Application of a radio frequency antenna technique for monitoring the speed, torque and internal fault conditions of A.C. and D.C. electric motors

This paper describes a novel radio frequency (R.F.) measurement technique which can be used to measure the speed of rotation and the torque developed by a mechanically commutated DC electric motor. It also has the potential to detect fault conditions within the motor. The measuring instrument is a specifically designed radio antenna which detects the flux variations and R.F. signals associated with the partial discharges or arcing events present during commutation. Basic commutation and the factors influencing the partial discharge or arcing activity are described, followed by examples of the signals received and measurement results.