Abstract: The invention relates generally to optoelectronic pnpn devices and more particularly to a layer structure suitable for fast electrical complete turn-off of such devices and to a method for efficient and fast operation of such devices and differential pairs of such devices. The devices have four layers and three junctions, and the invention provides for complete depletion of both center layers. The differential pair of pnpn devices also provides a very sensitive optical receiver which combines a very high cycle frequency with a very high optical sensitivity.

Abstract: Disclosed are a method for the analysis of a sample by sputtering, using a particle beam, and a device to implement this method. The method consists in:scanning the sample on a surface called a scanning surface, to hollow out a crater with a flat bed, said flat bed constituting a surface called a surface of analysis;ionizing the particles liberated from the surface of analysis, by means of a pulsed laser beamidentifying the nature of the liberated and ionized particles by means of a mass spectrometer. The idle time available between two pulses of the laser beam is used to sputter the flanks of the crater, for these flanks also have to be sputtered although they do not form part of the surface of analysis proper. Thus the time needed to sputter the sample up to a certain depth is reduced to the minimum without loss of information.

Abstract: A method of measuring induction motor parameters so that the speed and torque control of an induction motor controller may be optimized. While the motor is stopped, a test signal made up of a current pulse of a known amplitude is applied to one or more windings of the motor stator for a selected period of time, after which the current pulse is turned off. After a short delay, the instanteous voltage across the stator windings is measured, and also an integration of the stator voltage is started which continues long enough so that the stator voltage decays to substantially zero. The measured voltage and integrated voltage are respectively proportional to the rotor resistance and the motor magnetizing inductance.

Abstract: An AC motor drive includes a power converter which supplies current to a DC bus from three-phase power lines. An inverter drives the motor from power delivered to the DC bus and it regenerates power to the DC bus when the motor is decelerated. The power converter in turn regenerates the power to the power lines by controlling line current such that it is substantially in-phase with the applied line voltages. Current overload protection is provided for the transistor switches employed in the power converter bridge circuit.

Abstract: A fume hood controller system in which the sash position is monitored by a transducer which provides a signal indicative of the area of the hood opening. A variable speed controller responsive to the sash position signal to provides a fan speed which varies as a function of the sash opening. An optional circuit monitors the power drawn by the motor and compares the actual power drawn by the motor with the expected power for the present sash position. If the actual power falls below the threshold, an alarm signal is generated indicating a reduced air flow in the fume hood. Additionally, motor overload may be detected by comparing the motor speed control signal with the actual motor speed. An alternate embodiment is shown in which the present invention may be used to control a single blower which exhausts a plurality of fume hoods while maintaining a substantially constant face velocity in each hood.

Abstract: A microprocessor-based motor control system operates the rapid advance motor on a slide transfer machine to carry out rapid traverse motions in minimal time. A velocity profile is stored during the acceleration portion of the move and this data is employed to determine when deceleration should begin and to control velocity during the deceleration portion of the move. A position feedback circuit having programmable resolution is employed to develop the velocity profile.

Abstract: The present invention generates a motor slip frequency value and two current magnitude values representing quadrature components of the motor stator current to be generated. Closed-loop control of the motor operation is provided by feeding back a signal representative of the motor shaft speed or position calculate the torque required from the motor. The feedback signal is separated into high and low frequency components. Additional circuitry changes the value in response to detected variations in the high frequency components of the feedback signal. The addition of this circuitry causes the motor control circuit to no longer represent the inverse of the motor transfer function network.

Abstract: A PWM, controlled current, voltage source inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexer are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.

Abstract: A transducerless brushless permanent magnet motor in which a signal induced by the rotor in an unexcited winding is used to sense the rotor position. The sensed voltage, induced in the winding by the rotor, is integrated to provide a representation of the magnetic flux coupling the rotor and winding. Before start-up, both the rotor position and the integrator are initialized to align the circuit representation of the flux with the actual flux.In an additional embodiment of the invention, a self-initialization circuit is provided to automatically preset the rotor and flux integrator to pre-determined and corresponding values.

Abstract: An inverter controls an induction motor in response to signals from a power factor control circuit. The power factor control circuit receives signals related to motor terminal voltages and multiplexes them to a comparator. The inverter and multiplexor are sequenced each time the comparator input reaches a reference level. The frequency of the inverter is thus self generated. The power factor of the system can be controlled to implement a variety of control strategies.