The invention provides a mobile environment-controlled unit having a chassis, a compartment supported by the chassis, and an environmental-control system in environmental communication with the compartment. The environmental-control system includes a multiphase alternator powered by an internal combustion engine and supplies electrical power for the environmental-control system. The alternator has a first phase winding to generate a first high-voltage alternating phase current and a second phase winding to generate a second high-voltage alternating phase current. The environmental-control system further includes a magnetic sensor including a core, and a magnetic sensing device interconnected to the core and providing an output based on a sensed electromagnetic parameter.