Abstract: A main power supply unit 10 of this power supply apparatus for laser comprises asingle-phase rectifying circuit 16 for receiving a single-phase AC voltage E.sub.A at a commercial frequency to convert (rectify) it into a direct current, a capacitor 18 for temporarily storing the DC power from the single-phase rectifying circuit 16, a charging circuit 20 connected between the single-phase rectifying circuit 16 and the capacitor 18, and a lamp current supply circuit 22 connected between the capacitor 18 and an excitation lamp 102. The charging circuit 20 includes a switching element 24 for charging connected in parallel with the capacitor between the single-phase rectifying circuit 16 and the capacitor 18, an inductance coil 26 connected in series between the single-phase rectifying circuit 16 and the switching element 24 for charging, and a diode 28 connected in series between the switching element 24 for charging and the capacitor 18.

Abstract: A phase control system has a stable timebase phase reference generated by an internal phase reference generator. The control includes a method for estimating and compensating phase distortion when an inductive load is driven by an AC voltage source having significant line impedance. A digital phase comparator estimates a phase error between the timebase phase reference and the voltage source. At the initialization of the phase control system, the phase reference clock period is frozen for a fixed number of cycles to determine an average phase error due to the phase distortion caused by the line impedance. The estimated phase error is then corrected to account for the average phase distortion error.

Abstract: A switching power supply unit controls an output voltage of a power supply without monitoring an output voltage. The switching power supply unit includes a pulse width modulator for generating a control signal to turn on and off a switching transistor. A central processing unit outputs a modulation signal to control the pulse width modulator while sensors detect an input voltage, an output current and a peripheral temperature. A table is used by the central processing unit to store information about a relation between the detected values from the sensors and an ON time of the switching transistor. The central processing unit then selects an ON time of the switching transistor from the table according to values detected by the respective sensors to thereby provide control for switching the switching transistor on and off.

Abstract: A motor drive method and apparatus for reducing noise of a motor. The motor drive apparatus includes first, second and third half bridge circuits. Each of the first, second and third half bridge circuits includes a first transistor which is adapted to form a current path between a first operational potential and an output terminal thereof and a second transistor which is adapted to form a current path between a second operational potential and the output terminal thereof. Each of the output terminals are connected to the corresponding drive coil of a motor. Each of the first and second transistors includes a control terminal to which a control signal is supplied.

Abstract: An electrostatic precipitator circuit has an input terminal supplied DC voltage, an output terminal connected to a precipitating capacitor, a storage capacitor connected between ground potential and the input terminal, and a recovery capacitor whose one electrode is applied with ground potential. The circuit further includes a current path switching unit having a common terminal and first and second switch terminals to be connected to the common terminal, the common terminal being connected to a non-ground electrode of the storage capacitor.

Abstract: An improved method and apparatus for handling the large load currents which occur with overloads, short circuits, and momentary overcurrents such as in starting motors or cold incandescent lamp filaments. The method involves turning the load current off when an overcurrent is detected, and then back on again before the end of the half-cycle in which the overcurrent occurred. This allows more current to flow during the half-cycle without the need to increase the peak current capability of the power-handling components. With an incandescent lamp load, this results in more rapid lamp brightening without the need for larger, more expensive components. Several embodiments are disclosed which respond to different features of the power line voltage cycle, including a very low-cost microprocessor circuit and power supply.

Abstract: A power supplying system is adapted to a subscriber terminating equipment that supplies power to a subscriber terminal equipment based on a supply of power from an external power supply part. The power supplying system includes an excess current limiting circuit stopping a supply of power within the subscriber terminating equipment when an excess current is generated in the supply of power from the external power supplying part, and an excess current detection circuit detecting an excess current state.

Abstract: An apparatus and method for controlling the voltage applied to an induction motor is taught. Load sensing is incorporated by monitoring the current through the motor, and combining that signal with a signal derived from the AC line voltage and AC voltage across the motor. This composite signal is averaged, with the resulting averaged signal being utilized to control a device for modulating voltage applied to the motor such as a phase control integrated circuit device.

Abstract: An apparatus and method for controlling the voltage applied to a load is taught. The method includes receiving an AC line voltage, generating an operating AC voltage from the AC line voltage and applying this operating AC voltage across the load. A measured signal which is a function of the magnitude of the operating AC voltage is generated, and then averaged to generate an average signal representative of the average value of the measured signal. The operating AC voltage is continually readjusted in response to changes in the average signal. The apparatus implementing this method includes terminal means for receiving an AC line voltage, means for generating an operating AC voltage from the AC line voltage, connector means for applying the operating AC voltage across the load, and voltage detection means for generating a measured signal which is a function of the magnitude of said operating AC voltage.

