ups专用变压器设计讲解（重温基础开关柜）

ups专用变压器设计讲解（重温基础开关柜）· Learn about basic construction and operation of switchgear transformers and uninterruptible power supplies.· 了解电气开关柜、变压器和不间断电源的基本结构和操作。电气开关柜、电力变压器和UPS是数据中心电力设施中非常重要的设备。本文介绍了这些关键设备的基本组成、工作原理、额定铭牌参数、各类设备的特征和应用场景，以及相关的规范和标准。通过对本文的学习，数据中心设计、施工、运营各方相关技术人员可以快速了解这些电气设备的特性和基础知识，从而加深对数据中心电气设备的理解。学习目标Learning Objectives

重温基础：开关柜、电力变压器和UPS

Back to basics: Switchgear Transformers and UPSs

by TOM DIVINE PE LEED AP- July 29 2020

译 者 说

电气开关柜、电力变压器和UPS是数据中心电力设施中非常重要的设备。本文介绍了这些关键设备的基本组成、工作原理、额定铭牌参数、各类设备的特征和应用场景，以及相关的规范和标准。通过对本文的学习，数据中心设计、施工、运营各方相关技术人员可以快速了解这些电气设备的特性和基础知识，从而加深对数据中心电气设备的理解。

学习目标

Learning Objectives

· 了解电气开关柜、变压器和不间断电源的基本结构和操作。

· Learn about basic construction and operation of switchgear transformers and uninterruptible power supplies.

· 了解这些设备的应用场景。

· Understand the fundamental applications of this equipment.

· 了解这些设备的的相关规范、标准和额定铭牌参数。

· Know the most significant codes standards and ratings applicable to each.

了解电气开关柜、变压器和不间断电源的运行、施工和应用，对于参与设计、项目预算和设备布局评估的设计人员、规范编制人员、设施运营方和施工经理来说非常重要。

An understanding of the operation construction and application of operation of switchgear transformers and uninterruptible power supplies is important for designers specifiers facility owners and construction managers who may be called on to render decisions about design project budgets and available space.

开关柜

Switchgear

电气开关柜是一种配电设备：它将一个电源分配到多个输出回路，并提供过电流保护和控制功能。在NFPA 70《国家电气规范》第408条：开关柜和配电柜中描述的配电设备类型中，开关柜通常是结构最坚固、体积最大和最昂贵的。它通常应用于医院或数据中心等高可靠性设施，在这些设施中，电源的连续性对有效运行至关重要。Switchgear is electrical distribution equipment: it accepts power from a source routes it to a number of outputs and provides overcurrent protection and control functions. Of the types of distribution equipment described in the NFPA 70: National Electrical Code Article 408: Switchboards Switchgear and Panelboards switchgear is generally the most robustly constructed the largest and the most expensive. It’s typically applied in high-reliability facilities like hospitals or data centers where continuity of power is critical to effective operation.

图1：用于发电机并机的大型开关柜。提供：约翰斯顿有限责任公司

Figure 1: A large switchgear lineup is used for paralleling generators. Courtesy: Johnston LLC

开关柜的额定电压范围从1000伏以下到200千伏以上。额定电压高于1000伏的中压开关柜有多种配置，采用壁挂式安装、吊顶式安装或安装在专用的独立式金属框架中，并使用空气、气体、真空或油作为绝缘介质。本文将重点讨论户内式低压开关柜。Switchgear is available in a wide range of voltage ratings from below 1 000 volts to more than 200 kilovolts. Medium-voltage switchgear rated above 1 000 volts is manufactured in a variety of configurations. Assemblies are available for exterior padmount installation vault installation or installed in dedicated freestanding metal buildings with air gas vacuum or oil as insulating media. This discussion will focus on interior low-voltage switchgear.

开关柜的替代品是配电柜。配电柜通常只需更少的空间，也更便宜。这两者通常由多个垂直部分构成，其中每个部分都用金属隔板封闭并为过电流保护装置、监控设备和控制装置设计了开孔，其余部分还包含一个主过电流保护装置、计量装置、自动控制和监控系统、馈线过电流保护装置及其组合，亦或选用其他特定设备的组合。目前过流保护装置已经很少选用带熔丝的刀闸开关，通常选用带过流保护功能的断路器。The alternative to switchgear is switchboard construction. Switchboards generally require less space and are less expensive. Both are typically constructed of a number of vertical sections. Each section is enclosed in sheet metal with openings in front for overcurrent protection devices monitoring equipment and control devices. A section may contain a main overcurrent protection device metering devices automatic control and monitoring systems overcurrent protection devices for distribution feeders or a combination of these or other equipment specific to the installation. Overcurrent protection is typically accomplished with circuit breakers with fused switches are less frequently.

