Design of a frameless torque motor

Abstract

The space industry has the ever increasing problem of the optimal utilization of all the volume inside the various spacecraft. Nearly every present day missile has an inertial guidance system which uses permanent magnet motors to compensate for friction loss in the moving parts. Since the space available for these motors is limited, the motor designer must obtain a design which will supply maximum torque for the available power input.

The designer must determine the optimum rotor outside diameter, magnet size, rotor stack length, slot size, and all other internal dimensions of the motor. Economics dictate that the engineer may work on a design for a given time only. At the end of this time he is forced to use his best design, without knowing whether it is the best one possible.

This investigation consists of the derivation of design equations for a permanent magnet direct current motor. The design procedure is programmed into a digital computer. The performance characteristics of each possible design, within practical limits, is calculated using an iteration process. The calculated performance data is compared with the actual test values from a similar motor.