摘要:
A load control device is adapted to be disposed in series with an AC voltage source and an electrical load and is operable to provide substantially all voltage provided by the AC voltage source to the load. The load control device comprises a controllably conductive device, a controller, a zero-crossing detector, and a power supply for generating a substantially DC voltage for powering the controller. The power supply is operable to charge an energy storage device to a predetermined amount of energy each half-cycle. The controller is operable to determine when the power supply has stopped charging from the zero-crossing detector each half-cycle, and to immediately render the controllably conductive device conductive to conduct the full load current. Before the controllably conductive device begins to conduct each half-cycle, only a minimal voltage develops across the power supply to allow the energy storage device to charge.
摘要:
A power supply for a load control device is disposed in series with an AC voltage source and a load and generates a substantially DC voltage for powering a controller of the load control device. The power supply is operable to provide substantially all voltage provided by the AC voltage source to the load and includes a controllably conductive device, a triggering device, and a charging circuit. The charging circuit is operable to charge an energy storage device and to conduct current to the load when the controllably conductive device is non-conductive. The controllably conductive device begins conducting the full load current when the energy storage device has charged to a predetermined amount of energy. Before the controllably conductive device begins to conduct, only a minimal voltage, which is substantially the same as the break-over voltage of the triggering circuit, develops across the power supply to allow the energy storage device to charge.
摘要:
An AC motor speed controller includes a plurality of capacitors that may be selectively switched, by means of controllably conductive switches, into series electrical connection with an AC motor and an AC voltage source to control the speed of the motor. To change the speed of the motor, a control circuit renders a first switch conductive, in response to a first detected AC voltage zero crossing, to charge a first capacitor to a predetermined voltage. The control circuit then renders a second switch conductive, in response to a subsequent second detected AC voltage zero crossing, to charge a second capacitor to the predetermined voltage. The control circuit then renders both switches simultaneously conductive at a predetermined time after a subsequent third detected AC voltage zero crossing. The capacitors will thereby be charged to the same voltage prior to being switched into series with the motor, thereby resulting in reduced acoustic noise when changing motor speeds.
摘要:
An apparatus for controlling the speed of an AC motor comprising a switch adapted to be coupled in parallel with power terminals for the AC motor; a capacitor coupled in series with the parallel combination of the switch and the motor; the capacitor adapted to provide an AC supply voltage from an AC source to the parallel circuit comprising the motor and the switch; and a control circuit for controlling the conduction time of the switch in order to vary the speed of the motor. The switch is preferably pulse-width modulated at a frequency twice the line frequency of the AC supply voltage, and the switch is turned on when the voltage across the AC motor is zero volts. The apparatus is operable to provide for continuously variable control of the motor speed while minimizing acoustic noise in the motor.
摘要:
A load control system for controlling the amount of power delivered to an electrical load from an AC power source includes a load control device and a remote control device. The load control device is operable to control the amount of power delivered to the electrical load in response to control signals transmitted by the remote control device. The remote control device may transmit the control signals to the load control device via current carrier control signals, radio-frequency control signals, or infrared control signals, which may be corrupted by noise during transmission. The received control signals are sampled and filtered by a multi-pass median filter, which substantially eliminates the noise corruption. Specifically, the multi-pass median filter repeatedly examines a set of N sequential samples of the received message signal, determines the median of the N sequential samples, and provides the median as an output sample.
摘要:
An apparatus for generating a fluid flow is disclosed that circulates a plurality of spaced blades or airfoils attached to one or more drive belts about two or more spaced rotatable members. Each blade is commonly journalled with another blade. The inclination angles of each blade and each commonly journalled blade are independently controlled by a control mechanism.
摘要:
An adaptor for attachment to the end of a rifle allows an individual to f from the rifle a different projectile than originally designed for the rifle, without substantial degredation in overall accuracy and throw distance of the rifle. The adaptor has a rifled cylinder which in the typical application will have progressive twist rifling. The tangential force acting upon the projectile within the progressive twist rifling area has a semi-elliptical shape and an exit value of approximately zero. An adaptor ring and outer shell are preferably employed to mount the rifled cylinder to the rifle and for aligning the adaptor axis and rifling with the rifle barrel axis and rifling.