2026年最新のCDCS問題集レビュー専門クイズ学習材料
CDCSテスト準備トレーニング練習試験問題 練習テスト
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質問 # 70
You are working on the design of a new facility. The electrical riser of the building with high current power is located close to the area where sensitive IT equipment in the computer room will be located.
What should you recommend to reduce the amount of EMF coming from the electrical riser?
- A. Install single-phase power cabling
- B. Install three-phase power cabling based on three individual core wires
- C. Install three-phase power cabling based on a combined cable (e.g. XLPE etc.)
- D. Install bus bar trunking
正解：C
解説：
To reduce Electromagnetic Fields (EMF) emanating from the electrical riser near sensitive IT equipment, three-phase power cabling in a combined cable (such as XLPE) is effective. Combined cabling helps reduce EMF by keeping the conductors tightly packed, which minimizes magnetic fields generated by current flow.
Cables like XLPE (cross-linked polyethylene) also offer better insulation, which helps mitigate EMF interference with nearby IT equipment.
Detailed Explanation:
Using a combined three-phase cable reduces EMF because the magnetic fields generated by each phase tend to cancel each other out when in close proximity. This arrangement helps reduce the overall magnetic field strength. In addition, XLPE and similar materials provide good insulation, making them a preferred choice for reducing EMF emissions around sensitive equipment.
EPI Data Center Specialist References:
EPI data center best practices recommend mitigating EMF interference through combined cabling arrangements, especially near areas where sensitive IT equipment is located. Reducing EMF is crucial to maintaining equipment reliability and ensuring compliance with safety standards.
質問 # 71
When designing a data center network, your company wants to minimize the number of network switches to manage.
What type of physical cabling layout would be the best choice?
- A. EoR (End of Row) design
- B. ToR (Top of Rack) design
- C. Star network design using coaxial cables
- D. It does not matter as the number of switches is not influenced by the physical cabling layout
正解：A
解説：
An End of Row (EoR) design minimizes the number of network switches, as multiple racks can share a single switch at the end of a row, reducing switch counts and simplifying management. This design centralizes network switching to fewer points, which reduces the complexity and number of switches required compared to a Top of Rack (ToR) design, where each rack typically has its own switch.
Detailed Explanation:
In EoR designs, each row has a single network switch that handles the connections for all racks within that row. This reduces the number of individual switches needed and centralizes network management, which is ideal for minimizing equipment and simplifying infrastructure in the data center.
EPI Data Center Specialist References:
EPI promotes the EoR design as a way to reduce switch counts and streamline management in data centers. This configuration allows for easier scaling and maintenance while maintaining efficient network connectivity.
質問 # 72
Which class of UPS is ideal for data centers?
- A. VFI (Voltage and Frequency Independent)
- B. First class
- C. VFD (Voltage and Frequency Dependent)
- D. VI (Voltage Independent)
正解：A
解説：
IEC 62040 defines UPS topologies:
* VFD: Line-interactive; dependent on mains.
* VI: Stabilizes voltage but not frequency.
* VFI: Double-conversion online; fully isolates output from mains fluctuations.
Data centers require continuous, clean, and stable power. VFI is the only topology that protects against both voltage and frequency disturbances, meeting ANSI/TIA-942 Rated-3/4 requirements.
Thus, VFI is the ideal UPS class.
References: IEC 62040-3, ANSI/TIA-942-B §6.2.
質問 # 73
When are the wet bulb and dry bulb temperatures identical?
- A. When the relative humidity is at the best practice value for relative humidity, being 50% RH
- B. When the dry bulb's temperature is at the lowest allowable temperature for IT equipment as per ASHRAE
- C. When the dry bulb's temperature is at the highest allowable temperature for IT equipment as per ASHRAE
- D. When the relative humidity is 100%
正解：D
解説：
The wet bulb and dry bulb temperatures become identical when the relative humidity reaches 100%. At this point, the air is fully saturated with moisture, meaning it can no longer absorb additional water vapor. As a result, the rate of evaporation decreases, and there is no difference between the dry bulb and wet bulb temperatures.
