Abstract: The present invention is directed to a method and apparatus for connecting a static inverter to a free-running motor, wherein the inverter is supplied with D.C. power by a regulator-controlled rectifier. An oscillator connected to both the rectifier regulator and the inverter governs the frequency of the three-phase inverter output, while voltage feedback from the inverter output to the rectifier regulator is employed to establish a proper volts/hertz output characteristic in the inverter output waveform. During the connection process, a synchronizing circuit causes the oscillator to generate a high pulse rate signal which raises the inverter output frequency to a level above that associated with the rotational speed of the free-running motor. Simultaneously, the D.C. output of the rectifier is clamped by the current regulator to current-limit the inverter output. The inverter is subsequently connected to the free-running motor and the inverter output frequency is allowed to decrease gradually.
October 1, 1981
Date of Patent:
August 15, 1989
Emerson Electric Co.
James Maurice, David J. Collins, Michael O. Hall, Peter D. McLoughlin
Abstract: A method and apparatus of variable structure for controlling asynchronous motors. More particularly, methods and apparatus for control of flux, torque, angular acceleration, angular velocity, and/or angular position of the rotor of an asynchronous motor, supplied through a converter having switched elements.
Abstract: The optical density pattern of an original document (26) is sensed during scanning movement for radiating a light image of the document (26) onto a photoconductive belt (27) which is held stationary during the scanning. Operating parameters of the apparatus (21) which are to be controlled after completion of scanning are computed as functions of the sensed pattern. Copy sheets of different sizes are provided, and the copy sheet size is selected to be equal to the sensed width of the document (26). Illumination lamps (37) are selectively energized to discharge non-image portions of the belt (27) between scanning and developing in accordance with the sensed dimensions of the document (26). A developing bias voltage is controlled in accordance with sensed document density and contrast.
Abstract: A link regulator is disclosed for providing a regulated voltage over a wide range of input frequencies and load currents. The frequency of an internal VCO and the input frequency are phase compared to provide a reference error signal. The unregulated DC voltage is integrated for a duration proportional to the error signal. This duration controls a series switching element to provide a constant volts/seconds. The output of the series switching element is filtered to a DC voltage that controls the frequency of the VCO. The DC voltage is proportional to the error signal, thus providing a feed forward system to regulate the DC voltage. During the period when the series switching element is not conducting, a shunt switch presents a low impedance to the input of the filter to clamp the input to ground. This allows for operation over a wide range of load currents without losing regulation.
Abstract: A "mode switch" is used for smoothly switching a servovalve controlled device such as an SMC press, in particular, from control under one parameter to control by another. The mode switch provides a very smooth transfer of control from displacement control between two relatively movable parts to force control to provide for controlling the force exerted by actuators acting between the two parts. The mode switch electronically tracks the signals so that when the switching is made the signals are precisely equal to prevent abrupt changes in the control signals. This smooth transfer is achieved even under active control, that is when both control signals are changing in value.
Abstract: Disclosed is a rotary machine powered by magnetic fields and comprises at least one fixed and at least one movable permanent magnetic member which have a curvilinear surface adapted to provide mutually eccentric magnetic fields and which operate to rotate the movable member with respect to the fixed member until a magnetic equilibrium position is reached, at which time means are included to rotate the movable member away from the equilibrium position, whereupon the eccentric fields again interact to cause rotation. The curvilinear surfaces are in the form of a spiral which expand in an arithmetic or geometric progression and are poled to provide alternatively either attractive or repulsive forces between opposing faces of the magnetic members.
Abstract: A clamping tracer control system which performs a tracing feed and a pick feed alternately and effects a clamping feed at a preset clamp level and in which, between the pick feed position where the clamping feed is carried out first and the pick feed position where the clamping feed has been completed, tracer control is repeated while changing the clamp level sequentially, and when the clamping feed has been completed in the repeated tracer control, the clamp level is restored to its area of initial value to resume tracer control of the tracing feed and the pick feed alternately in the next area.
Abstract: An electronically controlled rotating synchronous machine having armature and field windings on the same magnetically-permeable core. The rotor of the machine is an open tooth structure. The self inductance of the armature and field windings is substantially independent of relative position between the rotor and stator but mutual inductance between the armature and field windings varies with relative position. A rotor position detector senses the voltage in one of the machine windings and relates that voltage to said relative position. Switches are provided to control electric current flow in the armature winding on the basis of the voltage sensed by the detector.
Abstract: An improvement is disclosed in which a circuit utilizes the internal resistance or bulk resistance of a Hall generator in connection with an amplifier having a feedback resistance which is less or larger than the internal resistance or bulk resistance of the Hall generator. By utilizing this improvement, changes in output voltage of the Hall generator caused by variations in temperature and spread in characteristics can be at least partially compensated.