Abstract: An improved phase-controlled power control apparatus includes a semiconductor switching element for varying the effective power delivered to a load from the power lines. The conduction angle of the semiconductor power switch element is varied from a nominal angle to compensate for changes in power line voltage and for changes in load current. The amount of load current flow is continuously compared to the power line voltage to detect any overcurrent condition, even very close to the zero-crossing of the power line voltage. The shape of the transition from load current on to load current off (or vice versa) in controlled to minimize audible noise from the load. The load current can be shared between a plurality of compatible power control sections.

Abstract: A phase-controlled power modulation system switches modes in response to circuit-threatening conditions to avert the necessity of a shutdown. Normal operation is in reverse phase control (RPC) mode. When an inductive load sensor detects the presence an inductive load, the system switches to a forward phase control (FPC) mode (FPC) to minimize voltage spikes that would otherwise result from the load's opposition to voltage transitions. When an overcurrent sensor detects an overcurrent, the system switches into an asymmetric hybrid mode (AHPC) to maximize delivered power while remaining within switch current handling capacity. In AHPC mode, an RPC component of a half-cycle waveform is cut off at the current limit, while an FPC component of the same half-cycle waveform is triggered after the source voltage drops to a confidence threshold below the current limit to ensure that current limiting is not triggered again during the same half-cycle.

Abstract: A microwave oven having a fan motor rotation control function comprising an absolute humidity sensor for sensing the humidity inside the microwave oven, a fan motor for discharging water vapor inside the microwave oven externally, a microprocessor and a keyboard. The improved microwave oven further comprises a phototriac connected between said fan motor and a supplying line of AC power source for controlling AC power supplied to the fan motor in accordance with a plurality of control signals from the microprocessor and a zero crossing signal generating circuit for detecting a zero point from AC power voltage during a constant cycle to generate a predetermined width of pulse signal at the zero point and for applying the predetermined width of pulse signal the microprocessor.

Abstract: A remotely controllable, full scale, AC or DC power attenuator, for attenuating power to a load as a function of an input control signal which represents a selected percentage of power to be applied to the load. Bidirectional series switch means are responsive to the input control signal for connecting and disconnecting power to the load.

Abstract: A controller can control controlling a precipitator. The controller has a power modulator. The modulator has a control terminal and is coupled to the precipitator. The power modulator is adapted to be powered by an alternating current. The modulator can operate to regulate the drive to the precipitator in response to a control signal on the control terminal. The controller also has a measurement means coupled to the precipitator for providing a plurality of measurement signals corresponding to a plurality of operating parameters of the precipitator. Also included is a processing means having a program. The processing means is coupled to the measurement means and the power modulator for producing the control signal and for regulating the power modulator in response to the measurement signals.

Abstract: Structure for and method of controlling the firing point of thyristors in a phase controlled contactor in a resistance welding circuit in accordance with variations in current line voltage and/or one of resistance and inductive impedance in the welding circuit including structure for and the method of determining the firing point in a cycle of alternating electrical energy fed to the welder in terms of its distance from zero voltage cross over point and determining the current lag after a subsequent zero voltage cross over point of the voltage signal, determining the power factor of the welding circuit from these angular measurements and selecting a new firing delay for the contactor in accordance with the circuit power factor and the percent heat selected in the welding circuit, and subsequently correcting the firing delay in accordance with the percent heat selected in view of changes in the line voltage and circuit current.

Abstract: A circuit for regulating the output of a DC power supply that substantially eliminates turn-on transients induced by the switching of a silicon-controlled rectifier (SCR). A zero-crossover detector senses the AC voltage waveform of an applied power source and provides a trigger signal at the zero-crossing point. The trigger signal is applied to cause induction of the SCR's and raise the output voltage when the power supply output drops below a regulated value, and is interrupted so as to inhibit conduction of the SCR's and decrease the output voltage when the power supply output exceeds the regulated value.

