Waste heat energy conversion cycles, systems and devices use multiple waste heat exchangers arranged in series in a waste heat stream, and multiple thermodynamic cycles run in parallel with the waste heat exchangers in order to maximize thermal energy extraction from the waste heat stream by a working fluid. The magnetic excitation part supplies a magnetic flux to a magnetic salient pole. The physical keying system prevents a user from connecting a host device to a connector of the power source which does not support that host device. The plunger is movable relative to the switch housing between a non-actuating position and an actuating position.