Generally the motors which are commercially available deliver low torque at high speed and can not be used for driving the load directly. Gear reducers are used to increase the torque so as to meet the torque demand of the load . For servo application i.e. for positioning the load, the gear reducers should possess following characteristics.
The bi-directional reducers means that, the energy can be transferred from input to output as well as from output to input. During deceleration, the motor is forced to act like a generator, converting the kinetic energy of the load into electrical energy. The deceleration of the load is decided by the rate of consumption of the electrical energy produced. Planetary gear boxes meets this requirement and are hence used at the GMRT.