Start-control resistors (resistor boxes) are included in the electric motor rotor circuit. They are intended for smooth start, adjustment of speed and braking of electric motors of direct or alternate current operating in the electric drives of load lifting cranes.
In electric engines where the short-circuit rotor motors are applied, start-control resistors can be included in the stator circuit to limit the starting current and provide running smoothness of the mechanism.
Resistor boxes are a group of resistors connected electrically as per the predetermined pattern and fitted with contact clips for joining with the electric circuit, where the resistor is a node of an electric apparatus designed for electric energy absorption by turning it into the thermal energy and for limitation of current in the circuit. It is manufactured of high-resistance metal.