Enterprising Engineers

Grid Resistance Starter is for starting the Slip Ring Induction Motor.
Metallic resistance elements made up of Stainless Steel (S.S.), either in the form of Punched Grid type or Coil type are used to provide the required resistance in the rotor circuit. These resistance elements are skillfully fabricated and designed for continuous rating to suit the motor parameters.
The steps are selected adequately for precise speed control, to increases / decrease the speed linearly as to avoid large current kicks. Speed variation between each steps are restricted 1% to 2.5% (or as required by the customer). Different tapping from the resistance element through the power shorting contactors are taken to design these steps.
With the help of PLC logic the power shorting contactors are turned off/on enabling to reach the desired speed. Cooling blowers are provided in the resistance chamber to remove the heat getting generated. It helps in controlling the change in resistivity of the element with temperature rise and increases the life of the resistance elements.