While the fundamental frequency is allowed to pass through by using capacitors and inductors, the harmonic frequencies are diverted to a filter resistor which perform the role of dissipating these harmonic current as heat.

There are many parameters that need to be considered in the design of filter resistors. Some of the key parameters include:

• Power dissipation from the resistors as heat, through the use of appropriate cooling mechanisms
• Resistance value and required tolerance computed for the specific circuit and application characteristics
• Standard Line Voltage, Insulation class, expected voltage transients, arcing and creepage distances to accurately design the filter resistor
• Current rating computed based on the nominal rated current and the peak transient current during startup

Filter resistors are used in:

• Power systems with non-linear loads
• HVDC Converter Stations
• Oil and gas substations

Network quality and safety, reduction of the reactive power and requirements regarding the reliability of assemblies and components have been increasing in significance for years. With the help of filter circuits, it is possible to counteract these undesirable effects.

KWK supplies filter resistors for passive RLC filter circuits with resistances of just a few watts and with compact dimensions, for use in device assemblies, e.g. as overvoltage protection, and ranging right up to complete, several kilowatt filter systems for medium voltage application.

Since filter resistors have to be designed specifically for the end application, we work closely alongside the customers.