| 摘要 |
<p>A fire door opener or operator (10) according to the invention includes a DC brake solenoid (632) coupled to an AC motor drive system (12) with an inline gear reducer. If AC power is lost, the brake can be controlled by an electronically controlled descent device and the battery backup power. If the brake is disengaged, the door (20) will drop by overcoming the internal inertia and friction in the inline gear reducer. A method for electronically controlling the descent speed of a fire door with or without AC power or motor control is also described. Speed of descent is controlled electronically by measuring the descent speed of the fire door (20) at its limit shaft and electrically modulating the brake engagement using the DC solenoid (632). <IMAGE></p> |
