Electricity: motive power systems – Switched reluctance motor commutation control
Patent
1997-07-11
1999-08-03
Sircus, Brian
Electricity: motive power systems
Switched reluctance motor commutation control
318439, 318270, 318380, 388811, H01R 3946
Patent
active
059329793
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a DC elevator, and more particularly, to a pulse width modulation (PWM) speed-control apparatus for controlling the speed of DC elevator.
BACKGROUND OF THE INVENTION
Presently, there are two kinds of conventional speed-control systems for a DC elevator, one of which is a generator-motor speed-control system excited with a silicon controlled rectifier (SCR), another is a SCR-motor speed-control system powered directly by a SCR. The elevator with the former speed-control system has some drawbacks, such as higher exhausted energy, larger room occupied by the elevator, higher noise, lower response speed and higher cost. The latter speed-control system has higher pulsating current and higher ripple torque, and its current is intermittent when the speed of elevator is low, because it is directly powered with the regulated voltage by SCR from an AC power supply. It is difficult to satisfy a passenger's comfort requirements so that its application to an elevator is limited. Furthermore, there are other drawbacks e.g., it has a lower power factor and needs larger-volume smoothing inductors and loop reactors etc.
SUMMARY OF THE INVENTION
The object of the invention is to provide a PWM speed-control apparatus for a DC elevator, which makes use of a microcomputer to create acceleration curve and deceleration curve, adjust its running process, and control its running state. The pulses for measuring speed and distance are produced by a photoelectric shaft encoder. The chopper voltage regulation is accomplished by PWM with fully controllable power electronic components.
Another object of the invention is to provide a DC elevator using the above-mentioned PWM speed-control apparatus for a DC elevator.
To achieve the objects, the invention provides a PWM speed-control apparatus for DC elevator, comprising a rectifier-filter for rectifying and filtering the power from AC power supply to convert it into DC power; a pump-rising voltage suppressor, connected between the DC output terminals of the rectifier-filter, for preventing over-voltage between the DC output terminals in a braking process of a motor; a chopper voltage regulator, having input terminals connected across the output terminals of the rectifier-filter and output terminals connected to an armature of a DC motor serving as major-governor, for converting the DC output voltage of the rectifier-filter into a controlled DC output voltage by PWM and supplying the controlled DC output voltage to the armature of the DC motor to control the rotating speed of the DC motor; a system controller receiving a pulse signal proportional to rotating speed of the DC motor from a photoelectric shaft encoder connected to the rotor of the DC motor to produce a PWM signal in response to a difference between an actual rotating speed and a setting speed of the DC motor; a driving protector receiving the PWM signal from the system controller to produce a control signal for driving the chopper voltage regulator; a current sensor for detecting an armature current of the DC motor to provide a current feedback signal to the system controller.
The invention further provides a DC elevator using the above-mentioned PWM speed-control apparatus for DC elevator.
The above object and features of the invention will be more apparent through the description of the preferred embodiments of the invention with reference to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
FIG. 1 is a schematic block diagram of a preferred embodiment of the PWM speed-control apparatus for DC elevator of the invention,
FIG. 2 is a working flow chart of the preferred embodiment of the PWM speed-control apparatus for DC elevator of the invention,
FIG. 3 is a circuit diagram of the preferred embodiment of the PWM speed-co
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