website7, page 1, section 1

The last stage in stages of combustion is flaming fire, which occurs when the fuel vapors and oxygen are mixed in the right proportion and ignited by a flame or a spark. Flaming fire is characterized by visible flames, intense heat, and rapid oxidation. Flaming fire can cause severe damage to the data center equipment, personnel, and business continuity. Therefore, it is important to prevent or suppress flaming fire as soon as possible using appropriate fire detection and suppression systems.

References:

•EPI Data Centre Professional (CDCP®) Preparation Guide, page 31

•[Fire Detection and Suppression Systems for Data Centers]

Busbar trunking systems are a method of power distribution using rigid copper or aluminium conductors to distribute the power around a building. Busbar trunking systems have many advantages over cables, such as lower space requirements, higher short-circuit strength, lower fire load, and easier installation. One of the main advantages of busbar trunking is that it allows for flexibility in terms of power transmission and distribution. Busbar trunking systems can be easily relocated, modified, or expanded to accommodate changes in the building layout or load demand. Busbar trunking systems can also be fitted with various components, such as tap-off units, elbows, tees, and end feed units, to provide power to different locations and consumers. Busbar trunking systems can also be installed both overhead and under the raised floor, depending on the design and preference of the building.

References: Why I prefer busbar trunking systems more than cables | EEP, Why should you choose Busbar over Cable? - E+I Eng, Busbar VS Cables for Riser Applications - An Electrical Engineer.