低压开关柜按照UL 1558《金属封闭低压电力断路器开关设备标准》制造。配电柜按照UL 891《配电柜标准》制造。与UL 891相比，UL 1558包含了许多提高可靠性、耐久性和可维护性的要求。

LV switchgear is constructed to UL 1558: Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear. Switchboards are constructed under UL 891: Switchboards. UL 1558 incorporates a number of requirements that enhance the reliability durability and maintainability over UL 891.

开关柜断路器通常采用四位垂直层叠式单独安装方式，且每个断路器与其他断路器都完全隔开。在典型的开关柜设计中，水平和垂直母线封闭在断路器隔间后的母线隔间中，该母线隔间使用绝缘隔断与柜内其余部分完全隔开。

Switchgear breakers are typically installed four high in a vertical section individually mounted. Each circuit breaker is separated by solid barriers from other breakers and from the rest of the assembly. In a typical switchgear assembly the horizontal and vertical buses are enclosed in a bus compartment to the rear of the breaker compartments and this bus compartment is isolated from the rest of the assembly using insulating barriers.

电缆端接排位于配电柜的后部隔间，通过绝缘隔板和母线隔间完全分隔开。根据UL 891标准，配电柜不需要在组件之间提供相同级别的隔离。但UL 1558规定，为了避免维修人员在安装或维护期时接触到相邻断路器的导电部分，提高开关柜的可靠性和可维护性，需要设置这些隔间和隔板。当短路故障产生电弧时，这也将相邻部件的损坏降到最低。

Finally the cable conNECtions are in the rear compartment which is isolated from the bus compartment with an insulating barrier. These separations and barriers prescribed by UL 1558 are intended to increase the reliability and maintainability of switchgear by limiting the possibility of contact between conductors attached to adjacent breakers during installations or maintenance and to minimize any damage to adjacent components in the event that an arcing fault should develop.Switchboards under UL 891 are not required to provide the same level of isolation between components.

图2：已安装断路器的开关柜简化剖面图，图中展示了断路器室、垂直母线隔间和电缆连接隔间。提供：约翰斯顿有限责任公司

Figure 2: This simplified section view of an installed switchgear breaker shows the breaker compartment vertical bus and cable connections. Courtesy: Johnston LLC

低压开关柜中安装的断路器必须符合UL 1066《配电柜箱体中的低压交流和直流断路器标准》的要求。本标准要求断路器具有30周波的耐压值，和承受0.5秒而不损坏的故障电流等级，且具备瞬时或延时跳闸功能。通过设置合适的过电流保护设定值，使得下游断路器动作，断开故障点，而不会造成上游断路器越级跳闸。

Circuit breakers installed in LV switchgear are required to meet UL 1066: Standard for Low-Voltage AC and DC Power Circuit Breakers Used in Enclosures. This standard requires that circuit breakers have a 30-cycle withstand rating describing the level of fault current that they can tolerate for 0.5 seconds without damage. The instantaneous trip function can thus be delayed to allow downstream breakers to clear a fault without tripping the switchgear breaker facilitating selective coordination.

配电柜制造需要遵循UL 489《塑壳断路器、塑壳开关和断路器外壳》标准。按照本标准制造的断路器只需具有3个周期的耐受时间，即0.05秒（3´1/60Hz）。对于这些断路器，只具备瞬时过流跳闸功能，不带延迟过流跳闸功能，也可使用带熔丝的刀闸。封闭式开关的适用标准为NEMA KS1《重载外壳防护封闭式开关》。

The switchboard standard allows breakers built to UL 489: Molded-Case Circuit Breakers Molded-Case Switches and Circuit-Breaker Enclosures. Breakers built to this standard are required only to have a 3-cycle withstand 0.05 seconds. For these breakers the instantaneous trip function cannot be delayed to facilitate selective coordination. Use of fused switches is also allowed. The applicable standard for enclosed switches is NEMA KS1: Heavy Duty Enclosed and Dead-Front Switches.

