Surge Capacitors

RC networks are used across the coils of the contactors, to protect them from the undesirable transient voltages that are generated during switching off of contactor coils. The induced transient voltage surges can be several times the rated voltage of the coil and can damage the coil of the contactor. These induced voltages also have a high frequency of the order of several KHz and generate noise.
RC networks connected in parallel to the coils of the contactors effectively suppress the surge voltages by absorbing the energy contained in the transients and safely discharging them. The RC networks also filter out the noise generated by the transients.