Category | Selection of Components

V-I Characteristics - Varistors

Posted on 04 May 2020

              Varistor V-I characteristic forms of representation When selecting metal oxide varistors for specific applications, it is often convenient to use a mathematical representation of the V-I characteristics of the varistors being considered. Generally, a suitable approximation to the V-I behavior of a varistor can be accomplished by use [...]

Improve Current Carrying Capacity by Proper Heat Sink Selection

Posted on 26 April 2020

              Heat sinks and cooling profiles are an excellent means of removing heat from higher power components. For higher power semiconductor components (e.g. more than 15 A), cooling plates are no longer sufficient to fully utilise the current carrying capacity. Instead, solid heat sinks or cooling profiles made of [...]

Criteria for Successful Selection of Diodes and Thyristors

Posted on 23 April 2020

              Thyristor and Rectifier Dimensioning and Selection The general guidelines given in the article "Criteria for Successful Selection of IGBT and MOSFET Modules" are to be applied by analogy to the selection of thyristors, rectifier diodes and thyristor/diode modules. For operation at a line frequency of 50/60 Hz, any additional [...]

Calculating the Useful Life of Capacitors

Posted on 23 April 2020

  Useful life (also termed service life or operational life) is defined as the life achieved by the capacitor without exceeding a specified failure rate. Total failure or failure due parametric variation is considered to constitute the end of the useful life. Depending on the circuit design, device failure due to parametric variation does not [...]

PSpice Simulation Model

Posted on 19 April 2020

  Varistor model The development of a varistor model for the “PSpice Design Center” circuit simulation program allows varistors to be integrated into computer assisted development of modern electronic circuitry. In the PSpice modeling concept, a varistor is represented by its V/I characteristic curve, a parallel capacitance, and a series inductance. The structure of this [...]

Criteria for Successful Selection of IGBT and MOSFET Modules

Posted on 15 April 2020

  Below are several important criteria that should be considered when selecting IGBT and MOSFET modules. 1.) Operating voltage Blocking voltage Since most power modules are used in DC voltage links which are AC-voltage supplied via single-phase or three-phase rectifier bridges, the blocking voltages of IGBT and MOSFET modules are adjusted to common line voltage [...]

Dimensioning Semiconductor Fuses

Posted on 15 April 2020

  The following fuse-related data must be considered when dimensioning semiconductor fuses: Rated current Rated voltage Operating i²t value Switching voltage Dimensioning semiconductor fuses on the basis of the rated current At rated current, a fuse link can be continually loaded under certain circumstances, i.e. at 20°C ambient temperature in unobstructed air. The current has to be [...]

Selection Guide - Varistors

Posted on 07 April 2020

    Choosing a varistor involves three main steps: Select varistors that are suitable for the operating voltage. Determine the varistor that is most suitable for the intended application in terms of: a) surge current b) energy absorption c) average power dissipation (for a and b also estimating the number of repetitions) Determine the maximum [...]

Film Capacitors for DC-Link

Posted on 07 April 2020

              DC-Link or DC intermediate circuits are energy storage devices that connect several electricity grids by inverters on a joint current and voltage level. Requirements for film capacitors for DC-Links are: - High CV (capacitance x voltage) product - Compact - Over-voltage (DC) capability - Low losses (ESR) with high current [...]

Reverse Voltage

Posted on 05 April 2020

              When selecting power components for specific applications, certain factors have to be considered. These factors include the components’ voltage and current ratings under the possible cooling conditions, as well as the permissible operating ranges. These factors have to be looked at in every possible stationary and short-time operating [...]