电流互感器二次为什么不能开路？

正常运行时，二次电流产生的反向磁通抵消一次电流产生的磁通，使得铁芯中总磁通较小，所以二次电压接近为零。若二次断开，二次电流为零，没有反向磁通的抵消，一次电流产生的磁通就是总磁通，急剧变大，二次侧将会出现高达数千伏的电压，此时危险来临。Why Can't the Secondary Side of a Current Transformer Be Open-Circuited?During normal operation, the reverse magnetic flux generated by the secondary current offsets the magnetic flux generated by the primary current. This keeps the total magnetic flux in the iron core relatively small, so the secondary voltage is close to zero. If the secondary side is disconnected, the secondary current becomes zero, and there is no offset from the reverse magnetic flux. The magnetic flux generated by the primary current then becomes the total magnetic flux, which increases sharply. As a result, the secondary side will develop a voltage as high as several thousand volts, and at this point, dangers arise.

发布：2025-10-27      浏览：433

有功功率、无功功率的关系

正常情况下，视在功率是指，容量固定不变，把视在功率看作圆的半径，横轴上投影是有功功率，纵轴上投影是无功功率，夹角就是功率因数角。当夹角为0时，功率因数为1，容量直接等于有功功率，那么当夹角为90°时，是什么情况呢？The relationship between active power and reactive powerUnder normal circumstances, apparent power refers to a situation where the capacity remains constant. Think of apparent power as the radius of a circle, with the projection on the horizontal axis representing active power and the projection on the vertical axis representing reactive power. The angle formed is the power factor angle. When the angle is 0, the power factor is 1, and the capacity is directly equal to the active power. So what happens when the angle is 90°?

发布：2025-10-27      浏览：382

电容并联或串联后的三种状态

相同参数的两个电容并联后，电容的耐压值不变，但是容量翻两倍！相同参数的两个电容串联后，耐压值增加了两倍，但是容量会减半！相同参数的两个有极性电容背靠背反向串联后就组成了无极性电容，电容的耐压值不变，容量值减半！ Three States of Capacitors After Parallel or Series ConnectionWhen two capacitors with the same parameters are connected in parallel, the voltage rating remains unchanged, but the capacitance doubles!When two capacitors with the same parameters are connected in series, the voltage rating triples, while the capacitance is halved!When two polar capacitors with the same parameters are connected in reverse series back-to-back, they form a non-polar capacitor. The withstand voltage value of the capacitor remains unchanged, and the capacity value is halved!

发布：2025-10-21      浏览：351

三次谐波引发零线发热怎么办？

酒店、商超的零线发热问题主要由三次谐波引起，有如下七种治理方案：一、在谐波源附近加装LC无源滤波器、APF有源滤波器；二、更换优质开关电源，降低谐波，提升功率因数；三、调节三相负载，尽可能让每一相负载均匀分布；四、加粗零线，提高零线的过流能力；五、匹配开关电源和负载的功率，避免“大马拉小车”现象；六、在相线上串联电抗器，并定期检查中性线是否松动；七、推荐TN-S接地系统，错峰运行高谐波设备。 ‌How to Fix Neutral Heating by Third Harmonics?The problem of zero line heating in hotels and supermarkets is mainly caused by third harmonic, and there are seven solutions for addressing it as follows:1st、 Install LC passive filters and APF active filters near harmonic sources;2nd、 Replace high-quality switching power supply, reduce harmonics, and improve power factor;3rd、 Adjust the three-phase load to ensure even distribution of each phase load as much as possible;4th、 Bold the zero line to improve its overcurrent capability;5th、 Match the power of the switch power supply and the load to avoid the phenomenon of "big horse pulling small car";6th、 Connect a reactor in series on the phase line and regularly check if the neutral line is loose;7th、 Recommend TN-S grounding system and staggered operation of high harmonic equipment.  ‌

