This report investigates a method of selecting the optimum speed reduction ratio between motor
and load for d.c. servo drive systems under heavy external load conditions. The optimum reduction ratio is
determined to minimise heat dissipation in the armature coil of d.c. servo motors and, therefore, to enhance
the operating performance of the total servo system. In addition, based upon the optimum reduction ratio,
a strategy of selecting the best d.c. motor is discussed from the viewpoint of torque requirements of the
servo system. Finally, an example is illustrated to demonstrate how the optimum strategy can be applied to
actual design problems.