串聯諧振的原理是什么？

在 RLC 串聯交流電路中，流經電感元件與電容元件的電流為同一電流。由于電感電壓超前電流90°，電容電壓滯后電流90°，所以每時每刻，電感電壓總與電容電壓相反。當兩電壓幅值相等（感抗等于容抗）時，其電壓疊加值為零，即電感與電容構成的整體可等效視為短路。此時依據歐姆定律，電路電流可直接表示為電壓與電阻的比值，且電壓與電流相位一致。需注意，電感與電容兩端各自存在端電壓，其數值可能遠高于輸入電壓，此現象即被定義為串聯諧振過電壓。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.

發布：2025-11-03      瀏覽：40

電流互感器二次為什么不能開路？

正常運行時，二次電流產生的反向磁通抵消一次電流產生的磁通，使得鐵芯中總磁通較小，所以二次電壓接近為零。若二次斷開，二次電流為零，沒有反向磁通的抵消，一次電流產生的磁通就是總磁通，急劇變大，二次側將會出現高達數千伏的電壓，此時危險來臨。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.

發布：2025-10-27      瀏覽：74

有功功率、無功功率的關系

正常情況下，視在功率是指，容量固定不變，把視在功率看作圓的半徑，橫軸上投影是有功功率，縱軸上投影是無功功率，夾角就是功率因數角。當夾角為0時，功率因數為1，容量直接等于有功功率，那么當夾角為90°時，是什么情況呢？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°?

發布：2025-10-27      瀏覽：62

電容并聯或串聯后的三種狀態

相同參數的兩個電容并聯后，電容的耐壓值不變，但是容量翻兩倍！相同參數的兩個電容串聯后，耐壓值增加了兩倍，但是容量會減半！相同參數的兩個有極性電容背靠背反向串聯后就組成了無極性電容，電容的耐壓值不變，容量值減半！ 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!

發布：2025-10-21      瀏覽：90

三次諧波引發零線發熱怎么辦？

酒店、商超的零線發熱問題主要由三次諧波引起，有如下七種治理方案：一、在諧波源附近加裝LC無源濾波器、APF有源濾波器；二、更換優質開關電源，降低諧波，提升功率因數；三、調節三相負載，盡可能讓每一相負載均勻分布；四、加粗零線，提高零線的過流能力；五、匹配開關電源和負載的功率，避免“大馬拉小車”現象；六、在相線上串聯電抗器，并定期檢查中性線是否松動；七、推薦TN-S接地系統，錯峰運行高諧波設備。 ?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.  ?

發布：2025-10-20      瀏覽：88

10kV高壓電容柜要加電抗器嗎？

高壓電容補償柜通常由：高壓電容器、高壓電抗器和高壓智能控制器組成。投切電容器時合閘涌流是工作電流的幾十倍，降低了電容器的使用壽命，影響了供電質量。而電抗器具有抑制電流突變的能力，與電容器搭配能很好的抑制合閘涌流。另外電容器對諧波有放大作用，設備中的諧波會影響電容器的安全。串聯電抗器后可抑制特定次的諧波，12%、13%、14%能抑制3次及3次以上諧波及合閘涌流；5%、6%、7%能抑制5次及5次以上諧波及合閘涌流，電抗率越高抑制效果越好；1%只能抑制合閘涌流，不能抑制9次以下的諧波。因此，高壓電容柜加電抗器主要有兩個作用：一、限制電容器投切時的合閘涌流；二、抑制高次諧波。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.

發布：2025-10-09      瀏覽：177

SIC碳化硅有源濾波器有何優勢？

有源電力濾波器作為諧波治理的關鍵設備，需在高頻、高功率密度下實現快速動態響應。傳統硅基器件受限于開關損耗、導通電阻和溫度特性，難以滿足高效的需求。碳化硅（SIC）材料憑借其寬禁帶特性，以更低的導通損耗、更高的開關頻率和耐高溫能力，成為有源電力濾波器升級的顛覆性解決方案。主要具有以下優勢：1、SIC器件的開關頻率可達100kHz以上（甚至MHz級），而IGBT通常僅20kHz以下。高頻開關顯著提升諧波補償精度和動態響應速度，使有源電力濾波器能更精準捕捉并補償突變諧波。2、SIC導通壓降低至約1V，開關損耗比IGBT低50%以上。結合高頻特性，整機效率可突破99%，較傳統IGBT（97%）顯著提升。3、SIC材料可承受200℃以上高溫環境，而IGBT僅能穩定運行至125℃。高溫下SIC器件性能衰減較小，適合極端工況。4、SIC單管耐壓可達3300V+，而IGBT單管通常僅1200-1700V。高壓場景下，SIC無需多管串聯，簡化電路設計并降低故障概率。5、采用SIC的S機型體積減少超40%，重量降低超35%，顯著節省安裝空間。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.

發布：2025-09-29      瀏覽：219

什么是偶次諧波以及如何治理？

把電看作是水，水里面有雜質，電里面也會有雜質，電里面的雜質稱之為諧波。只要電的頻率不是50Hz，都叫做諧波，其中額定頻率為基波頻率偶數倍的諧波，稱為“偶次諧波”。諧波會造成哪些危害呢？1、對繼電保護和自動裝置的信號產生干擾造成誤動作；2、引起電容器組諧振和諧波電流放大，導致電纜線路過負荷；3、使變壓器，電動機等設備產生附加損耗，引起發熱現象，導致絕緣損壞；4、使感應式測量儀表產生計量誤差。如何減少諧波的影響呢？1、減少非線性負載的使用，如：變頻器和電子設備，降低諧波源的產生；2、提升電壓等級和擴大設備容量，提高電網對諧波的抗性；3、使用諧波抑制裝置來減少諧波，提高電能質量以及設備運行的穩定性。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.

發布：2025-09-28      瀏覽：240

功率因素是什么？

功率因數PF等于有功功率（千瓦）除以視在功率（千伏安），公式為：?PF = 有功功率（kW） ÷ 視在功率（kVA）。打個比方，我們購買一杯啤酒，以杯子大小來支付費用。但是在杯子中有啤酒和啤酒沫，啤酒越多泡沫就越少，我們的花費就更劃算。啤酒代表有功功率，是我們真正需要的有用的商品；泡沫代表無功功率，是沒用的商品，我們不能使用它，所以不想要太多。它們合在一起就是視在功率，是我們的實際功率。所以說功率因數就是有用功率與實際功率的比值，或者說是啤酒和我們所支付杯子大小的比值。您理解了嗎？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?

發布：2025-09-26      瀏覽：206

如何理解50Hz交流電？

50Hz是我們中國交流電的頻率，其含義是：一秒鐘之內，交流電按照正弦波變化了50次，T1~T3是一個完整的周期，時長為：1秒除以50等于0.02秒，T1~T2，T2~T3都是0.01秒，這表示一個周期內電流有兩次瞬間為零，但燈泡為什么沒有出現閃爍呢？主要原因有兩個：其一，閃爍速度太快，人眼難以察覺；其二，燈泡靠加熱燈絲發光，電流瞬間過零時燈絲無法完全冷卻，光會減弱但看上去依然是連貫的。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.

發布：2025-09-23      瀏覽：376