三和SAMWHA鋁電解電容器選型要點：容量、耐壓、溫度范圍、元件封裝形式與尺寸、紋波電流、漏電流、ESR、散逸因數、阻抗/頻率特性、電容壽命、實際需要、性能和成本等。

　　Key points of aluminum electrolytic capacitor selection: capacity, withstand voltage, temperature range, component packaging form and size, ripple current, leakage current, ESR, dissipation factor, impedance / frequency characteristics, capacitor life, actual needs, performance and cost, etc.

　　鋁電解電容是以經過蝕刻的高純度鋁箔作為陽極，以浸有電解液的薄紙或布做陰極構成的極性電容器。優點：容量大、耐壓高、價格便宜；缺點：漏電流大、誤差大、穩定性差、壽命隨溫度的升高下降很快。

　　Aluminum electrolytic capacitor is a polar capacitor composed of etched high-purity aluminum foil as anode and thin paper or cloth soaked with electrolyte as cathode. Advantages: large capacity, high pressure resistance and low price; Disadvantages: large leakage current, large error, poor stability, and the service life decreases rapidly with the increase of temperature.

　　1、容量和額定工作電壓

　　Capacity and rated operating voltage

　　鋁電解電容本體上標有的容量和耐壓，這兩個參數是很重要，是選用電容最基本的內容。在實際電容選型中，對電流變化節奏快的地方要用容量較大的電容，但并非容量越大越好，首先，容量增大，成本和體積可能會上升，另外，電容越大充電電流就越大，充電時間也會越長。這些都是實際應用選型中要考慮的。

　　The capacity and withstand voltage marked on the body of aluminum electrolytic capacitor are very important and the most basic content of capacitor selection. In the actual capacitor selection, the capacitor with larger capacity should be used where the current change rhythm is fast, but the larger the capacity is, the better. Firstly, the larger the capacity is, the cost and volume may rise. In addition, the larger the capacitance is, the greater the charging current is and the longer the charging time will be. These are to be considered in practical application selection.

　　（在電路設計中，電容的容量大小直接關系到電路的穩定性，例如：根據公式“C＝I/(△V/△t)”，假設某電路平均電流為 6A，△V=50mV，△t=10μS，就可計算出此處對電容總容量的要求為1200μF。如果選用1000UF 可能在短期內不會出現問題，但長時間運行就會出現電容暴漿等故障。在電路設計過程中，并不是電容越大，濾波效果越好，這要看具體電路，在低頻電路中，電容值越大，對紋波的濾除效果就越好，但如果有高頻信號，就不一定了。在高頻段要選擇合適的電容值和電容類型，一般采用云母電容和高頻瓷片電容，電容值一般都比較小。）

　　(in circuit design, the capacity of the capacitor is directly related to the stability of the circuit. For example, according to the formula "C = I / (△ V / △ T)", suppose that the average current of a circuit is 6a, △ v = 50mV, △ t = 10 μ S. It can be calculated that the requirement for the total capacitance here is 1200 μ F。 If 1000uf is selected, there may be no problem in the short term, but faults such as capacitor slurry explosion will occur in long-term operation. In the process of circuit design, it is not that the larger the capacitance, the better the filtering effect, which depends on the specific circuit. In the low-frequency circuit, the larger the capacitance, the better the ripple filtering effect, but if there is a high-frequency signal, it is not necessarily. Appropriate capacitance value and type shall be selected in the high-frequency band. Mica capacitance and high-frequency ceramic chip capacitance are generally used, and the capacitance value is generally small.)

　　額定工作電壓：在規定的工作溫度范圍內，電容長期可靠地工作，它能承受的最大直流電壓。在交流電路中，要注意所加的交流電壓最大值不能超過電容的直流工作電壓值。電容在電路中實際要承受的電壓不能超過它的耐壓值。在濾波電路中，電容的耐壓值不要小于交流有效值的1.42倍。另外還要注意的一個問題是工作電壓裕量的問題，一般來說要在15％以上。例如某電容的額定電壓是50V，雖然涌浪電壓可能高至63V，但一般最高只會施加42V電壓。讓電容器的額定電壓具有較多的裕量，能降低內阻、降低漏電流、降低損失角、增加壽命。

　　Rated working voltage: the maximum DC voltage that the capacitor can withstand when it works reliably for a long time within the specified working temperature range. In the AC circuit, it shall be noted that the maximum AC voltage applied shall not exceed the DC working voltage of the capacitor. The actual voltage to be borne by the capacitor in the circuit shall not exceed its withstand voltage value. In the filter circuit, the withstand voltage value of the capacitor shall not be less than 1.42 times of the AC effective value. Another problem to pay attention to is the working voltage margin, which is generally more than 15%. For example, the rated voltage of a capacitor is 50V. Although the surge voltage may be as high as 63v, generally only 42V will be applied at most. The rated voltage of the capacitor has more margin, which can reduce the internal resistance, reduce the leakage current, reduce the loss angle and increase the service life.

　   2、介質損耗

　　Dielectric loss

　　電容器在電場作用下消耗的能量，通常用損耗功率和電容器的無功功率之比，即損耗角的正切值表示，損耗角大的電容不適于高頻情況下工作。

　　The energy consumed by the capacitor under the action of electric field is usually expressed by the ratio of loss power to reactive power of the capacitor, that is, the tangent of loss angle. The capacitor with large loss angle is not suitable for working at high frequency.

