NI SCXI-1163R Contact Protection for Inductive Load Connections

When inductive loads are connected to the solid-state relays, a large counter-electromotive force can occur at relay switching time because of the energy stored in the inductive load. These flyback voltages can severely damage the relays.

It is best to limit these flyback voltages at your inductive load by installing, across your inductive load, a flyback diode for DC loads or a metal oxide varistor (MOV) for AC loads. Refer to the following figures for these two configurations:

Contact Protection for DC Inductive Loads

Contact Protection for AC Inductive Loads