开关柜额定铭牌参数包括：

Switchgear ratings include:

绝缘水平

Insulation level

最大持续电流

Maximum continuous current

最大电压

Maximum voltage

电源频率

Power frequency

短路耐受电流

Short-circuit withstand current

短时耐受电流（热稳定电流）

Short time withstand current

在典型安装中，低压开关柜连接到厂用变压器或设施变压器的二次侧。采用中压供电方式时，电力变压器可与开关柜用螺栓固定在一起，形成一个单元。由此产生的组件称为“模块化变电站”。开关柜的馈线断路器通常为大型设施负载（如冷机、大型变压器或大型UPS）或其他配电设备供电，包括低压配电柜、电机控制中心、配电箱或其他开关设备组件等。

In a typical installation LV switchgear is connected to the secondary of a power transformer — either the utility’s service transformer or a facility transformer. Where service is at medium voltage a power transformer may be close-coupled to the switchgear with the two assemblies bolted together to form a single unit. The resulting assembly is called a “unit substation.” The distribution breakers of the switchgear will typically serve feeders to large facility loads such as chillers large transformers or large UPSs — or other distribution equipment such as switchboards motor control centers panelboards or rarely other switchgear assemblies.

电力变压器

Transformers

在可靠性和可维护性方面，开关柜比配电柜结构具有明显的优势。在一个特定项目上使用哪种类型取决于多种因素。配电柜只需相当小的占地面积，即可提供相同的配电和保护功能，因此可用空间将决定是否选择配电柜。而开关柜的价格要高得多，投资成本比配电柜高约60%至100%。因此，如果项目预算紧张，就偏向选用配电柜。而且，在需要采取过流保护选择性协调的项目中，尤其是在NEC第700.28条要求严格协调的应急系统上，就只能选开关柜作为解决方案。

Switchgear has definite advantages over switchboard construction in terms of reliability and maintainability. The decision of which system to use on a particular project will depend on a variety of factors. Switchboard construction requires a considerably smaller footprint to provide the same distribution and protection functions so available space will have an impact on the selection. Switchgear is considerably more expensive with a cost penalty on the order of 60% to 100% so a tight project budget will bias the decision toward switchboard constructions. And in projects where selective coordination is challenging particularly on an emergency system where strict coordination is required by NEC Article 700.28 switchgear may be the necessary solution.

变压器是一种交流电磁装置，通过磁场将电能从一个或多个一次绕组回路传输到一个或多个二次绕组回路。一次绕组回路和二次绕组回路通常运行不同的电压和电流，它们之间的比率由变压器的特性决定。NEC《国家电气规范》第450条描述了变压器的相关要求。

A transformer is an alternating-current electromagnetic device that magnetically moves power from one or more primary circuits to one or more secondary circuits. The primary and secondary circuits secondary circuits typically operate different voltages and currents with the ratio between them determined by the transformer’s characteristics. Requirements for transformers are described in NEC Article 450.

变压器在现代生活中无处不在，它具有各种不同的特性、额定值和用途。在高功率应用场合，电力公司使用大型电力变压器连接不同电压等级的输电系统。在小型终端，微型信号变压器被用于将通信设备连接到以太网系统，微型变压器甚至被印刷在集成电路中。而设施配电系统中使用的变压器介于这两个极端应用场合之间。Transformers are ubiquitous in modern life with a variety of characteristics ratings and uses. On the high-power end of the scale electric utilities use large power transformers to connect transmission systems operating at different voltages. On the small end tiny signal transformers are used to connect communication equipment to Ethernet systems and microscopic transformers have even been printed in integrated circuits. Transformers used in facility distribution systems fall between those extremes.

变压器的工作原理是磁感应。这是一种电磁原理，即导体在周围磁场变化的情况下，导体两端会产生电压。磁感应是19世纪由一些科学家发现并量化的，他们的贡献如此重大，以至于电学测量单位和物理学定律都用他们的名字来命名。由于篇幅限制，下文描述变压器运行原理时，我们再简单地讲讲磁感应的原理。

A transformer operates on the principle of magnetic induction an electromagnetic principle that states that a voltage will develop across a conductor in the presence of a changing magnetic field. Magnetic induction was discovered and quantified in the 19th century by scientists whose contributions were so significant that their names have been attached to electrical units of measure and laws of physics. A thorough treatment of magnetic induction would require many times the space available here so it will be treated qualitatively in this discussion of transformer operation.

