9T18Y900G19 - 

The Volt-Pac variable transformer provides continuously adjustable voltage over a range of zero to either 100% or 117% of the line voltage. Its operation is simple and efficient, and is based on autotransformer action. The Volt-Pac coils are precision wound on a toroidally-shaped core. One face of the winding is properly smoothed and gold plated to provide a low resistance and long wearing track for the carbon brush. This plating process has been developed to provide efficient mating of brush and brush track for improved reliability of operation under severe operating conditions. Operating life has been substantially improved as a result. The core consists of strip-wound silicon steel for low electrical losses. The coil is insulated from the core by means of a molded phenolic form. To aid in heat dissipation a thermal radiator is mounted to, but electrically insulated from the shaft. This thermal radiator also serves as a brush holder.