Aluminum Electrolytics Technical Papers

Inverter Output AC Filter Capacitor for Today's Demanding Applications

When specifying inverter output filter capacitors, the additional heating generated from the harmonic content of the system must be accounted for. If not, capacitor life will be shortened considerably. The filter capacitors selected should be designed to minimize losses in order to be able to dissipate the increased power generated by the harmonic currents. The increased peak voltage, caused by harmonic voltages superimposed on the fundamental waveform, should be examined as part of the design process. If the capacitor is not suitably sized, the dielectric can be damaged, causing premature failure.

Reliability of CDE Aluminum Electrolytic Capacitors

All design engineers who consider using aluminum electrolytic capacitors want to know how long they will last and how many they can expect to fail. Many engineers do not realize that these are actually two different but related questions. In this paper we define life and reliability in a manner that will hopefully make the distinction clear.

Deriving Life Multipliers for Electrolytic Capacitors

Aluminum electrolytic capacitors are routinely used as input bus capacitors in the power supply sections of electronic equipment such as motordrives, UPS systems, and welders. Most of these capacitors fail eventually from wearout. This article offers a brief explanation of how capacitor manufacturers quantify the effects of applied voltage, ripple current, frequency, ambient temperature, and airflow on capacitor life.

Improved Spice Models of Aluminum Electrolytic Capacitors for Inverter Applications

Impedance modeling of aluminum electrolytic capacitors presents a challenge to design engineers due to the complex nature of the capacitor construction. Unlike an electrostatic capacitor, an electrolytic capacitor behaves like a lossy coaxial distributed RC circuit element whose series and distributed resistances are strong functions of temperature and frequency. Existing public domain Spice models do not accurately account for this behavior. In this paper, a physics based approach is used to develop an improved impedance model that is interpreted both in pure Spice circuit models and in math functions.

Selecting & Applying Aluminum Electrolytic Capacitors for Inverter Applications

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 electrolytic bus capacitors for such power systems.

Heating in Aluminum Electrolytic Strobe & Photoflash Capacitors

Capacitor heating occurs in all aluminum electrolytic capacitor applications where a current is present, since the electrolytic capacitor is a nonideal capacitor which has resistive and other losses. Generally this heating is undesirable and is often a limit to the life of the capacitor. This paper explains the heating mechanisms so that life and reliability can be predicted.

Large-can aluminum electrolytic capacitors are widely used as bus capacitors in variable-speed drives, UPS systems and inverter power systems. Accurate thermal modeling of the capacitor's internal temperature is needed to predict life, and this is a challenge because of the anisotropic nature of the capacitor winding and the complexity of the thermal coupling between the winding and the capacitor case. This paper translates analytical models for heat flow in bus capacitors into an equivalent three-loop, seven-resistor, lumped-parameter thermal circuit model.

Predicting Life & Temperature of Aluminum Electrolytic Bus Capacitors with Thermal Modeling

Large-can aluminum electrolytic capacitors are widely used as bus capacitors in variable-speed drives, UPS systems and inverter power systems. Accurate thermal modeling of the capacitor's internal temperature is needed to predict life, and this is a challenge because of the anisotropic nature of the capacitor winding and the complexity of the thermal coupling between the winding and the capacitor case. This paper translates analytical models for heat flow in bus capacitors into an equivalent three-loop, seven-resistor, lumped-parameter thermal circuit model.

Thermal Modeling of Aluminum Electrolytic Capacitors

A comprehensive thermal model for screw-terminal aluminum electrolytic capacitors is developed in this paper. The test methodology and data upon which the model is based are discussed. Exact one-dimensional solutions, multi-dimensional heat equations, and finite-element analysis (FEA) model simulation results are presented. The effects of conduction, heat sinking, natural (free) convection, forced convection, and radiation are quantified and compared. Complex issues, such as anisotropism and multi-phase heat transfer, are discussed. A comparison of model results to test data is presented. Varying capacitor construction techniques are evaluated.