Snubber Capacitors for Complete Insurance of Power Semiconductors

The trend of modern semiconductor technology towards increasingly powerful applications results in the fact that switched currents and voltage levels are continuously increased and that simultaneously the switching speed is also increasing markedly.
The developments in the area of power semiconductors include the component group IGBT (Insulated Gate Bipolar Transistor) or IGBT modules.
The switching capacity with shortest switching times which can be realized using IGBTs necessitates an extremely low-inductance circuit design. Even the low self-inductance of the power bus may induce dangerous voltage overshoots between collector and emitter which may result in the destruction of the valuable power semiconductors.

Typical voltage
overshoot during
switch-off.

To protect the components, so-called snubber suppressor circuits are used. The most important component in this respect is a low-inductance pulse capacitor in order to attenuate or cut off peak voltages. In general, three basic snubber circuits are used with IGBTs.

Circuit A

Capacitor

Circuit B

Capacitor-resistor-diode

Circuit C

Capacitor-resistor-diode

In this context, the capacitor serves to suppress dangereous induced voltages which are produced during switching of the often very high currents. The most important criteria in selecting such capacitors are

- low self-inductance
- low ESR
- high pulse load capability
- low loss factor

In order to minimize self-inductance it is of importance to be able to install the capacitor as close as possible to the power semiconductor to be protected. Furthermore, a high mechanical stability is necessary due to the often rough environmental conditions existing in industrial applications.

Based on long experience with Polypropylene pulse capacitors in all conceivable applications, the series WIMA Snubber MKP and WIMA Snubber FKP were developed to meet the demands of high-power converter technology and are state-of-the-art components with regard to quality, reliability, and electrical performance. The WIMA Snubber technology is unique

Low-loss Polypropylene dielectric
High pulse load capability due to double-sided metallization or film/foil construction.
High voltage / overvoltage strength
Low-inductance design achieved by end-surface contacting
Various connection configurations.
Direct-contact terminals for safe contact at high continuous current load
Flame-retardant plastic case, UL 94 V-0

Production sites ISO 9001:2000 certified