Detailed Explanation:
The dry bulb temperature measures the air temperature, while the wet bulb temperature takes into account the cooling effect of evaporation. When relative humidity is at 100%, the air has reached its saturation point, and no further evaporation occurs. This causes both the wet bulb and dry bulb thermometers to display the same temperature reading. This condition is critical in understanding environmental conditions, particularly in HVAC and data center environments, where humidity control is essential to avoid equipment overheating or corrosion.
EPI Data Center Specialist References:
The EPI Data Center Specialist training includes understanding humidity levels and their impact on data center environments. Knowing when wet bulb and dry bulb temperatures align helps data center operators manage moisture levels effectively, which is essential for preventing issues related to high humidity, such as condensation on IT equipment.
質問 # 74
Where should perforated tiles be installed?
- A. One tile per rack in front
- B. Every 5th rack
- C. As close to AC as possible
- D. At the back of racks
正解：A
解説：
Perforated tiles should be located in front of equipment racks, aligned with cold aisles, to deliver supply air directly to server intakes. Best practice is one perforated tile per rack, adjusted based on airflow requirements and rack load.
* Placing tiles at the back (A) disrupts airflow.
* Spacing every 5th rack (B) provides insufficient cooling.
* Placing near AC (D) causes uneven distribution and pressure loss.
Thus, option C is correct.
References: ASHRAE TC 9.9 "Airflow Management," ANSI/TIA-942-B §6.5.
質問 # 75
Racks with 1.0 m depth and cold aisle containment with 3 perforated tiles are used. What aisle pitch is recommended?
- A. 8 tiles pitch rule
- B. 7 tiles pitch rule
- C. 10 tiles pitch rule
- D. 5 tiles pitch rule
正解：B
解説：
The aisle pitch is the total width of a rack row plus cold aisle plus rack row. For 1.0 m racks on each side with cold aisle containment, ASHRAE and TIA-942 recommend the 7-tile rule (each tile ~0.6 m). This ensures enough width for equipment clearance, airflow distribution, and human access.
* 5-tile pitch is too narrow, restricting containment effectiveness.
* 8-10 tiles may be used in some hyperscale layouts but are not standard for 1 m racks.
Thus, the correct design recommendation is the 7 tiles pitch rule.
References: ANSI/TIA-942-B §6.3.6 (Aisle Spacing), ASHRAE TC 9.9 "Airflow Management Best Practices."
質問 # 76
The temperature in the computer room is being increased from 18°C/64°F to 27°C/81°F.
What is the impact, if any, on the amount of gas required to suppress a fire assuming the gas is a Halocarbon?
- A. The change to the amount of gas cannot be determined without knowing the change in humidity as well
- B. The amount of gas required will be higher
- C. The amount of gas required will not change
- D. The amount of gas required will be lower
正解：D
解説：
With Halocarbon fire suppression systems, as the temperature increases, the amount of gas required for effective suppression decreases. This is because Halocarbon agents are stored as a liquid and discharge as a gas, expanding more at higher temperatures. As a result, less agent is needed at higher room temperatures to achieve the desired concentration for fire suppression.
Detailed Explanation:
Halocarbons rely on specific volumetric concentrations to suppress fires. Higher temperatures cause the agent to expand more rapidly, effectively filling the protected area with less agent needed to reach the required concentration. This is in contrast to some other gases, where temperature changes might not have the same effect on discharge quantities.
EPI Data Center Specialist References:
EPI data center training on fire suppression indicates that understanding the physical properties of agents like Halocarbons is key for correct system sizing. As the temperature rises, the gas expands more readily, thus requiring adjustments in the amount needed for effective coverage.
質問 # 77
Is it allowed to make design changes during the implementation phase?
- A. Any change is fine as long as it is within the scope of the project.
- B. Only when there is a strong business and/or technical justification.
- C. Yes, but only when time to implement is not exceeded.
- D. No, after a design freeze no further changes are allowed.
正解：B
解説：
Design changes during the implementation phase are generally allowed only when there is a strong business and/or technical justification. Changes at this stage can lead to delays, increased costs, or compromise design integrity. Thus, a rigorous assessment is required to ensure any modifications are essential and provide clear benefits or address critical issues.
Detailed Explanation:
Changes post-design freeze should be minimized to avoid scope creep and additional costs. However, if a technical issue arises that would affect operational goals, or a business need warrants modification, justified changes are permissible, following an impact assessment and approval process.
