Aluminum electrolytic capacitor * selection guide
Capacity and rated voltage
Aluminum electrolytic capacitor marked on the body of the volume and pressure, these two parameters is very important, is the most basic content choose capacitance.
In actual capacitance type selection, fast to current change places with a large capacity of capacitance, but not the capacity is bigger, the better, first of all, increases capacity, cost and volume could increase, in addition, the greater the capacitance charging current, charging time will be longer.These are the actual application to consider in the selection.
Rated voltage: the specified working temperature range, capacitance work reliably for a long time, it can withstand the largest dc voltage.In ac circuits, attention should be paid to the ac voltage of the maximum value cannot exceed the dc working voltage value of the capacitance.Commonly used fixed capacitor voltage is 6.3 V, 10 V, 16 V, 25 V, 50 V, 63 V, 100 V, 250 V, 400 V, 500 V, 630 V.Capacitance in circuit actually bear the pressure value of voltage can't exceed it.
In the filter circuit, capacitance pressure values do not less than 1.42 times of ac RMS.Also, pay attention to a problem is the working voltage margin, generally in more than 15%.
Let the rated voltage of the capacitor with more margin, can reduce the internal resistance, to reduce the leakage current, reduce the loss Angle and increased longevity.Although say, 48 v working voltage using 50 v aluminum electrolytic capacitor short time there is no problem, but used for a long time, it may reduce service life.
Capacitor under the effect of electric field energy, usually in the ratio of the loss of power and capacitor reactive power, namely the loss Angle tangent value (in the equivalent circuit of capacitor, the equivalent series resistance ESR with capacitive reactance 1 / C ratio of omega is called Tan delta, where the ESR value is calculated under 120 hz. Obviously, Tan delta increased with the increase of frequency measurement, along with the decline of measuring temperature increase).Loss Angle, the greater the loss of capacitor, the greater the loss Angle large capacitor is not suitable for high frequency work.Dissipation factor dissipationfactor (DF) exists in all capacitor, sometimes DF values to loss Angle tan delta said.This parameter is very low.But the aluminum electrolytic capacitor this parameter is high.
DF value is high or low, in terms of the same brand, the same series capacitor, and temperature, capacity, voltage, frequency...Have a relationship;When the capacity is at the same time, the higher the pressure of DF value is low.In addition, the higher the temperature the higher the value of DF, the higher the frequency of DF value will be higher.
Installation dimensions related to weight and pin type.Single ended is radial lead type, screw lock screw type, and SMD aluminum electrolytic capacitors etc.As for the weight, and the capacity and the pressure, but different brands of two capacitors, weight must be different;And installation dimensions are more related to housing planning.In general, the diameter of the same capacity and capacitance, low height can substitute highly large capacitance, but the length of the high alternative low capacitance when consider agency interference problem.