Electrical switches have to pass many different tests during the approval phase. Some of these tests concern their switching behaviour under various test conditions. A switch is tested under nominal load, overload and with several values of cos phi (power factor). Besides continuous loading, switching on and off processes are also investigated. Throughout testing, it is crucial for the set parameters not to be altered. Air-cored inductors were used as inductive loads in the past, because they almost never saturate. Air-cored inductors are however larger and have a stronger leakage field than comparable iron-cored inductors with corresponding magnetic energy. In order to set the relevant cos phi (power factor) value, matched resistances must be connected up in addition. In order to meet all the required test points, many various inductive and ohmic loads must be available.

• Matched linearity to the application, so no saturation in the relevant working range
• Several tappings, so there amount of inductors can be reduced
• Matched winding resistance, therefore reduced number of external resistors
• Designed for continuous load and short-time loading
• Costs reduced by optimized weight and dimensions
• High nominal voltage, standard up to 1000 V

*Relevant norms: IEC 60669 und IEC 61058