EPI Data Center Specialist References:
EPI project management guidelines recommend a controlled change management process during implementation, allowing changes only when they align with critical objectives or address unforeseen issues that affect the project's success.
質問 # 78
You are allowed to use a calculator for this question.
A computer room has a net volume of approximately 2,500 m³ / 88,287 ft³.
The temperature is 20 °C / 68 °F.
The required design concentration is 7%.
The S-Factor is 0.1359 (metric) / 1.885 (imperial).
Calculate the amount of gas required for this computer room based on FM200. What is the correct weight?
- A. Approximately 410 kg / 900 lbs
- B. Approximately 1,390 kg / 3,000 lbs
- C. Approximately 820 kg / 1,800 lbs
- D. Approximately 1,640 kg / 3,600 lbs
正解：C
解説：
The amount of FM200 gas required can be calculated using the formula:
Weight of Gas=Net Volume×Design Concentration×S-Factor\text{Weight of Gas} = \text{Net Volume}
\times \text{Design Concentration} \times \text{S-Factor}
Weight of Gas=Net Volume×Design Concentration×S-Factor
Using metric units:
* Net Volume: 2,500 m³
* Design Concentration: 7% (or 0.07)
* S-Factor: 0.1359
Calculation:
2,500 m3×0.07×0.1359=821.325 kg2,500 \, \text{m}^3 \times 0.07 \times 0.1359 = 821.325 \, \text{kg}2,500 m3×0.07×0.1359=821.325kg Rounded to the closest answer: 820 kg In imperial units:
* Net Volume: 88,287 ft³
* S-Factor: 1.885
Calculation:
88,287 ft3×0.07×1.885=1,165.27 lbs88,287 \, \text{ft}^3 \times 0.07 \times 1.885 = 1,165.27 \, \text{lbs}
88,287ft3×0.07×1.885=1,165.27lbs
Rounded, this is approximately 1,800 lbs.
EPI Data Center Specialist References:
EPI instructs on using specific formulas and S-factors provided by manufacturers for each gas type, ensuring that calculations reflect the correct concentration for the given room volume.
質問 # 79
Do you need to consider bullet (ballistics) protection when designing a data center?
- A. Bullet (ballistics) protection is only required when the data center is located in an area with a high crime rate.
- B. Bullet (ballistics) protection is required by ANSI/TIA-942 for all data centers.
- C. Bullet (ballistics) protection is only required if the facility is a potential target or the building is in the vicinity of a potential target.
- D. Bullet (ballistics) protection is required by ANSI/TIA-942 for data centers Rated 3/4.
正解：C
解説：
Bullet (ballistics) protection is typically considered only for data centers that are potential targets or located near such targets. While ANSI/TIA-942 does not specifically require bulletproofing for all data centers, it is prudent to consider it based on location risk assessments, especially if the facility is in a high-risk area or near critical infrastructure that could attract threats.
Detailed Explanation:
Protective measures like bulletproofing depend on the threat landscape and the data center's exposure to risks such as crime or terrorism. Assessments for physical security are typically customized based on location-specific risks rather than being universally required by data center standards.
EPI Data Center Specialist References:
EPI guidelines emphasize customizing physical security measures based on threat assessments, suggesting that bulletproofing is appropriate in specific circumstances where the facility's risk profile justifies additional security measures.
質問 # 80
Which formula is correct?
- A. Phase-to-Neutral Voltage = Phase-to-Neutral voltage * 1.732
- B. Phase-to-Neutral Voltage = Phase-to-Phase voltage * 1.732
- C. Phase-to-Neutral Voltage = Phase-to-Phase voltage /1.732
- D. Phase-to-Neutral Voltage = (Phase-to-Phase voltage * 1.732) / Phase-to-Neutral Voltage
正解：C
解説：
The correct formula for calculating Phase-to-Neutral Voltage in a three-phase power system is Phase-to- Neutral Voltage = Phase-to-Phase Voltage / 1.732. This formula applies to balanced three-phase systems, where 1.732 (or #3) represents the relationship between line-to-line and line-to-neutral voltages.
Detailed Explanation:
In three-phase systems, Phase-to-Phase Voltage is higher than Phase-to-Neutral Voltage by a factor of #3.
