Motor Insulation Material Development for Improved Power Density

Insulation systems for large, Brushless DC propulsion motors typically use Pulse Width Modulated (PWM) power converters with high frequency (>10KHz), high voltage switching for efficiency and control benefits but this places significant demands on the insulation system. Switching frequency, peak voltage amplitude and voltage rate of change (dv/dt) are key factors in the degradation of insulation life due to voltage stress, partial discharge, corona and other effects. Motor winding current losses affect insulation temperature and life as well. Motor wire, wire insulation, slot liner, inter phase separator and varnish form an insulation system that requires a balancing of many conflicting factors to successfully meet each applications unique requirements. For high power density machines thermal, and mechanical factors dictate thin insulation, counter to electrical and manufacturing desires for thick, robust insulation. SatCon proposes a spiral development effort, starting with this Phase I program which focus on the commercial application of improved insulation for large, PWM, PM machines. Activities include the identification of application requirements, selection of appropriate insulation system components, material testing, machine design; drive integration, system performance analysis, generation of accelerated life test procedures and equipment identification. Subsequent phases will address full scale laboratory model testing.