Abstract: The active permanent magnet suspension (APMS) is presented and reviewed as a suitable means for laboratory and industrial realisation of non-contacting devices. Static and dynamic properties of axial and radial APMS rotary systems are discussed. A gas friction detector and a molecular beam chopper are described as typical scientific instrument applications.

Abstract: A chopper and a series circuit of a dynamic braking resistor and a thyristor are connected in parallel with a d.c. motor which is operated as a generator during braking operation. A series circuit of a diode and an inductance element is connected in series with the d.c. motor. A condenser connected between the ground and the junction of the inductance element and the diode forms a filter circuit together with the inductance element. Current generated by the d.c. motor flows into a d.c. source through the diode and the inductance element during regenerative braking operation. An over-voltage detector fires the braking thyristor when the voltage across the condenser becomes greater than a predetermined limit value, as a result the dynamic braking operation is performed. A chopper controller varies the interval between an ON pulse to turn the chopper into ON state and an OFF pulse to turn the chopper into OFF state for adjusting ON time and OFF time of the chopper in response to the current through the d.c. motor. An operation changer provides a signal to an automatic phase shifter to extend the interval between the ON and OFF pulses to a predetermined period of time enough to quench the braking thyristor when the braking operation of said d.c. motor is changed from the dynamic braking operation to the regenerative braking operation.

Abstract: When a power conversion apparatus such as inverter or chopper comprises gate turn-off thyristors (GTO's), current limiting reactors are connected to cathodes of the GTO's and opposite ends of each of the reactors are connected to positive and negative terminals, respectively, of a gate power supply which supplies a turn-on current and a turn-off current to the respective GTO. With this arrangement, an energy stored in each of the reactors at the turn-off of the GTO is absorbed by the gate power supply.

Abstract: A microwave oven is provided with a turntable for turning food and a radiation detection device for detecting radiation emitted from food without making contact with it so as to control its temperature. The radiation detecting device includes a radiation detector and a scanning reflecting mirror which linearly scans the turntable diametrically thereof and re-directs a beam of radiation through a chopper to the radiation detector. Because of the composition of the rotation of the turntable and the scanning movement of the reflecting mirror and of the chopper, a temperature at a very small spot on food may be detected so that regardless of the kind, shape and volume of food on the turntable, the temperature of food may be always detected with a higher degree of accuracy.

Abstract: A laser beam from a tunable laser is split into two paths containing an etalon and a sample cell respectively. The two paths are chopped at different frequencies. The paths are combined and fed to a monochromator and then detected by a single detector. Lock-in amplifiers tuned to the chopper frequencies and responsive to the detector output produce signals corresponding to the spectra arising from the etalon and the sample gas absorption. A recorder simultaneously displays the two spectra.

Abstract: Four radiant energy detectors are arranged in a common plane in a substantially square configuration with each detector occupying a separate quadrant. Infra-red energy received from a target is focused onto the detectors by means of a lens, there being a chopper positioned between the lens and the detectors to chop the radiant energy in a periodic fashion. The outputs of diagonally opposite pairs of detectors are each directly fed to a separate differencing amplifier, where difference signals are generated. These difference signals are then added together and subtracted from each other in separate circuits in a predetermined manner to produce a first signal representing the departure in azimuth of the target from a reference axis running through the center of the detector array, and a second signal representing the departure in elevation of the target from this same axis. The azimuth and elevation signals are separately phase detected in phase detectors which are referenced to the chopper drive signal, the outputs of the phase detectors being filtered in low pass filters to produce DC signals representing the departure in azimuth and elevation of the target from the reference axis. These signals can be fed to an indicator or employed to drive a servo system which slews the support structure for the detectors so as to lock the detectors onto the target.

Abstract: A novel control scheme is investigated for operating induction motors in the constant torque mode. The basic control schemes and analysis of the steady-state performance of the system are presented. Circuit models are used to predict the performance characteristics. A new dc dynamic braking method is proposed and studied that provides very fast braking. Experimental results are presented to verify the theoretical predictions and demonstrate the feasibility of the control schemes.