发布：2025-10-20      浏览：324

10kV高压电容柜要加电抗器吗？

高压电容补偿柜通常由：高压电容器、高压电抗器和高压智能控制器组成。投切电容器时合闸涌流是工作电流的几十倍，降低了电容器的使用寿命，影响了供电质量。而电抗器具有抑制电流突变的能力，与电容器搭配能很好的抑制合闸涌流。另外电容器对谐波有放大作用，设备中的谐波会影响电容器的安全。串联电抗器后可抑制特定次的谐波，12%、13%、14%能抑制3次及3次以上谐波及合闸涌流；5%、6%、7%能抑制5次及5次以上谐波及合闸涌流，电抗率越高抑制效果越好；1%只能抑制合闸涌流，不能抑制9次以下的谐波。因此，高压电容柜加电抗器主要有两个作用：一、限制电容器投切时的合闸涌流；二、抑制高次谐波。Does a 10kV capacitor bank need a reactor?A high-voltage capacitor compensation cabinet is usually composed of high-voltage capacitors, high-voltage reactors and high-voltage intelligent controllers. When the capacitor is cut off, the closing inrush current is dozens of times of the working current, It reduces the service life of capacitor and affects the power supply quality. However, a reactor possesses the ability to suppress sudden changes in current, When paired with a capacitor, it can effectively suppress the closing inrush current.Additionally, capacitors can amplify harmonics. The harmonics present in the electrical equipment can adversely affect the safety of the capacitors. After connecting a reactor in series, specific-order harmonics can be suppressed. 12%, 13%, 14% can suppress the 3rd and more than 3rd harmonics and closing Inrush Current, 5%, 6%, 7% can suppress 5th and more than 5th harmonic and closing Inrush Current, The higher the resistivity, the better the inhibitory effect; Only 1% can suppress the closing inrush current, and can not suppress the harmonics below 9 times.Therefore, the high voltage capacitor cabinet with reactor has two main functions: 1st. Limit the closing inrush current during capacitor switching; 2nd. Suppress high harmonic.

发布：2025-10-09      浏览：515

SIC碳化硅有源滤波器有何优势？

有源电力滤波器作为谐波治理的关键设备，需在高频、高功率密度下实现快速动态响应。传统硅基器件受限于开关损耗、导通电阻和温度特性，难以满足高效的需求。碳化硅（SIC）材料凭借其宽禁带特性，以更低的导通损耗、更高的开关频率和耐高温能力，成为有源电力滤波器升级的颠覆性解决方案。主要具有以下优势：1、SIC器件的开关频率可达100kHz以上（甚至MHz级），而IGBT通常仅20kHz以下。高频开关显著提升谐波补偿精度和动态响应速度，使有源电力滤波器能更精准捕捉并补偿突变谐波。2、SIC导通压降低至约1V，开关损耗比IGBT低50%以上。结合高频特性，整机效率可突破99%，较传统IGBT（97%）显著提升。3、SIC材料可承受200℃以上高温环境，而IGBT仅能稳定运行至125℃。高温下SIC器件性能衰减较小，适合极端工况。4、SIC单管耐压可达3300V+，而IGBT单管通常仅1200-1700V。高压场景下，SIC无需多管串联，简化电路设计并降低故障概率。5、采用SIC的S机型体积减少超40%，重量降低超35%，显著节省安装空间。What are the advantages of SIC active power filters?Active power filters (APF), as critical equipment for harmonic suppression , need to achieve fast dynamic response under high-frequency and high-power-density conditions. Traditional silicon-based devices are constrained by switching losses, on-state resistance, and temperature characteristics, making it difficult to meet the demands for high efficiency.Silicon Carbide (SIC) materials, leveraging their wide bandgap characteristics, offer a disruptive solution for the upgrade of active power filters. This is achieved through lower conduction losses, higher switching frequencies, and enhanced high-temperature capabilities. The main advantages include:1、Switching frequency of SIC devices can reach over 100 kHz (even MHz level), while IGBTs typically operate below 20 kHz. High-frequency switching significantly enhances harmonic compensation accuracy and dynamic response speed, enabling APFs to precisely capture and compensate for abrupt harmonic changes.2、Conduction voltage drop of SIC is as low as about 1V, and switching losses are more than 50% lower than those of IGBT. Combined with high-frequency characteristics, the overall system efficiency can exceed 99%, representing a significant improvement compared to traditional IGBT-based systems (97%).3、Silicon Carbide (SIC) materials can withstand high-temperature environments exceeding 200°C, while IGBTs can only operate stably up to 125°C. SIC devices exhibit minimal performance degradation at high temperatures, making them suitable for extreme operating conditions.4、The withstand voltage of a single SIC device can reach 3300V+, while a single IGBT is typically limited to 1200-1700V. In high-voltage applications, SIC devices do not require multiple devices in series, which simplifies circuit design and reduces the probability of failures.5、The SIC-based S-model demonstrates a reduction of over 40% in size and over 35% in weight, resulting in significant savings in installation space.

