High-frequency portable tools and equipment

This paper presents practical information regarding the application of high-frequency (180-cycle) induction motors with low-resistance rotors to portable electric tools. In order to compete with existing tools it became necessary to increase the rotor speed above 60 cycles, and 180 cycles per second was adopted as commercially practical. Several advantages are shown. Due to a smaller drop in speed with this type of motor than with the direct current and the universal motor, greater power is developed. Because of better speed regulation the life of the cutting tools is longer. Less weight and lower maintenance costs result from this application. Several new tools for special work are described. The desirable regulation of the frequency converter or motor-generator is given as not exceeding 8 per cent.