Abstract: A laser beam apparatus and method for analyzing, inter alia, the current versus voltage curve at the point of illumination on a solar cell and the open circuit voltage of a solar cell. The apparatus incorporates a lock-in amplifier, and a laser beam light chopper which permits the measurement of the AC current of the solar cell at an applied DC voltage at the position on the solar cell where the cell is illuminated and a feedback scheme which permits the direct scanning measurements of the open circuit voltage. The accuracy of the measurement is a function of the intensity and wavelength of the laser light with respect to the intensity and wavelength distribution of sunlight and the percentage the dark current is at the open circuit voltage to the short circuit current of the solar cell.

Abstract: FAST neutron choppers have been considerably developed in the past few years. The commonly used choppers are either rotating massive objects through which appropriately shaped neutron channels are cut1 or crystals whose diffracting power may be modulated by magnetic fields2 or dynamic strains3. All these devices suffer from practical limitations of speed, poor duty cycle and the consequent loss of intensity. We describe here our use of a scanning Bragg reflecting crystal interferometer as a fast chopper. Although they have been used with X rays, crystal interferometers work equally well with neutrons4. The interferometer is used as a phase sensitive neutron switch, in which a crystal translation of 0.96 A is sufficient to redirect the beam. At larger translational amplitudes the interferometer has a corresponding multiplex advantage over other neutron choppers. Two of these interferometric neutron choppers could be used to construct a Fourier transform neutron spectrometer with 1,000 times the resolution of competing spectrometers. With a pulsed source a single interferometric chopper could be used to construct a time of flight spectrometer which would provide high resolution even with fast neutrons.

Abstract: The typical dc chopper motor controller consists of two thyristors, two or three diode rectifiers, a commutating capacitor, and one or more commutating inductances The major art in circuit design is selecting the most suitable configuration for the given application, particularly the location of the inductances It is desirable to minimize the inductance in certain loops and to carefully choose the inductance in other loops A computer-aided analysis and optimization technique has been applied to several attractive chopper circuits It appears that inductance in series with the auxiliary thyristor favors turn-off of the main thyristor at the expense of the auxiliary thyristor and vice versa The best arrangement has most of the commutating inductance in a path that is common to both thyristors Where one of the thyristors has a diode connected directly across it, there is generally an optimum value of inductance which yields maximum turn-off time If no such diode is used, the maximum turn-off time is obtained when the inductance is zero

Abstract: A control system of a dc separately excited motor for electric vehicle drive is described. The armature of the motor is controlled by a thyristor chopper, whereas the field is regulated by a highfrequency transistor chopper. The control scheme combines the advantages of both series and shunt motors and permits maximum possible acceleration within the transient thermal ratings of the motor. In addition, motor torque becomes smoother under all operating conditions. A complete drive system has been formulated, designed, and analyzed, and performances have been evaluated on a hybrid computer. At present, the breadboard of the drive system is being tested in the laboratory.

Abstract: A thyristor-controlled chopper circuit is used on the rotor side for speed control of a slip-ring induction motor drive. A small signal dynamic model is developed for this particular drive which can be used for studying closed-loop drive performance. Theoretically obtained results are compared with those obtained experimentally.

Abstract: A control circuit for controlling supply of current for electric motor has a chopper circuit connected with a battery in series. The chopper circuit is constructed with such as power transistors or power thyristors, and the ON-OFF operation thereof is controlled by a driving pulse. A command signal is produced at a movable tap of a potentiometer, across which a D-C control voltage from the battery is applied. In order to determine the duty and the control frequency of the chopper circuit, a duty controlling oscillator circuit is provided, which generates an output signal on the basis of the command signal from the potentiometer. The duty controlling oscillator circuit includes an integrator composed of an operational amplifier having a negative feedback of a condenser, to the -input terminal of which the command signal is applied. Another operational amplifier having a positive feedback of a resistor operates as a hysteresis comparator, to the +input terminal of which is applied the output from the integrator and to the -one of which a divided reference of the D-C control voltage. In response to the output signal from the hysteresis comparator, a driving pulse generator produces a driving pulse to the chopper circuit.