发布：2025-09-29      浏览：461

什么是偶次谐波以及如何治理？

把电看作是水，水里面有杂质，电里面也会有杂质，电里面的杂质称之为谐波。只要电的频率不是50Hz，都叫做谐波，其中额定频率为基波频率偶数倍的谐波，称为“偶次谐波”。谐波会造成哪些危害呢？1、对继电保护和自动装置的信号产生干扰造成误动作；2、引起电容器组谐振和谐波电流放大，导致电缆线路过负荷；3、使变压器，电动机等设备产生附加损耗，引起发热现象，导致绝缘损坏；4、使感应式测量仪表产生计量误差。如何减少谐波的影响呢？1、减少非线性负载的使用，如：变频器和电子设备，降低谐波源的产生；2、提升电压等级和扩大设备容量，提高电网对谐波的抗性；3、使用谐波抑制装置来减少谐波，提高电能质量以及设备运行的稳定性。What are even harmonics and how to control it?Think of electricity as water, just as water can contain impurities, Electricity can also contain  impurities, these impurities in electricity are called harmonics.Any electrical frequency that is not 50Hz, is called a harmonic, Among these, harmonics with frequencies that are even multiples of the fundamental frequency are referred to as "even-order harmonics".What are the potential hazards of harmonics?1、Interference with signals of relay protection and automatic devices, causing maloperation;2、Triggering resonance and harmonic current amplification in capacitor banks, leading to overload conditions in cable circuits;3、Generating additional losses in equipment such as transformers and motors, causing heating effects that lead to insulation damage;4、Causing metering errors in induction-type measuring instruments.How to reduce the impact of harmonics?1、Reduce the use of non-linear loads (e.g., variable frequency drives and electronic equipment), to minimize harmonic generation at the source;2、Raise voltage levels and expand equipment capacity to enhance the power grid's immunity to harmonics;3、Utilize harmonic suppression devices to reduce harmonics, improve power quality, and enhance operational stability of equipment.

发布：2025-09-28      浏览：504

功率因素是什么？

功率因数PF等于有功功率（千瓦）除以视在功率（千伏安），公式为：‌PF = 有功功率（kW） ÷ 视在功率（kVA）。打个比方，我们购买一杯啤酒，以杯子大小来支付费用。但是在杯子中有啤酒和啤酒沫，啤酒越多泡沫就越少，我们的花费就更划算。啤酒代表有功功率，是我们真正需要的有用的商品；泡沫代表无功功率，是没用的商品，我们不能使用它，所以不想要太多。它们合在一起就是视在功率，是我们的实际功率。所以说功率因数就是有用功率与实际功率的比值，或者说是啤酒和我们所支付杯子大小的比值。您理解了吗？What is power factor?Power factor (PF) is equal to the active power (kW) divided by the apparent power (kVA), expressed by the formula:PF = Active Power (kW) ÷ Apparent Power (kVA).For example, when we buy a beer, we pay the cost based on the size of the glass.However, in the glass, there is both beer and foam. The more beer there is, the less foam there will be, making our spending more cost-effective.The beer represents active power, which is the useful commodity we truly need; the foam represents reactive power, which is a useless commodity that we cannot utilize and therefore do not want too much of.They together form the apparent power, which is the total power we actually handle. Therefore, the power factor is the ratio of useful power to the apparent power, or in other words, the ratio of beer to the size of the glass we pay for. Does this make sense?

发布：2025-09-26      浏览：344

如何理解50Hz交流电？

50Hz是我们中国交流电的频率，其含义是：一秒钟之内，交流电按照正弦波变化了50次，T1~T3是一个完整的周期，时长为：1秒除以50等于0.02秒，T1~T2，T2~T3都是0.01秒，这表示一个周期内电流有两次瞬间为零，但灯泡为什么没有出现闪烁呢？主要原因有两个：其一，闪烁速度太快，人眼难以察觉；其二，灯泡靠加热灯丝发光，电流瞬间过零时灯丝无法完全冷却，光会减弱但看上去依然是连贯的。How to understand 50Hz alternating current?50Hz is the frequency of alternating current in China, and its meaning is: within one second, the alternating current changes 50 times according to the sine wave. T1 to T3 constitutes one complete cycle with a duration of 1 second divided by 50, equaling 0.02 seconds. Both T1 to T2 and T2 to T3 are 0.01 seconds. This means that the current is instantaneously zero twice in one cycle, but why doesn't the light bulb flicker? There are two main reasons:first, the flickering speed is too fast for the human eye to detect; second, the light bulb emits light by heating the filament, and when the current is instantaneously zero, the filament cannot cool down completely, so the light will dim but still appear continuous.

