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Rated voltage Dielectric loss

Date: 2021-12-31
Rated voltage
The capacity and withstand voltage marked on the aluminum electrolytic capacitor body, these two parameters are very important, and they are the most basic content for the selection of capacitors. In the actual capacitor selection, a larger capacity capacitor should be used where the current changes quickly, but it is not that the larger the capacity is, the better. First of all, the larger the capacity, the cost and volume may increase. In addition, the larger the capacitor, the higher the charging current. The larger the charging time, the longer. These are all considerations in the actual application selection.
Rated operating voltage: The maximum DC voltage that the capacitor can withstand for a long time and reliably within the specified operating temperature range. In an AC circuit, it is important to note that the maximum AC voltage applied cannot exceed the DC working voltage value of the capacitor. Commonly used fixed capacitor operating voltages are 6.3V, 10V, 16V, 25V, 50V, 63V, 100V, 200V, 250V, 400V, 450V, 475V, 500V, 600V, 630V. The voltage that the capacitor actually has to withstand in the circuit cannot exceed its withstand voltage.
In the filter circuit, the withstand voltage value of the capacitor should not be less than 1.42 times the effective value of the AC. Another issue to note is the working voltage margin, which is generally above 15%.
Let the rated voltage of the capacitor have more margin, which can reduce the internal resistance, reduce the leakage current, reduce the loss angle, and increase the life. Although the 48V working voltage uses 50V aluminum electrolytic capacitors for a short time, there will be no problems, but after long use, the lifespan may be reduced.
Dielectric loss
The energy consumed by a capacitor under the action of an electric field is usually expressed by the ratio of the loss power to the reactive power of the capacitor, that is, the tangent value of the loss angle (in the equivalent circuit of the capacitor, the series equivalent resistance ESR is equal to the capacitive reactance 1/ωC It is called Tan δ, where the ESR is calculated at 120Hz. Obviously, Tan δ increases with the increase of the measurement frequency and increases with the decrease of the measurement temperature). The greater the loss angle, the greater the loss of the capacitor, and the capacitor with a large loss angle is not suitable for high-frequency operation. Dissipation factor (DF) exists in all capacitors, and sometimes the DF value is expressed by the loss angle tanδ. The lower the parameter, the better. However, this parameter is relatively high for aluminum electrolytic capacitors.
Whether the DF value is high or low is related to the temperature, capacity, voltage, frequency, etc. for capacitors of the same brand and series; when the capacity is the same, the higher the withstand voltage, the lower the DF value. In addition, the higher the temperature, the higher the DF value, and the higher the frequency, the higher the DF value.
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