The U.S. Bureau of Mines has, for the past 2 years, been investigating the early detection of insulation failure in squirrel cage induction motors using sophisticated empirical data modeling techniques based on engineering values calculated from the motor line voltage and line current phasors. The research has now progressed sufficiently to design and build a prototype system that simultaneously monitors six motors on a continuous miner. This prototype system consists of a single-board computer-based motor monitor for each motor. Each motor monitor is connected through a parallel interface to the bitbus digital i/o board. The control computer regularly requests, through bitbus, a set of three-phase line voltage and line current phasors from each motor monitor, from which it calculates two deterioration values for the motor, one for fault current and one for fault power. An alarm sounds if any value exceeds a preset deterioration threshold. While this motor monitoring is taking place, the system can also display the deterioration history of any motor or display and change system parameters.