一个简单的变压器可能由一个称为“铁芯”的铁环组成，一个一次线圈和一个二次线圈分别围绕该铁环形成的回路，称为“绕组”，如图3所示。当交流电流过一次绕组时，其产生的磁场大小和方向随输入功率而变化。

In an elementary implementations a simple transformer might consist of an iron ring called the “core ” with one primary and one secondary each making multiple loops around the ring called “coils ” as shown in Figure 3. When the primary is energized with alternating current the primary coil generates a magnetic field that varies in magnitude and direction with the input power.

图3：单相变压器线圈回路示意图。提供：约翰斯顿有限责任公司

Figure 3: A simplified diagram shows a single-phase transformer coil. Courtesy: Johnston LLC

从理论上讲，整个变压器空间都有磁场，但铁芯的磁特性将几乎所有磁场都集中在环体内，在环体内，磁场同时通过一次绕组和二次绕组。流经二次绕组的时变磁场通过磁感应产生出感应电压。一次绕组数和二次绕组数的商称为“匝数比”，其中匝数指的是绕铁芯的导线匝数。最后得知，二次电压等于一次电压除以匝数比。

In theory that magnetic field exists throughout all space but the magnetic characteristics of the iron core concentrate nearly all of the magnetic field within the body of the ring where it passes through both the primary and secondary coils. The time-varying magnetic field running through the secondary coil induces a voltage across those coils by magnetic induction. The quotient of the number of primary loops and the number of secondary loops is called the “turns ratio ” where turns refers to turns of wire around the core. In the end the secondary voltage is equal to the primary voltage divided by the turns ratio.

真实的变压器比这里描述的原理模型要复杂得多。例如，设施中安装的大多数变压器都是三相装置，其铁芯几何结构必须容纳三个一次线圈和三个二次线圈。变压器通常在二次线圈上配备分接头，在系统负载、市电电压或其他原因导致电压长期低于或高于正常值的应用场合，可以通过分接头将输出电压调整至略高于或低于铭牌额定电压。变压器铁芯通常由特殊钢板制成，用绝缘粘合剂粘合在一起，而不是用实心铁或钢，以减少铁芯在运行时的涡流。典型的设施变压器安装在金属外壳内，通常带有通风孔。

Real-world transformers are much more complex than the naïve implementation described here. For example most transformers installed in facilities are three-phase units whose core geometry must accommodate three primary and three secondary coils. Transformers are often provided with taps on the secondary coil — additional connection points whose output voltage is slightly higher or lower than the nominal voltage for use in applications where voltages lower or higher than normal chronically occur due to system loading utility voltage levels or for other reasons. Transformer cores are typically made from sheets of specialty steel bonded together with an insulating adhesive rather than solid iron or steel to reduced magnetically induced currents that circulate in the core during operation. A typical facility transformer is mounted inside a metal enclosure usually with openings for ventilation.

变压器的一次绕组和二次绕组之间没有电的连系。一二次绕组之间的磁场使得二次绕组输出电压达到特定值。但理论上，绕组导体与其周围环境之间的电压尚未定义。对于大多数系统，其中一根二次绕组导线必须有意接地，以确保二次导线上的电压不会偏离地电位太远。但这个规则并不适用于能够容忍单点接地故障的系统，例如医疗设施中的隔离电源系统。

No conductive connection exists between the primary and secondary coils of a transformer. The magnetic interaction between the coils forces the voltage between the secondary conductors to a specific value but the voltage between either conductor and its surroundings is in theory undefined. For most systems one of the secondary conductors must be intentionally connected to ground to ensure that the voltage on the secondary doesn’t stray too far from earth potential. Exceptions to that rule are systems that must be tolerant of a single ground fault such as isolated power systems in medical facilities.

图4：安装在操作间里的一个隔离的配电柜，柜内正下方为隔离变压器。

Figure 4: An isolated power panel is installed in an operating room.

The transformer is visible at the bottom of the enclosure. Courtesy: Johnston LLC

变压器额定铭牌参数包括：

Transformer ratings include:

容量，通常以千伏安表示，即变压器可向其负载提供的最大视在功率。

Capacity typically expressed in kilovolt amperes the maximum apparent power that the transformer can supply to its loads.

一次电压或线路电压——一次绕组的工作电压。

Primary voltage or line voltage — the operating voltage of the primary coil.

二次电压或负载电压——二次绕组的工作电压。

Secondary voltage or load voltage — the operating voltage of the secondary coil.

温升（单位：摄氏度）——变压器满载运行时，变压器线圈温度与环境温度之间的差值。

Temperature rise typically expressed in degrees Celsius — the difference between the temperature of the transformer coils and ambient temperature when the transformer operates at full load.