Abstract: An improved battery charger circuit for rapidly charging batteries by increasing the rate of battery charge acceptance through periodic battery discharge pulses during the charging process includes first and second chopper circuits coupled in parallel through an inductor across the DC source for coupling to a battery. The first chopper circuit controls the amplitude of battery charge current while the second chopper circuit controls the amplitude of battery discharge current and provides a low impedance conduction path for discharge current to be returned to the DC source, thus realizing an efficient battery charger circuit.

Abstract: A direct current motor control circuit in which the armature is arranged for reversible connection in a main path for current to flow from a first supply terminal to a second supply terminal through the armature and a current chopper. A pair of switches between which the armature is connected are controllable to effect this reversible connection in the drive mode and to connect the armature across a bridge to permit return current to flow from the second terminal, in either direction through the armature toward the chopper in a regenerative mode, one or more diodes being provided for completing a return path for the return current to flow to the first terminal.

Abstract: A surface potentiometer has a conductive shield housing provided in proximity to a body to be measured, a cage-shaped chopper rotatable within the housing, and an electrode disposed further inwardly of the chopper. The chopper is rotated to induce in the electrode a voltage corresponding to the potential of the body to be measured, thereby measuring the surface potential of the body to be measured.

Abstract: There is disclosed a propulsion and brake effort control apparatus and method operative with the motors of a transit vehicle, including programmed microprocessor control apparatus for comparing the motor current desired by the vehicle control P signal with feedback information from the motor operation to determine the requested motor current by the phase angle relationship of ON and OFF pulses supplied to the current controlling chopper apparatus. The requested current and motor effort can be controlled by the operation of an effort control parameter provided in relation to high and low determined limits of the power supply line voltage, a high determined limit of the line current in relation to the motors and the current request signal.

Abstract: The combined harvester has a chopper in the region of the straw ejection hood after which is fitted a distributor device in the form of several guide plates which form downwards open channels. The plates diverge away from the machine longitudinal axis towards both sides. The guide plates are so arranged that the total cross-section of all channels on the machine side away from the grain to be cut is greater than that of all channels on the machine side facing the grain to be cut.

Abstract: PURPOSE:To detect the light acoustic effect output obtained and the output obtained by photoelectrically converting the fluorescence radiated again from the sample, simultaneously by illuminating the light onto the sample disposed in the sample chamber connected to the base chamber through the gas passage in which the thermal flow detecting element is disposed. CONSTITUTION:The sample chamber 3 of the detector A and the base chamber 4 are connected by the gas passage 5 and at the outlet side of the gas passage, the thermal flow meter type detectingelement 9 is mounted. The sample 2 is placed in the sample chamber 3 and the homogeneous light is illuminated through the light transmission window 6 as an intermittent light of a constant frequency by the light chopper B. The pressure of the gas due to the thermal expansion of the ambient gas by the sample is detected by the detecting element 9 and it is fed to the operation amplifier C as a signal a indicating the acoustic effect output and further operation processed together with the signal indicating the wave length and the strength emitted from the light chopper B and transmitted to the indication amplifier D. The fluorescence reradiated from the sample 2 is detected by the fluorescence detector 11 and the electric output signal is operation processed by the operation amplifier F and fed to the indication recorder D. In this manner, the thermal quality and the optical property due to the light absorption of the sample are simultaneously determined.

Abstract: An improved optical chopper, developed particularly for use in a double beam atomic absorption spectrophotometer, receives light beams from two separate sources and sequentially switches them into two separate paths and instantly thereafter the second light beam enters the first path, followed immediately by the first beam entering the second output path and then the second beam entering the second path; alternatively, the chopper is arranged so that the first light beam enters the first output path followed by the first light beam entering the second output path, and then the second light beam enters the first path and the second light enters the second path; also, during one segment of the choppers cycle, both beams are blocked from both output paths.

Abstract: A method is presented for calculating the value of filter inductance such that while the discontinuous conduction will be eliminated and current ripple will be reduced to the prescribed limits, its (filter inductance) adverse affects, such as deterioration of transient response, etc., will be minimal.

