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Choose the right oneLong life Electrolytic capacitorThe voltage, capacity, and other parameters of the Electrolytic capacitor should be selected according to the use scenario. What does the different parameters of the long-life Electrolytic capacitor mean?
(1) Rated voltage VR: It is designed when designing a capacitor and represents the DC voltage on the capacitor. For aluminum Electrolytic capacitor, the rated voltage ≤ 100 V is usually called low-voltage capacitance, while the rated voltage>100 V is called (medium) high-voltage capacitance. The commonly used rated voltages are 6.3V, 10V, 16V, 25V, 50V, 63V, 100V, 250V, 400V, 450V, 500V, 630V, etc.
(2) Working voltage VOP: The capacitor can continuously operate within the rated working range at the rated voltage (including some superimposed components). The allowable continuous working voltage range is between 0V and rated voltage. In a short period of time, due to the presence of an air oxide layer on the cathode aluminum foil, the capacitor can withstand a reverse voltage of no more than 1.5 V.
(3) Surge voltage VS: refers to the maximum voltage that can be applied to a capacitor in a short period of time, such as 5 times within an hour, each time for one minute. IEC 60384-4 defines surge voltage as follows: if VR ≤ 315 V, VS=1.15VR; if VR>315 V, VS=1.10VR.
(4) Nameplate capacity CR: is the AC capacitance value designed and marked by the capacitance. CR is measured according to the special standards specified in (IEC 60384-1 and IEC 60384-4). For Electrolytic capacitor, the general test conditions are twice the power frequency (100HZ or 120HZ) and room temperature. In addition, the capacity error is that the actual capacity of the capacitance leaves the distribution range of Nameplate capacity, which is generally marked on the body. For AL electrolysis, it is basically marked as M (± 20%).
(5) Usage temperature range: refers to the temperature range within which capacitors can operate stably. Currently, the common low temperature limit values are generally -55 ℃, -40 ℃, -25 ℃, and the high temperature limit values are generally 85 ℃, 105 ℃, 125 ℃, 130 ℃, etc.
(6) Service life: service life (also defined as service life and operating life) is defined as the achievable life of the capacitor that does not exceed the specified Failure rate. The service life is obtained by applying experience and accelerated aging tests. If the load is below the rated value, the service life can be extended (such as low working voltage, current, and environmental temperature), and appropriate heat dissipation measures can also extend the service life.
(7) Dissipation factor tan δ： It is the ratio of Equivalent series resistance to the capacitive reactance component in the equivalent series line, or the ratio of active power (dissipated power) to reactive power under sinusoidal voltage.
(8) Equivalent series inductance ESL: the self inductance or Equivalent series inductance is derived from the internal design of terminal blocks and capacitors.
(9) Equivalent series resistance ESR: refers to the resistive component of the equivalent series circuit. The ESR value is related to frequency, temperature, and dissipation factor.
(10) Impedance Z: refers to the total reactance value of the equivalent series line, which only includes the capacitive reactance part of the capacity CS; Dielectric loss and Ohmic impedance ESR of electrolyte and terminal blocks; The inductive reactance ESL generated by capacitor winding and wiring terminals. ESL only depends on frequency, while capacitive reactance and resistive reactance depend on frequency and temperature.
(11) Leakage current Ileak: due to the special characteristics of aluminum Electrolytic capacitor, its aluminum oxide layer also acts as an insulation layer. After the DC voltage is applied for a long time, a small current will continue to flow through the capacitor. This current is called leakage current. A small leakage current means that the insulation layer of the capacitor is well designed.
(12) Ripple current: The RMS value is used to indicate the AC current flowing through the device, which is caused by jumping and surge voltage. The maximum allowable ripple current is determined by environmental temperature, capacitance surface area (heat dissipation area), dissipation factor, and AC frequency. Due to the decisive effect of thermal stress on the lifespan of capacitors, the heat generated by ripple currents is an important factor affecting their service life.