规范中通常出现的变压器的其他特征包括相数、变压器抽头的数量和电压调节范围、外壳防护等级、绝缘介质、阻抗和效率。Other features of transformers that normally appear in specifications are number of phases number and spacing of transformer taps enclosure characteristics insulation medium impedance and efficiency.

变压器的效率不是100%。虽然大部分电能都能从一次绕组输送到二次绕组，但有些功率会因热量而损失，这些损耗可以被描述为负载损耗（铜损--主要是由于线圈导体的电阻导致的损耗）以及空载损耗（铁损--主要是由于铁芯内外的磁效应导致的损耗）。这两种类型的损失是相互依存的，因为设计减少一种类型的损失就会提高另一种类型的损失。

Transformers are not 100% efficient. While most of the input power is delivered to the secondary terminals some is lost as heat. These losses can be characterized as load losses primarily due to resistance of the coil conductors and no-load losses primarily due to magnetic effects inside and outside of the core. These two types of losses are interdependent in that designing to reduce one type of losses can raise the other.

例如，可以使用大尺寸导线来制造线圈，降低其串联电阻从而降低负载损耗（铜损）。然而，远离铁芯的外层的大尺寸的导体会降低线圈和铁芯之间的磁耦合效率，并提高空载损耗（铁损）。对于大多数变压器，美国能源部的规定描述了所需的效率水平，并规定变压器效率将在35%或接近35%的负载水平下进行优化。这就意味着需要权衡考量变压器的负载损耗和空载损耗。

For example load losses can be reduced by constructing the coils from larger wire reducing their series resistance. However larger conductors will place outside layers further from the core reducing the effectiveness of magnetic coupling between the coil and core and raising no-load losses. For most transformers Department of Energy rules describe required efficiency levels and specify that transformer efficiency will be optimized at a load level at or near 35%. Those regulations generally dictate what trade-offs are between load losses and no-load losses are permissible.

不间断电源

Uninterruptible power supplies

UPS是一种电气设备，它可以连续提供近乎完美的交流电源，电气可靠性接近100%。UPS通常用于支持关键负载。UPS既可为数百伏安的桌面用电设备供电，也可以为额定功率为数千千瓦的大型企业系统供电。

A UPS is an electrical assembly that is designed to provide nearly perfect alternating current power continuously with nearly 100% reliability. A UPS is typically deployed to support electrical loads that are critical to the business conducted in a facility. UPSs are available in very small desktop units to power loads in hundreds of volt-amperes to very large enterprise systems rated in thousands of kilowatts.

UPS的功能是在主进线电源（通常是电力设施）出现断电故障或供电质量超过允许范围时，为其负载提供高质量的电源。UPS在停电、低电压、电压骤降和骤升、单相断电和其他系统干扰期间维持其负载的供电，防止断电和损坏。

The function of a UPS is to provide high-quality power to its load when the primary power source usually an electric utility fails or becomes unacceptable. A UPS maintains power to its load during blackouts brownouts voltage sags and swells loss of a single phase and other system disturbances protecting from both loss of power and from damage.

所有UPS都包含一个储能系统，通常配备化学电池（铅酸、镍镉、锂离子）储能。当输入电源发生故障时，UPS从电池中提取能量，将其转换为交流电并将其输送至负载。目前已有多种UPS拓扑类型得到广泛地应用。

All UPSs contain an energy storage system most often in the form of chemical batteries (lead-acid nickel-cadmium lithium-ion). When the input power fails a UPS draws energy from its batteries converts it to AC and delivers it to the load. A number of schemes for providing replacement power called “topologies ” are in common use.

“双变换”UPS，也称为在线式UPS，内部整流器将输入的交流连续转换为直流电。产生的直流电通过内部逆变器为负载产生交流电源，并维持系统电池的充电。如果交流输入中断，电池将向直流母线供电，并继续转换为交流电源，持续不断地向负载供电。

A “double-conversion” UPS also called an online UPS continuously converts incoming AC to direct current using an internal rectifier. The resulting DC power is used to generate AC power for the load using an internal inverter and to maintain the charge on the system batteries. Should the AC input be disrupted the batteries provide power to the DC bus and the conversion to AC and delivery to the load continue without interruption.

