Selection criteria for aluminum electrolytic capacitors

Key points of type selection

Rated voltage

The capacitance and pressure tolerance on the aluminum electrolytic capacitor body are two important parameters, which are the most basic content for capacitor selection. In the actual selection of capacitors, capacitors with larger capacity are used in places where the current changes quickly, rather than where larger capacity is required. First, the cost and quantity may increase as capacity increases. In addition, the greater the capacity, the greater the charging current and the longer the charging time. These are all considerations in practical application selection.

Rated operating voltage: The maximum DC voltage that the capacitor can withstand for a long time within the specified operating temperature range. In AC circuits, it must be noted that the maximum AC voltage cannot exceed the DC voltage of the capacitor. The commonly used fixed capacitor working voltage is 6.3V, 10V16V25V50V63V100V400V450v575V 500V600V. The actual voltage that the capacitor must withstand in the loop cannot exceed its withstand voltage.

In the filter circuit, the capacitor voltage tolerance value should not be less than 1.42 times the AC effective value. Another issue to consider is the operating voltage margin, which is usually higher than 15%.

The rated voltage of the capacitor has a large margin, which can reduce the internal resistance, leakage current, loss angle and life. Although the 48v working voltage uses a 50v aluminum electrolytic capacitor in a short time, its life is likely to decrease over time.

Moderate wear and tear

The energy consumed by the capacitor in the electric field is usually expressed as the ratio of the dissipated power to the reactive power of the capacitor, that is, the tangent value of the loss angle. The larger the loss angle, the larger the capacitor loss, and the larger the fault tolerance angle is, the capacitor is not suitable for high-frequency operation. There is a dissipation factor in all capacitors, and sometimes the DF value is expressed as the loss angle of TANδ. The lower the parameter, the better. Aluminum electrolytic capacitors are a higher parameter.

The DF value is related to the temperature, capacitance, voltage and frequency of the same brand and series of capacitors. When the capacity is the same, the higher the pressure tolerance, the lower the DF value. In addition, the higher the temperature, the higher the DF value, the higher the frequency.

Outside size

The appearance size is related to the weight and shape of the pin. The single end is a radial wire, the screen is a locking screw, there are patches, aluminum electrolytic capacitors, etc. As for the weight, the capacitance and pressure tolerance are the same, but the weight of the two brands of capacitors must be different; the shape and size are more related to the planning of the housing. In general, capacitors of the same diameter and capacity can be replaced with low capacitance, but the interference mechanism is considered when replacing low capacitance with long capacitance.