Dividing the phase-to-phase voltage by 1.732 gives the phase-to-neutral voltage, which is critical for understanding power distribution in three-phase electrical systems commonly found in data centers.
EPI Data Center Specialist References:
EPI electrical training highlights the importance of knowing these calculations for designing and maintaining balanced power systems, which are essential for stable and efficient data center operations.
質問 # 81
You want to manage temperature and humidity only at the facility level in your data center. All servers use front-to-rear airflow. Which location for measurement should you recommend?
- A. At the front/intake of the server at 50 mm (2 in)
- B. At 1.5 m (5 ft) above the floor, 0.4 m (15 in) at the back of the rack
- C. At the back/rear of the server at 50 mm (2 in)
- D. At 1.5 m (5 ft) above the floor, 0.4 m (15 in) in front of the rack
正解：D
解説：
ASHRAE recommends temperature and humidity be measured in the cold aisle, in front of racks, at approximately 1.5 m above the floor (average human working height) and 0.3-0.5 m from the rack face. This location captures the environmental conditions experienced at the IT equipment air intake, while still representing facility-level conditions (not single device-level).
* Option A and C (at 50 mm intake/rear) are too close to individual servers and suited only for rack-level monitoring, not facility monitoring.
* Option D (rear measurement) reflects exhaust air, not intake, and thus cannot be used to control environmental setpoints.
Maintaining measurement at standardized facility locations allows comparisons against ASHRAE's recommended and allowable ranges (18-27 °C for Class A1 environments, 40-60% RH).
References: ASHRAE TC 9.9 "Thermal Guidelines for Data Processing Environments" (2016), ANSI/TIA-
942-B §6.5.
質問 # 82
Management requests a 15-minute battery bank at full UPS load. UPS specs:
* 30 kVA, PF 0.8
* Battery 384 V (192 cells), end discharge 308 V
* Inverter PF 0.8, 400 V output
What information is missing to perform the calculation?
- A. UPS efficiency
- B. Load imbalance
- C. Available battery charging current
- D. Inverter efficiency / output PF
正解：A
解説：
Battery sizing requires determining the real power demand of the UPS. With 30 kVA at 0.8 PF, the real load is 24 kW. To calculate required ampere-hours for 15 minutes of runtime, we need:
Where P = load, t = runtime, V = battery voltage, and # = UPS efficiency.
Without UPS efficiency, we cannot know actual DC load on the batteries. A UPS with 90% efficiency will require more battery capacity than one with 95%. None of the other listed parameters (PF, imbalance, charging current) are critical for runtime capacity calculation.
References: IEEE Std 1188 (VRLA Batteries), IEC 62040-3 (UPS performance), ANSI/TIA-942-B §6.2.
質問 # 83
The pipes of a VESDA smoke detection system are installed at the air intake of the air conditioner inside the computer room.
Is this a good practice from an early smoke detection point of view?
- A. Yes, as this reduces the amount of piping to be installed in the data center, as all air will go through the air conditioner.
- B. It depends on the type of gas-based fire suppression which will be installed.
- C. No, it will give a longer reaction time for the smoke detection system and there might also be bypass airflow.
- D. No, the piping should be installed at the air exhaust of the air conditioner, as there can also be a fire inside the air conditioner itself.
正解：C
解説：
For optimal early smoke detection in a data center, it is crucial that the Very Early Smoke Detection Apparatus (VESDA) system be installed at locations where smoke will be detected as soon as it appears.
Positioning the VESDA pipes at the air intake of the air conditioner inside the computer room is not ideal.
This placement could result in a delayed detection response and the potential for bypass airflow to occur, which would impede the system's ability to detect smoke effectively.
Detailed Explanation:
When VESDA pipes are installed at the air intake, the detection system relies on the smoke to be drawn into the air conditioning unit before detection can occur. This setup increases the reaction time as the smoke has to travel through the intake and get processed by the air conditioner. Furthermore, bypass airflow-a phenomenon where not all the air containing smoke particles passes through the VESDA pipes-could also delay or even prevent the system from detecting smoke early.
Ideally, VESDA pipes should be positioned where smoke is likely to accumulate first, such as near the ceiling or in the return airflow path to detect smoke at the earliest possible stage. This ensures that the detection system can quickly trigger alarms, providing more time to address potential fire hazards.
