Evaluation of Relay Suppression Circuits for Reducing EMI

The objective of the work described in this paper is to make a comparison of various suppression circuits, connected across the relay, for reducing electromagnetic interference, considering also the effect of relay armature release time (dropout delay time). Tested suppression circuits described in this paper are diode, diode with Zener diode (two cases with different Zener voltages), diode with resistor, and capacitor. Radiated and conducted noises were measured at frequencies up to 1 MHz. Experimental data, supporting analysis and conclusions are presented