New phase technology replacement for potential relay controls

This paper describes a new phase sensitive technology for starting single phase capacitor-start induction motors. The technique measures the phase difference between the mains and start winding voltages. Our goal was to develop a replacement for voltage sensitive potential relays with only a few application choices that apply across a wide range of different motors. The new device adjusts to individual motor starting requirements and selects the optimum point to disconnect the start capacitor. This control uses a microcontroller for implementing the rule based control algorithm. Application of artificial intelligence through control rules provides the device with adaptability to different motors and loads. Also, the microcontroller and rules allow implementation of embedded diagnostics. This new class of controls is intended primarily for hermetic and semi-hermetic compressor applications. It can be applied to pump and ventilation applications as well