Abstract: The pressure difference across a pneumotach restriction is sampled with a gas chopper connected across a pressure difference detecting transducer. The gas chopper alternates the pressures backward and forward in application to the transducer so that the latter develops an AC sampling signal, the strength of which is related to flow. This AC signal is sampled in synchronism over intervals having a duration related to the power line frequency to develop an integrated value of the pressure difference free of drift caused by power line interference. The resultant signal is smoothed and summed in alternating response at double the gas chopper sampling rate to give a smooth output which is then multiplied by a linearizing circuit to obtain a flow signal which is proportional to the pressure difference. Specific gas flow structures and electronic sampling circuitry are disclosed.

Abstract: This paper describes a positive-feedback situation which arises due to interaction between the constant-power input characteristic and the input-filter impedance characteristic, in a d.c. chopper controller. The limiting condition for convergent oscillation is predicted and confirmed by practical measurements on a 250 A, 400 V chopper.

Abstract: A sulfur monitor analyzer is disclosed and utilizes a burner or flame holder, a burner or reaction chamber, a photomultiplier tube, a light collimator, and chopper blade members with openings so as to permit a flame disposed in the burner or reaction chamber to be seen by the photomultiplier tube at all times. A chemiluminescent radiation mask is disposed operatively between a portion of the chemiluminescent radiation and the photomultiplier tube so as to provide a chopper open mode of operation at which time the photomultiplier tube receives the flame radiation and a fraction of any chemiluminescent radiation surrounding the flames with any remaining fraction of any chemiluminescent radiation being obscured permanently by the chemiluminescent radiation mask. When the chopper is in the closed mode of operation, the photomultiplier tube receives only the radiation from the flame through an aperture defined by an opening in the opaque segment of this chopper or chemiluminescent radiation mask.

Abstract: PURPOSE: To enhance response to the variation of output voltages of a generator by providing a comparator which generates an on-off signal for a chopper depending on the magnitudes of the output of a voltage regulator and the sensed values of field currents. CONSTITUTION: A voltage sensor 63 senses the magnitude of the output voltages of a generator and converts the sensed signal into a proper signal level. The output of a current transformer 51 is converted into a proper signal level by a current sensor 64. The output of the voltage sensor 63 and the output of a preset unit 23 are input to a voltage regulator 61 in order to obtain the output for controlling the conduction rate of a chopper 5 so as to constantly keep the output voltage at a preset value. The output of the voltage regulator 61 and the output of the current sensor 64 are compared by a current comparator 65, whose output is an on-off signal for the chopper 5. In response to this signal, the chopper 5 is driven by a driver 66. In this constitution, stable control can be accomplished without an impact from the distortion in the generator voltages. COPYRIGHT: (C)1980,JPO&Japio

Abstract: A polyphase variable frequency inverter with output voltage control provides a polyphase AC output from a constant potential DC supply, and comprises a chopper circuit and an inverter circuit. The chopper circuit further comprises a silicon controlled rectifier in parallel with a reverse biased diode. The anode of the silicon controlled rectifier and the cathode of the reverse biased diode are connected to the positive terminal of the constant potential DC supply while the cathode of the silicon controlled rectifier and the anode of the reverse biased diode are connected to the respective silicon controlled rectifiers and reverse biased diodes of the inverter circuit. The inverter circuit further comprises a plurality of branches, each including a first silicon controlled rectifier in series with a second silicon controlled rectifier, each such silicon controlled rectifier having in parallel therewith a reverse biased diode. The polyphase AC output is derived from the mid-point junctions of the respective silicon controlled rectifier-reverse biased diode branches of the inverter circuit. It is a feature of a specific embodiment of the present invention that the inverter circuit exhibits a constant RMS polyphase AC output voltage to frequency slope characteristic.

Abstract: There is disclosed a programmed microprocessor control apparatus and method for a transit vehicle electric motor through operation of a chopper apparatus. The microprocessor program controls the motor braking effort in brake mode through operation of the brake resistors and the motor tractive effort in the power mode through the motor field shunt operation.

Abstract: This paper considers a computer-simulated system comprising a nonlinear dc motor pulse fed from a thyristor controller. Simulated steady-state and transient performance from a general circuit simulation program allows the stability of a motor design and characteristics of a controller to be predicted and judged. All chopper circuit semiconductor static and dynamic electrical requirements plus motor losses can be determined for any imposed mechanical load conditions. A current-impulse commutated dc chopper/controlled compound motor simulation is presented and results correlate excellently with those obtained experimentally.