Detecting Multi Frequency Fault Currents
F-Type and B-Type RCDs are designed to detect residual currents with differential frequencies over the range of 10 hertz to 1000 hertz.
In the situation where we find several frequencies occurring at the same time on an installation, for example a load that is operating at 50 hertz, a motor controller that is operating at a lower frequency and invertors operating at higher frequencies, we could potentially have a residual fault current comprising of two or more frequency components. In such an instance a conventional RCD might see the power frequency fault current at 50 hertz but be unable to detect the fault currents at the other frequencies. It is not practical to use a conventional RCD to detect Multi Frequency fault currents. An F-Type RCD or a B Type RCD however will detect the various fault currents at different frequencies and at the power frequency of 50 or 60 hertz.
The application of the RCD, the type of installation that it will be fitted on and the equipment that it is intended to be used on needs to be carefully considered to ensure that the correct RCD technology is applied. At Western Automation we start with the application and work from there to ensure that we select the most suitable RCD technology for the given application.