Emergency capacitive energy source and circuit for damper motors and

Abstract

The emergency, fail safe capacitive energy source and circuit is used in conjunction with an air damper actuator or a valve actuator. In particular, the capacitive energy source and circuit powers a fractional horsepower motor and both the motor as well as the capacitive energy source and circuit are completely contained within an actuator container of a relatively small size. The capacitive energy source and circuit include at least one high storage capacitor (rated 0.047 farads or higher) having a volumetric size not exceeding 30 cubic inches. Preferably, a bank of high value capacitors are utilized wherein the capacitors are coupled in series or parallel to power the AC or DC motor and associated circuitry. The capacitive energy source and circuit also includes a charging circuit coupled between the motor drive power source and the capacitor or bank of capacitors. A sensor is coupled to the motor drive power source and generates a control signal in the absence of power from the motor drive power source. A switch, controlled by the control signal, is coupled to the motor drive power source and is also coupled to the capacitor or bank of capacitors. The switch has a switched output coupled to the motor. The switch passes power from the motor drive power source to the motor in the absence of the control signal from the sensor and passes power from the capacitor or bank of capacitors in the presence of the control signal. In a preferred embodiment, the sensor is a coil of DC operated relay and the switch embodied by the relay contacts and is actuated by the relay coil.