Resistance boxes are used to add resistance in to an electric motor circuit for modifying the performance characteristic of slipring induction motors of EOT cranes, rubber mills, steel rolling mills, cement mills, power plants, conveyors, coke oven, blowers etc. The basic types of resistors are stainless steel ( grade – 304) and punched steel resistors. Resistors are designed to meet requirements of both A.C. & D.C. applications. These are manufactured for current rating from 10 to 800 amps. Continuous resistors of higher ratings are manufactured using 2 or more parallel paths. Resistors with short time rating up to 3000 amps or even more for neutral earthling are possible which suitable for system voltage upto 11 kv and above. For speed control and developing starting torque with low starting currents. They are also used as Dynamic braking resistor for V.V.V.V.F.A.C. Drives, electric loading of ac alternators, degenerators and dynamometers.