| 摘要 |
<p>A brushless motor has interconnected stator coils (21-26) and gate controlled solid state rectifiers (61-76) which are responsive to forced commutation below in particular rpm and self- commutation above said rpm and which selectively conduct current into and out of the junctions of the coils in dependence upon which of said rectifiers is operative. This produces stator poles which are angularly displaced from the poles (20) of the rotor (36) and which shift in position as the rotor rotates. Trigger assemblies (101-108) are provided for controlling the energization of the various gate electrodes, each said trigger assembly comprising a pick-up coil (110) forming a portion of a frequency selective circuit whose resonance frequency varies in dependence on the position of a rotating magnetic element (109). A sine wave oscillator (100) is coupled to the frequency selective circuits, the oscillator being operative to produce either of two different output frequencies, and an electronic switch (222) responsive to the rotor speed selectively changes the output frequency of the oscillator. One of these frequencies induces trigger assembly operation at all rotor positions and advanced SCR trigger timing for reliable starting and very low speed operation. The other frequency retards SCR trigger timing for most efficient motor running at moderate and high speeds. <IMAGE></p> |