术语“双变换”指的是UPS连续地将交流转换为直流，然后将该直流转换回交流。在这种拓扑类型中，输出交流电的质量不取决于输入电源的质量，因为输出的交流电是由独立的直流总线逆变产生出来的。由于电能转换是连续的，输入侧电源扰动不会影响负载连续用电。这种拓扑类型被认为是高度可靠的。它通常也比其他拓扑类型价格更昂贵、效率更低。

The term “double-conversion” refers to the fact that the UPS continuously converts AC to DC and then converts that DC back to AC. With this scheme the quality of the output AC does not depend on the quality of the input power since the output is independently generated from the DC bus. Because conversion is continuous there is no requirement for detection of input power disturbances in order to protect the load. This topology is seen as highly reliable. It is also generally more expensive and less efficient than the alternatives.

由于双变换UPS持续产生输出交流电，UPS内部故障可能会使关键负载的电源连续性面临风险。为了解决这个漏洞，UPS内置了一个静态开关——一个连接在输入和输出之间的高速电子开关——将输入电源直接连接到负载。UPS监控其自身的输出，如果输出超出可接受的限制，UPS将关闭静态开关并与负载断开。

Because a double-conversion UPS continuously generates the output AC a failure inside the UPS can put the continuity of power to the critical load at risk. To address this vulnerability these units typically include a static switch — a high-speed electronic switch connected between input and output — that will connect the input power directly to the load. The UPS monitors its own output and should the output fall out of acceptable limits the UPS closes the static switch and disconnects itself from the load.

图5：双转换不间断电源原理图。提供：约翰斯顿有限责任公司

Figure 5: A block diagram of a double-conversion uninterruptible power supply is shown. Courtesy: Johnston LLC

“单变换”或“备用”拓扑类型的UPS连续将其输入功率直接传递给负载，而输入是可接受的。UPS监控输入电源是否存在干扰，如果出现任何干扰，UPS会断开输入电源，并开始通过逆变器从电池中为负载供电。该过程需要在输入干扰和更换电源之间进行延迟，以便检测、重新校准系统并启动逆变器。因此，备用UPS适用于系统干扰容限较高的负载。虽然这种拓扑类型不如“双变换”可靠。然而，它的效率更高，因为在正常运行时，它的整流器或逆变器不会出现损耗。

A “single-conversion” or “standby” UPS continuously passes its input power directly to the load while the input is acceptable. The UPS monitors the input power for disturbances and should any appear it disconnects input power and begins to serve the load from its batteries through its inverter. This process necessitates a delay between the input disturbance and the commencement of replacement power for detection realignment of the system and starting the inverter. A standby UPS is therefore applicable to loads with a higher tolerance for system disturbances. This topology is seen as less reliable than double conversion. It is however more efficient since it doesn’t incur losses in its rectifier or its inverter in normal operation.

不间断电源系统额定铭牌参数包括：

Ratings for uninterruptible power systems include:

满载运行时间——用于设计电池容量

Full load runtime — a function of the battery capacity

输入电压

Input voltage

最大输出视在功率，以伏安表示

Maximum output apparent power expressed in volt-amperes

最大输出瓦数，以瓦为单位

Maximum output wattage expressed in watts

输出电压

Output voltages

UPS功率通常按照整个生命周期中预期最大负载的125%进行选择。数据中心需要根据业务发展估算负载的急剧增长，而这种增长有时无法实现，从而浪费了UPS过剩的容量。为了解决这个问题，一些系统提供了模块化的、可热插拔的电源和电池模块，以便随着负载的增加进行扩容和增加持续供电时间。

A UPS is typically sized at about 125% of its expected maximum load estimated for its entire life cycle. Data center applications call for estimates of aggressive load growth that sometimes don’t materialize stranding excess capacity. To address this issue some systems are available with modular hot-swappable power supply and battery modules to allow incremental capacity and runtime upgrades as load increases.

不间断电源需要日常维护，与其他所有设备一样，在使用过程中，它们有时也会出现故障。对于某些系统，将负载直接连接到市电的外部维护旁路是维护和维修活动的充分条件。更敏感的系统需要一定程度的冗余。不间断电源模块可以并联或串联，以提供冗余容量，并在冗余单元之间进行通信和监控。

UPSs require routine maintenance and like everything else they sometimes fail in service. For some systems a wrap-around maintenance bypass connecting the load directly to utility power is an adequate provision for maintenance and repair activities. More sensitive systems will require a level of redundancy. Units can be connected in parallel or in series to provide redundant capacity with communication and monitoring among redundant units.

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翻译：

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iCloud乌兰察布数据中心站点经理

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