Unique EMC filters minimise earth leakage currents

TDK Corporationhas re-engineered and improved the EPCOS LeaXield active leakage current filter, a unique solution that can minimize earth leakage currents in converter-based drive systems. The device is intended for applications in variable-speed drives such as those in machine tools, compressors, pumps, conveyance systems, and other pluggable devices. In these systems, aggregate earth leakage currents may cause RCDs to trip at their threshold. As a result, RCDs are not usable or only with substantial extra outlay. The device is offered for load currents of up to 50A at a rated frequency of 50/60Hz and phase-to-phase voltages of up to 520VAC. The active leakage current filter is joined between the RCD and the EMC input filter of the converter in industry-standard three-phase TN power grids. It does not need an extra power supply. The device can be employed for earth leakage currents of up to 1A and can efficiently compensate leakage currents over a broad spectral range from 150Hz to approximately 30kHz. The device couples a 180-degree phase-shifted current with the same amplitude to the leakage current to the respective phases and feeds it backwards to the source. This stops the leakage currents from flowing through the RCD and tripping it inadvertently, thus enhancing plant availability. Thanks to its compact design, the device is also ideal for retrofitting existing installations. As no external power supply is needed and installation expense is minimal.