One way to envision what is happening in an AC-to-DC rotary converter is to imagine a rotary reversing switch that is being driven at a speed that is synchronous with the power line. Such a switch could rectify the AC input waveform with no magnetic components at all save those driving the switch. The rotary converter is somewhat more complex than this trivial case because it delivers near-DC rather than the pulsating DC that would result from just the reversing switch, but the analogy may be helpful in understanding how the rotary converter avoids transforming all of the energy from electrical to mechanical and back to electrical.