串联谐振的原理是什么？

在 RLC 串联交流电路中，流经电感元件与电容元件的电流为同一电流。由于电感电压超前电流90°，电容电压滞后电流90°，所以每时每刻，电感电压总与电容电压相反。当两电压幅值相等（感抗等于容抗）时，其电压叠加值为零，即电感与电容构成的整体可等效视为短路。此时依据欧姆定律，电路电流可直接表示为电压与电阻的比值，且电压与电流相位一致。需注意，电感与电容两端各自存在端电压，其数值可能远高于输入电压，此现象即被定义为串联谐振过电压。What is the principle of series resonance?In an RLC series AC circuit, the current flowing through the inductive and capacitive elements is the same current. Due to the inductor voltage leading the current by 90 ° and the capacitor voltage lagging the current by 90 °, the inductor voltage is always opposite to the capacitor voltage at all times. When the amplitudes of two voltages are equal (inductance equals capacitance), the voltage superposition value is zero, which means that the whole composed of inductance and capacitance can be equivalently regarded as a short circuit. According to Ohm's Law, the current in a circuit can be directly expressed as the ratio of voltage to resistance, and the voltage and current phases are consistent. It should be noted that there is a terminal voltage at both ends of the inductor and capacitor, which may be much higher than the input voltage. This phenomenon is defined as series resonant overvoltage.

发布：2025-11-03      浏览：57

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：90

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：71

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：97

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：91

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：186

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：226

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：250

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：210

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：424