EPI Data Center Specialist References:
EPI Data Center Specialist training highlights that smoke detection should prioritize early response capabilities to maximize safety. The preferred installation for VESDA pipes is generally at points where smoke would naturally accumulate, rather than relying on air conditioning intakes where airflow can vary and delay detection. In their course materials, EPI emphasizes minimizing reaction time and reducing the impact of airflow dynamics on smoke detection efficiency.
質問 # 84
It is assumed that EMF shielding material must be installed as the EMF levels coming from the transformer room into the computer room are measured at 100mG. The transformer room is approximately 10 meters away from the computer room and is separated by a corridor. You can assume that no physical issues are present for installing shielding material at any area/location.
Where should you recommend the shielding material to be installed?
- A. It does not matter, either close to the transformer room or the computer room is okay as there is no impact to cost or shielding material performance
- B. As close as possible to the computer room
- C. Shielding is not required to be installed as 100mG is within the acceptable levels for computer rooms
- D. As close as possible to the transformer room
正解：D
解説：
EMF shielding is most effective when installed close to the source of the EMF, which in this case is the transformer room. Shielding at the source contains the magnetic fields before they spread, minimizing exposure throughout the facility, including the computer room.
Detailed Explanation:
Placing shielding close to the EMF source minimizes the area impacted by electromagnetic interference, as it reduces the distance over which the EMF can spread. Shielding materials near the source can absorb or redirect EMF, providing the most effective reduction of EMF levels in adjacent spaces, like the data center.
EPI Data Center Specialist References:
EPI data center training advises positioning shielding close to the EMF source to contain fields more effectively and reduce interference in critical areas. This method is more efficient and cost-effective, as it limits the spread of EMF from the point of origin.
質問 # 85
What indicates the overcurrent of a fuse or breaker?
- A. The current that a fuse or breaker is able to interrupt without being destroyed or causing an electrically damaging arc
- B. The current at which the device will trip
- C. The maximum electrical current which can flow in a particular electrical system under short-circuit conditions; it is determined by the voltage and impedance of the supply system
- D. The maximum inrush current an overcurrent protection device can handle within a defined period of time
正解：B
解説：
"Overcurrent" for protective devices is the condition above the device's rated/trip value that causes operation (tripping/melting).
* A = inrush tolerance, not the definition of overcurrent.
* B = prospective short-circuit current (Ik).
References: IEC 60947-2 (LV circuit breakers, defs 2.5.13 Overcurrent; 2.3.3 Rated short-circuit breaking capacity), IEC 60269 (fuses).
質問 # 86
What is the risk of high levels of hydrogen sulfide (H#S) in the computer room?
- A. H#S can cause corrosion which impacts reliability of equipment
- B. H#S impacts the static properties of the floor
- C. There is no risk
- D. H#S impacts gas-based fire suppression system operation
正解：A
解説：
Hydrogen sulfide (H#S) is a corrosive gas that readily reacts with metals, especially copper and silver found in circuit boards, connectors, and power supply components. Even at concentrations below human detection thresholds, H#S can cause sulfidation corrosion leading to intermittent connections, failure of solder joints, and increased failure rates of electronic equipment.
ASHRAE Technical Committee 9.9 has documented multiple failures in data centers due to corrosive gases (notably sulfur-bearing compounds). Therefore, high humidity combined with H#S presence accelerates this risk.
H#S does not affect static flooring properties (B) or fire suppression agent chemistry (D). Option A is clearly incorrect as the risk is well-documented.
References: ASHRAE TC 9.9 "Particulate and Gaseous Contamination Guidelines" (2011), IEC 60721-3 (Environmental Classification).
質問 # 87
A computer room needs to be fitted out with a gas-based fire suppression system. The computer room will be a high-density data center with about 30% of the racks being closed circuit cooling blade-center racks.
Should the supplier of the fire suppression system be informed on the design of the racks?
- A. Only when the rack height obstructs a potential fire suppression release point.
- B. Yes, the design of the racks has an influence on the fire suppression system design.
- C. No, cooling and design of racks have no influence on the fire suppression system design.
- D. Only when the racks might block access to the fire panel.
正解：B
解説：
The design and configuration of racks, particularly high-density and closed-circuit cooling racks, directly impact the fire suppression system design. Closed-circuit cooling racks, like blade-center racks, can affect airflow and potentially trap heat, influencing how fire suppression agents are distributed within the space.
