ENGINEERING TECHNICAL PAPERS


  RF Capacitor Performance Data for Multilayer
Types MC & MCH Chips and Clad SMT Types Min & MCM
ESR vs. Frequency, RMS Current vs. Frequency, Q vs. Frequency, Impedance vs. Frequency


  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 routinelyused as input bus capacitors in the power supplysections of electronic equipment such as motordrives, UPS systems, and welders. Most of thesecapacitors 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.


  Performance of MLP and MLS Flatpack Aluminum Capacitors
Cornell Dubilier offers 85°C Type MLP flatpack aluminum cased electrolytic capacitors and 125°C Type MLS flatpack stainless cased electrolytic capacitors for higher temperature and current. This paper explains the 25-year shelf life capability, the 50 and 100-year expected lifetimes, use of MLP and MLS in military systems, heatsinking MLP and MLS capacitors and high-voltage applications of MLP's.


  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.


  Solid Polymer Aluminum Capacitor Chips in DC-DC Converter Modules
The 125°C, solid polymer aluminum (SPA) capacitors have performance advantages over other types of low ESR capacitors when used as output filters in DC-DC modules. The principal advantage of an SPA capacitor is that its ultra low ESR permits filtering in a DC-DC converter with fewer capacitors. This reduces the cost and size of the converter. This paper shows the performance advantages of the new Type ESRH, 125°C, SPA capacitor in DC-DC modules.


  Design of Snubbers for Power Circuits
Snubbers are suppression circuits which are placed across IGBTs and switching transistors in power conversion circuits to suppress voltage transients and protect semiconductor devices from overvoltage. This paper shows how to design resistor-capacitor (RC) damping snubbers and the resistor-capacitor-diode (RCD) turn-off snubbers.


  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.


  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.