Photovoltaic inverter aluminum electrolytic capacitor

Abstract— Aluminum electrolytic capacitors are widely used in all types of inverter power systems, from variable-speed drives to welders to UPS units. This paper discusses the considerations involved in selecting the right type of aluminum electro-lytic bus capacitors for such power systems.

One of the main application classes of aluminum elec-trolytic capacitors is input capacitors for power invert-ers. The aluminum electrolytic capacitor provides a unique value in high energy storage and low device impedance. How you go about selecting the right ca-pacitor or capacitors, however, is not a trivial matter.

This paper will focus on three main capacitor types used in higher-power inverter applications: snapmount, plug-in, and screw-terminal capacitors. See Figure 2 below and Table 1 on page 3. Small snap-in's and radials are often used in the 100-1000 W range, and larger snapmount capacitors and snap-in farms are used in the 1-20 kW range.

And two 400V caps in parallel handily beat two 200V caps in series. Since the inverter market has grown and the bus volt-ages are greater than 150 volts, the market for high-voltage aluminum electrolytic capacitors has kept pace and reflected the shift in the power supply topology.

The effect of temperature on the degradation rate for aluminum electrolytic capacitors is based on the Arrhenius rate of chemical reaction of aluminum oxide (alumina). The activation energy Ea for a material is the average energy required to excite an electron of that material from its quantum potential well.

One might guess that since the highest-voltage capacitor market has grown immensely over the past 20 years at the expense of the low-voltage ca-pacitors, that high-voltage capacitors must offer some advantages to stringing lower-voltage capacitors in se-ries.