Therefore, it is essential to inform the fire suppression system supplier about the rack design to ensure effective coverage and proper agent distribution.
Detailed Explanation:
High-density racks can change how smoke and heat travel, which in turn affects fire detection and suppression. Closed racks with built-in cooling can isolate airflow, requiring adjustments in fire suppression design to ensure that suppression agents reach all necessary areas, including within enclosed spaces. The supplier may need to account for these factors to ensure proper protection coverage.
EPI Data Center Specialist References:
The EPI Data Center Specialist training underscores that fire suppression systems must be tailored to the specific environmental characteristics of the data center. The design of racks, particularly high-density configurations, should always be considered to ensure that suppression agents can effectively control a fire, even in contained rack spaces.
質問 # 88
Can you install a raised floor tight to the perimeter of the room?
- A. No, but this applies only to raised floors with a height of over 90 cm (3 ft)
- B. Yes, a raised floor needs to be installed tight to the perimeter to prevent air leakage
- C. No, to avoid damage to the raised floor due to building and hygrothermal movement
- D. Yes, but only if the data center is located in Zone 0 with no or little seismic activity
正解：C
解説：
Raised floors must not be installed flush against perimeter walls. Buildings expand, contract, and shift due to thermal expansion (hygrothermal movement), structural settlement, and seismic activity. If the raised floor is rigidly connected to the walls, this movement transfers directly into the raised floor grid, causing buckling, cracking, or tile misalignment.
Industry standards (e.g., CISCA - Ceilings & Interior Systems Construction Association guidelines) require leaving a small perimeter gap (typically 1-2 cm) between raised floor tiles and walls. This gap is then sealed with flexible firestops or brush gaskets to control air leakage while preserving movement tolerance.
Therefore, the correct practice is to leave a separation space, making answer C correct. Options A and D restrict this requirement incorrectly, while B is factually wrong (sealing against the perimeter is not allowed).
References: CISCA Raised Floor Installation Guidelines, ANSI/TIA-942-B §6.3 (Flooring and Seismic Considerations).
質問 # 89
Which of the following statements is correct?
- A. With voltage decreasing, three-phase cables emit more EMF than single-phase cables
- B. With current increasing, single-phase cables emit more EMF than three-phase cables
- C. With voltage increasing, single-phase cables emit more EMF than three-phase cables
- D. With current decreasing, three-phase cables emit more EMF than single-phase cables
正解：B
解説：
Electromagnetic field (EMF) strength around cables is primarily influenced by current, not voltage. In a single-phase system, the live and neutral conductors are separated, creating a larger magnetic loop area. This produces stronger stray EMF when current increases.
In a balanced three-phase system, the magnetic fields from the three conductors largely cancel each other out, resulting in much lower net EMF, even at higher currents.
Therefore, the correct statement is that increasing current in single-phase cables produces higher EMF compared to three-phase cables. Options B, C, and D incorrectly link EMF to voltage or incorrect current behavior.
References: IEEE Std 141 (Red Book - Power Distribution), IEC 61000-5-7 (EMF mitigation guidelines), ANSI/TIA-942-B §6.6.
質問 # 90
What should be implemented when an Inergen-based fire suppression system is installed in the computer room?
- A. Drainage system under raised floor
- B. Proper water leak detection system
- C. Gas tanks need to be within or close to the data center
- D. Pressure release valves in the data center
正解：D
解説：
Inert gas systems (Inergen, Argonite, Nitrogen) extinguish fires by reducing oxygen concentration through massive gas discharge. This rapid release causes a significant pressure rise inside the room. To avoid structural damage to walls, ceilings, or raised floors, pressure relief vents (pressure release valves) must be installed.
* A (drainage) applies to water suppression.
* B (tank location) is logistical but not mandatory; remote storage with piping is acceptable.
* D (water leak detection) is unrelated to inert gas suppression.
Therefore, the critical safety requirement is pressure relief.
References: NFPA 2001 §5.2.1.2 (Pressure Relief), ISO 14520-1 §5.2.
質問 # 91
A customer requires THDi from the UPS not to exceed 3% and wants high efficiency. The UPS has a 6-pulse SCR/thyristor rectifier and is loaded ~80%. Many ICT changes are expected in the next 3 years. What should you recommend?