发布：2025-09-23      浏览：1428

谐波治理：从源头抑制到末端消除

要理解 “谐波” 及 “谐波治理”，需要先从电能的基础形态切入，再逐步拆解其产生、危害与解决思路。以下是系统且通俗的讲解：一、什么是谐波？—— 从 “标准电” 到 “畸形电” 的偏差我们日常使用的电能（如家庭 220V、工业 380V），本质是正弦交流电—— 它的电压 / 电流波形是光滑的 “正弦曲线”（像平稳起伏的波浪），频率固定（我国为 50Hz，称为 “基波”，是电能传输和设备正常工作的 “标准形态”）。而谐波，就是叠加在 “基波” 上的 “额外波形”：当电路中存在 “非线性负载”（即电流与电压不是正比关系的设备）时，会打乱原本光滑的正弦波，产生频率是基波整数倍的 “畸形波”—— 比如 100Hz（2 倍基波，2 次谐波）、150Hz（3 次谐波）、250Hz（5 次谐波）等，这些 “额外的波” 就是谐波。1. 谐波的核心特点频率特性：谐波频率 = 基波频率 × 整数 n（n=2,3,4...，n 越大，谐波 “频率越高、幅值越小”，通常关注 n≤25 的低次谐波）；寄生性：谐波本身不传递有用功率，是 “电能污染”，会消耗额外电能、干扰设备；来源集中：90% 以上的谐波来自 “非线性负载”，常见场景如下： 2. 谐波的危害 —— 为何必须治理？谐波不是 “无害的波动”，它会从电网、设备、安全三个维度造成问题：对电网：增加输电线路损耗（谐波电流会额外发热）、导致变压器过载 / 噪音变大、影响电能计量（电表可能多走字）；对设备：干扰精密仪器（如 PLC、传感器）误动作、缩短电机 / 电容寿命（谐波电流会让设备 “无效做功” 并过热）、引发电压不稳（导致灯光闪烁、电脑蓝屏）；极端风险：严重时可能引发电网谐振，烧毁变压器或开关设备，甚至造成局部停电。二、如何治理谐波？—— 从 “源头抑制” 到 “末端消除”谐波治理的核心思路是：要么减少谐波的产生（源头控制），要么抵消已产生的谐波（末端治理），具体可分为三大类方案：1. 源头抑制：从 “产生端” 减少谐波（最根本的方式）通过选择低谐波特性的设备，直接降低谐波的 “输出量”，避免问题扩散。常见手段：选用 “低谐波负载”：比如购买带 “低谐波认证” 的变频器（如符合 GB/T 14549 标准）、LED 灯（选择带主动功率因数校正的驱动）；优化设备参数：比如对电焊机、电弧炉等设备，增加 “电抗器” 或 “缓冲电路”，让电流波形更接近正弦波；合理规划负载布局：避免大量非线性设备集中在同一回路（比如充电桩群、数据中心服务器，可分散到不同配电支路，减少谐波叠加）。2. 末端治理：用 “补偿设备” 抵消已产生的谐波（最常用的方式）当源头无法完全控制时，在谐波集中的 “配电节点”（如车间配电箱、楼宇配电室）安装专用设备，主动抵消谐波，恢复电网波形。主流设备有 3 种，适用场景差异较大： 3. 系统优化：通过 “电网结构” 降低谐波影响（辅助手段）当谐波问题涉及整个厂区或园区时，通过调整电网的 “传输路径” 或 “阻抗特性”，减少谐波的传播和放大：增加 “隔离变压器”：在非线性设备与主电网之间加装隔离变压器（如干式变压器），阻断谐波向主电网扩散；提高电网短路容量：通过增大配电线路截面积、缩短供电距离，降低电网阻抗，减少谐波导致的电压畸变（简单说：让电网 “更强壮”，抗谐波干扰能力更强）；安装 “电能质量监测仪”：实时监测电网谐波含量（如符合 IEC 61000-4-30 标准的监测仪），定位谐波源头，为治理方案提供数据支撑（避免盲目安装补偿设备）。三、谐波治理的关键原则实际应用中，并非 “设备越贵越好”，而是要遵循 “先诊断、再选型” 的逻辑：1. 先检测：用电能质量监测仪测 3-7 天，明确谐波的 “主要次数、最大幅值、波动规律”（比如是 3 次谐波为主，还是 5 次 + 7 次混合）；2. 分场景：负载稳定选 “无源滤波器”，负载波动大选 “APF”，高功率复杂场景选 “混合滤波器”；3. 控成本：优先从源头优化（比如换低谐波设备），再考虑末端治理（避免盲目上 APF 造成浪费）。总体来说，谐波治理的本质是 “让畸形的电网波形，重新变回平稳的正弦波”，最终实现 “节能、保设备、稳电网” 的目标。

发布：2025-08-28      浏览：606