Abstract: A circuit for controlling the energization of an electrical load from an AC source. The circuit has a pair of DC lines, and means is provided for rectifying the AC output of the source to apply a DC voltage across the DC lines in the form of a full wave rectified sinusoidal signal. Signal switching means for connection between the DC lines and the load establishes a conductive path therebetween during a variable time interval when the voltage applied by the full wave rectified sinusoidal signal exceeds the voltage across the load, and means including the switching means is provided for chopping the full wave rectified sinusoidal signal to apply pulses to the load during the variable time interval at a frequency which is high with respect to the frequency of the signal.
Abstract: A motor control circuit utilizes sample and hold circuitry whose operation is initiated by an analog switch to control the firing angle of silicon control rectifiers, thereby to minimize wasting of power supplied to the motor being controlled.
Abstract: The invention relates to an inverter circuit for operating a speed-controllable asynchronous motor. The inverter circuit is of the type wherein the voltage and frequency are substantially proportional until the nominal frequency has been reached at nominal voltage. The circuit includes and inverter, a desired value control, a D.C. voltage supply with a voltage regulator which sets the voltage depending on the desired value, and a voltage-operated frequency regulator. The circuit can be operated at frequencies above the nominal frequency to avoid damage to the inverter which would otherwise be caused by (1) high voltage due to the motor operating as a generator or by (2) the rapid reduction of the speed setting controls which is not accompanied by a corresponding drop in the voltage supplied to the inverter.
Abstract: A pulse generating system for providing firing pulses to selectively trigger solid state control devices connected to a three-phase A.C. line system, and more specifically to trigger said devices in selected relation with respect to the phase and frequency of the A.C. line.
Abstract: Stabilized operation of an inverter and an a-c motor, driven by the inverter, is obtained in the presence of sudden undesired load changes by controlling the inverter so that both the amplitude and frequency of the inverter output a-c voltage will be functions of, and will vary directly with, the d-c bus voltage, with the result that anytime an abrupt abnormal load change causes the d-c bus voltage to vary, a frequency change occurs to compensate for the load change and to stabilize the bus voltage. By employing the d-c bus voltage to regulate the inverter frequency, if there is a sudden decrease, for example, in the mechanical load on the motor, the d-c bus voltage, which will tend to increase, causes the frequency of the inverter output voltage to increase, thereby increasing the motor speed so that the electrical load change across the d-c bus is reduced. As a result, the d-c bus voltage tends to remain relatively constant in spite of the abrupt mechanical load change.
Abstract: A power control circuit for a three phase induction motor wherein power factors for the three phases are summed to provide a control signal, and this control signal is particularly filtered and then employed to control the duty cycle of each phase of input power to the motor.
March 14, 1983
Date of Patent:
February 21, 1984
The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
Abstract: A three-dimensional tracer control system which is provided with an integration circuit for integrating the difference between a Z-axis direction displacement signal and a reference displacement signal and an adder for adding together the above-mentioned difference and the output from the integration circuit. The trace velocity in the Z-axis direction is controlled by the output from the adder, by which it is possible to perform tracing, with the Z-axis direction displacement signal and the reference displacement signal held nearly equal to each other; consequently, machining accuracy is increased.
Abstract: A drafting machine which employs two variable speed and one constant speed motors. A pencil is moved along both X- and Y-axes by means responsive to the speed differentials of the motors. Speeds of the motors are controlled by an electrical circuit having a plurality of off-on switches and a plurality of rocking switches. The latter load counters from a pulse generator into counters for straight line, circle, spiral and logarithmic spiral controls which control activation of resistors which govern the speeds of the two variable speed motors. Indicators indicate to the operator the direction in which the pencil is moving, the diameter of a circle being drawn, the increment (or decrement) of a spiral being drawn as compared with a circle and the increment (or decrement) of a logarithmic spiral being drawn as compared with a spiral.
Abstract: A control for an A.C. motor operates to feed a high average value of voltage to the motor during a starting period of predetermined duration and to then automatically switch the voltage supplied the motor to a lower average voltage of substantially fixed value. This lower value of average voltage is determined without feedback to the control circuit. The control may be designed for use with single phase or multiple phase motors and for motors of various different power ratings.
Abstract: A DC motor control apparatus is disclosed comprising a first pair of switching elements coupled respectively with oppositely poled ends of the DC motor. A first actuating means is provided for actuating one of a first pair of switching elements in response to an input signal of a first predetermined logic content. The other of the first pair of switching elements is provided to respond to an input signal of a second predetermined logic content. Also provided, are means for applying a driving potential to the oppositely poled end of a motor simultaneously with the actuation of each of the first pair of switching elements, thereby establishing a current path for forward direction and reverse direction operation of said DC motor, respectively. A second pair of switching elements are respectively connected to oppositely poled ends of the DC motor.
Abstract: Device for the attenuation of the movement of the reel motors in recording devices during standstill of the tape capstan drive roller. The regulation of the reel motors proceeds during the normal run of the tape via the motor current and during the standstill of the capstan drive via the voltage which lies at the reel motors.