A resistance module for increasing a runup torque for a rotor of an electric machine with a rotor winding includes first and second connection points, a plurality of electrically-conductive layers electrically connected to the first and second connection points. Each of the layers surrounds an axis of the resistance module at least partially in a circumferential direction and has a layer start point and a layer end point. At least one of the layers is configured in an undulating shape in the circumferential direction, with undulations projecting radially outwards. A first insulating layer is disposed between neighboring ones of the layers. The layer end point of one of the layers is electrically connected at a tie point to the layer start point of a neighboring one of the layers. At least one fastening element is disposed between two neighboring undulations in the circumferential direction and radially outside of the layers.

A synchronous motor assembly includes a motor connected between two nodes of an AC power source, a motor drive circuit, and a regulation unit. The drive circuit drives the motor to rotate. The regulation unit regulates a rotation speed of the motor via regulating the motor to different steady voltage points.

Systems, methods, and apparatuses include an alternating current (AC) contactor comprising a contactor coil, the AC contactor configured to selectively connect a power source to a motor, a controller power transformer (CPT) electrically connected to the contactor coil by a CPT switch, a resistor-inductor-capacitor (RLC) circuit electrically connected to the contactor coil by an RLC circuit switch, a voltage monitor electrically connected to the contactor coil to sense voltage across the contactor coil, and a switch controller to active the RLC circuit switch to selectively connect the RLC circuit to the contactor coil during a low-voltage event determined by the switch controller from voltage across the contactor coil sensed by the voltage monitor. The RLC circuit can discharge stored electrical energy to power the contactor. A second RLC circuit can be included in the apparatus and controllably discharged to extend the low-voltage ride-through.