Two-step connection of electric motors by means of electromagnetic switches

摘要

A method and apparatus using electromagnetic switching in a two-step connection process is provided to minimize surge currents and torque oscillations in three-phase motors during starts.

主权项

1. A method of switching electrical contacts comprising:
monitoring voltage in an electrical system having a power source and a motor; closing first direct current electromagnetically controlled contacts at or before a first phase angle following a phase voltage zero-crossing such that current begins to flow in at least one winding at approximately the first phase angle following a phase voltage zero-crossing, the direct current electromagnetically controlled contacts configured to regulate power supplied to the motor by the power source; and thereafter closing remaining direct current electromagnetically controlled contacts at a prescribed moment following the closing of the first direct current electromagnetically controlled contacts.