A fluid feed stream is flowed, subject to electromagnetic pulses, to a filter element via an input feed conduit for the filter element. A coil assembly is disposed about the input feed conduit and an AC power source is connected with the coil assembly. The AC power source has a period including first and second half-cycles of opposing polarities. A switch in series with the coil assembly forms a series connected circuit. A second switch connected with the coil assembly forms a second circuit. A control means closes the first switch and opens the second switch during a first half-cycle of the AC power source. During a second half-cycle, the control means closes and then opens the second switch to produce a first large ringing pulse in the coil assembly. A subsequent pulse may be produced either before or after the first pulse substantially decays.