　　3、外型尺寸

　　Overall dimension

　　外型尺寸與重量及接腳型態相關。single ended是徑向引線式，screw是鎖螺絲式，另外還有貼片鋁電解電容等。至于重量，同容量同耐壓，但品牌不同的兩個電容做比較，重量一定不同；而外型尺寸更與外殼規劃有關。一般來說，直徑相同、容量相同的電容，高度低的可以代用高度大的電容，但是長度高的替代低的電容時就要考慮結構干涉問題。

　　The external dimension is related to the weight and pin type. Single ended is radial lead type, screen is lock screw type, in addition, there are SMD aluminum electrolytic capacitors, etc. As for the weight, if you compare two capacitors with the same capacity and withstand voltage but different brands, the weight must be different; The external dimension is more related to the shell planning. Generally speaking, for capacitors with the same diameter and capacity, those with low height can replace those with high height, but when replacing low capacitance with those with high length, the problem of structural interference should be considered.

　　4、ESR

　　一個等效串聯電阻很小的電容相對較大容量的外部電容能很好地吸收快速轉換時的峰值（紋波）電流。用ESR大的電容并聯更具成本效益。然而,這需要在PCB面積、器件數目與成本之間尋求折衷。

　　A capacitor with a small equivalent series resistance can absorb the peak (ripple) current during fast conversion compared with an external capacitor with a large capacity. Parallel connection with capacitors with large ESR is more cost-effective. However, this requires a compromise between PCB area, number of devices and cost.

　　5、紋波電流和紋波電壓

　　Ripple current and ripple voltage

　　其實就是 ripple current，ripple voltage，含義就是電容器所能耐受紋波電流/電壓值。紋波電壓等于紋波電流與ESR的乘積。當紋波電流增大的時候，即使在ESR保持不變的情況下，紋波電壓也會成倍提高。換言之，當紋波電壓增大時，紋波電流也隨之增大，這也是要求電容具備更低 ESR值的原因。疊加入紋波電流后，由于電容內部的等效串連電阻引起發熱，從而影響到電容器的使用壽命。一般的，紋波電流與頻率成正比，因此低頻時紋波電流也比較低。額定紋波電流是在最高工作溫度條件下定義的數值。而實際應用中電容的紋波承受度還跟其使用環境溫度及電容自身溫度等級有關。規格書通常會提供一個在特定溫度條件下各溫度等級電容所能夠承受的最大紋波電流。甚至提供一個詳細圖表以幫助使用者迅速查找到在一定環境溫度條件下要達到某期望使用壽命所允許的電容紋波量。

　　In fact, it means ripple current and ripple voltage that the capacitor can withstand. The ripple voltage is equal to the product of ripple current and ESR. When the ripple current increases, the ripple voltage will increase exponentially even when the ESR remains unchanged. In other words, when the ripple voltage increases, the ripple current also increases, which is why the capacitor is required to have a lower ESR value. After adding ripple current, the equivalent series resistance inside the capacitor will cause heating, which will affect the service life of the capacitor. Generally, the ripple current is directly proportional to the frequency, so the ripple current is also relatively low at low frequency. The rated ripple current is defined at the maximum operating temperature. In practical application, the ripple tolerance of the capacitor is also related to the ambient temperature and the temperature level of the capacitor itself. The specification usually provides the maximum ripple current that each temperature grade capacitor can withstand under specific temperature conditions. A detailed chart is even provided to help users quickly find out the allowable capacitance ripple to achieve a certain expected service life under certain ambient temperature conditions.

　　6、漏電流Leakage current

　　電容器的介質對直流電流具有很大的阻礙作用。然而，由于鋁氧化膜介質上浸有電解液，在施加電壓時，重新形成的以及修復氧化膜的時候會產生一種很小的稱之為漏電流的電流。通常，漏電流會隨著溫度和電壓的升高而增大。一般來說，電容器容量愈高，漏電流就愈大。從公式可得知額定電壓愈高，漏電流也愈大，因此降低工作電壓亦可降低漏電流。

　　The dielectric of the capacitor has a great hindrance to the DC current. However, because the aluminum oxide film medium is immersed in electrolyte, a small current called leakage current will be generated when the voltage is applied, and when the oxide film is re formed and repaired. Usually, the leakage current increases with the increase of temperature and voltage. Generally speaking, the higher the capacitor capacity, the greater the leakage current. It can be seen from the formula that the higher the rated voltage is, the greater the leakage current is. Therefore, reducing the working voltage can also reduce the leakage current.

　　7、壽命life

　　影響電容壽命的原因有很多，過電壓，逆電壓，高溫，急速充放電等等，正常使用的情況下，最大的影響就是溫度，因為溫度越高電解液的揮發損耗越快。需要注意的是這里的溫度不是指環境或表面溫度，是指鋁箔工作溫度。

　　There are many reasons affecting the service life of capacitors, such as overvoltage, reverse voltage, high temperature, rapid charge and discharge, etc. under normal use, the biggest impact is temperature, because the higher the temperature, the faster the volatilization loss of electrolyte. It should be noted that the temperature here does not refer to the ambient or surface temperature, but refers to the working temperature of aluminum foil.