- A. Nothing; the UPS will keep THDi at the right levels
- B. Install a passive harmonic filter on the UPS
- C. Install an isolation transformer rated K13 or K20
- D. Install an active harmonic filter on the UPS
正解：D
解説：
A 6-pulse thyristor rectifier typically produces 25-35% THDi at nominal load. To reach #3% THDi, an active harmonic filter (or a 12/18-pulse or IGBT rectifier UPS) is required. Passive filters are load-specific and less effective over a wide operating range-undesirable with frequent changes.
References: IEEE 519-2014 (harmonic current limits), UPS vendor application notes (6-pulse vs IGBT rectifier THDi), ANSI/TIA-942-B Annex (power quality).
質問 # 92
The logical overview of the data center looks as pictured. To what TIA-942 Rating is this design made based on electrical only?
- A. Rating - 2
- B. Rating - 4
- C. Rating - 1
- D. Rating - 3
正解：B
解説：
The electrical design shown in the diagrams represents a TIA-942 Rating-4 configuration. This design includes full redundancy and fault tolerance, as demonstrated by the dual power distribution paths from the utility supply to the critical loads. Each power distribution path is equipped with its own UPS, ensuring that the ICT equipment and mechanical equipment have uninterrupted power in case of any single point of failure.
Detailed Explanation:
A Rating-4 data center requires two independent power paths that are fully redundant and capable of supporting the load independently. In the diagrams:
* There are dual feeds from the utility supply, each going through separate transfer switches and power distribution paths.
* Both paths have backup sources (+1) and serve critical components through separate UPS systems, providing a completely redundant setup.
* The design also includes redundant paths to the mechanical equipment and ICT equipment, which further indicates the fault-tolerant characteristics of a Rating-4 infrastructure.
This setup allows for concurrent maintainability and ensures that no single failure in power distribution or UPS can impact the data center's operation, which is characteristic of the highest Tier/Rated-4 classification.
EPI Data Center Specialist References:
EPI guidelines confirm that TIA-942 Rating-4 requires full redundancy and fault tolerance for electrical infrastructure, ensuring continuous operation even during maintenance or failure events. This design meets all those requirements, thus aligning with Rating-4 standards.
質問 # 93
What is the minimum requirement for the power feeds to the building for a Rated-3 data center based on the ANSI/TIA-942 standard?
- A. Two feeds coming from two different substations, one power company is not acceptable
- B. Two feeds coming from two different substations, one power company is acceptable
- C. One feed from one substation split over two separated distribution boards in separate rooms
- D. Two feeds entering the data center building from one substation
正解：B
解説：
The minimum requirement for power feeds to a Rated-3 data center according to ANSI/TIA-942 is to have two independent power feeds, which can come from two different substations provided by the same power company. This ensures redundancy and concurrent maintainability, as each feed can support the load independently during maintenance or failure of the other.
Detailed Explanation:
The separation by two substations ensures resilience in case of a localized outage or substation maintenance, aligning with Rated-3 requirements for uninterrupted operation. ANSI/TIA-942 permits these feeds from a single utility provider as long as they are supplied from distinct substations.
EPI Data Center Specialist References:
EPI underscores the importance of dual power feeds from separate substations for Rated-3 facilities, highlighting that the ability to draw from different substations aligns with redundancy requirements for high availability.
質問 # 94
A data center scores Rated-3 in mechanical, Rated-4 in electrical, and Rated-2 in telecommunications. What is the overall rating?
- A. Rated-4 since electrical is most important
- B. Rated-4
- C. Rated-2
- D. Depends on architectural rating
正解：C
解説：
ANSI/TIA-942 defines that the lowest rating across all four categories determines the overall facility rating. A facility cannot claim a higher overall level unless all subsystems meet or exceed that level.
In this case:
* Mechanical = Rated-3
* Electrical = Rated-4
* Telecommunications = Rated-2
Since telecommunications only meets Rated-2, the overall facility is Rated-2, regardless of higher scores elsewhere.
This ensures that weak areas (like cabling) are not ignored, because they can compromise overall availability.
References: ANSI/TIA-942-B §5.2.3 (Overall rating determination).
質問 # 95
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