Abstract: An electronic switching device having a detection circuit or input circuit powered by an external source and load is described. The external source and load are in a series circuit with a power switching element which thereby provides switch controlled power in response to an output signal generated from a detection circuit. A current limiting device is connected in series with the power switching element, and an excess current detection circuit responds to excessive current flowing in the aforemention series circuit to interrupt the power switching element when an abnormally large current is passed. Circuitry is provided for holding the current limiting device in its operable or current interrupting state for a predetermined period of time.

Abstract: A method and apparatus to maintain the current-conducting state of a gate-turn-off thyristor by appropriate triggering. To maintain the thyristor's current-conducting state reliably and with little ignition energy consumed, a comparator signal is generated as soon as the voltage drop across the thyristor exceeds a preset limit value by a comparator stage. The comparator signal has a preset duration defined by a pulse duration limiting stage, and, if necessary, a subsequent pulse magnitude limiting stage can change the pulse magnitude as a function of the interval between two subsequent ignition current pulses. A controllable current source connected to the thyristor gate is controlled by these magnitude and duration limited pulses, but this controlled current source only triggers the thyristor when the limit value is exceeded.

Abstract: An induction heating apparatus includes an inverter (5) which is driven by a DC power supply (3), and the inverter (5) includes a heating coil (9) and a switching transistor (11) which is connected thereto in series. The switching transistor (11) is turned on or off by a control circuit (35) to control a current flowing through the heating coil (9). The control circuit (35) takes a collector voltage of this switching transistor (11) from the point where the heating coil (9) and the switching transistor (11) are connected in series through a terminal (39). An integrated voltage of this collector voltage is generated in the control circuit (35), and the collector voltage is compared with the integrated voltage. When the former becomes lower than the latter, after a certain delay time, a switching signal is outputted from the control circuit (35), and the switching transistor (11) is turned on. Such a delay time is preferably varied in response to the magnitude of the collector voltage.

Abstract: A power control circuit in which a direct current voltage (Vp) proportional to the a.c. power applied to a load (L) is derived from voltages (Vc and Vv) proportional to the a.c. current flowing in the load (L) and the a.c. voltage across the load, respectively, and compared with a voltage (Vnp) representing nominal power to the load to provide a d.c. signal (Vd) the amplitude of which is utilized in conjunction with a staircase or ramp generator (SG) to add or deduct cycles of the a.c. power to or from the load circuit according to a predetermined load power rating and in dependence upon variations in the a.c. supply voltage to the load and changes in resistance of the load.

Abstract: The invention relates to a circuit arrangement for controlling the temperature of an electric heating element (10), where the resistance of the element is utilized as a measure of the temperature. When the element is switched on, the current flowing through the element is scanned by a small measuring resistor (16). The voltage drop (U.sub.1) arising over this resistor is compared to a reference value (U.sub.2) for interrupting the effect supply to the element when the element has achieved the desired temperature. Thereafter a weak test current is fed through the element, and a voltage drop (U.sub.3) dependant on the element temperature is compared to an additional reference value (U.sub.4) for again connecting the effect feed when the element temperature has dropped to a predetermined level. By means of the invention, which can be used for the temperature control of, for example, electrically heated car seats, both continuous temperature control and adjustable on/off-hysteresis are obtained.

Abstract: The power drawn by a load (R.sub.L) from an A.C. network is controlled by an operational amplifier (OP1) and a power transistor (TR2). The operational amplifier makes the transistor leading when the voltage of its inverting input which is derived from said network, is lower than a reference voltage supplied to its non-inverting input. The pulses through the load take a form corresponding to the first and last parts of a sinusoidal half-wave. Their time lengths are shortened according as the voltage of the feeding network increases, and vice versa. FIG. 1.

Abstract: A control device for an electrostatic dust separator (10,11) intended to control in relation to the recorded level of direct current (104) and direct current voltage (102) in the dust separator and with the help of the supply voltage (6a) passes through the zero point the switching in and/or out of the rectifiers (8, 8a) wired into the power supply lead (6a) to the dust separator, usually in the form of two thryistors. The recorded value for the current (104) and the recorded value for the voltage (102) together with the information in respect of the passage through zero of the supply voltage (100) are connected directly via conversion circuits (25, 26) to a data processing unit (112).

Abstract: A phase control circuit, for energizing lower voltage loads and the like from a higher voltage A.C. source, utilizes power switching means in series with the load across the source. The load voltage and current are sampled and compared to reference values to determine if the load resistance is less than or greater than a desired value and the output voltage of an integrator is adjusted accordingly. The integrator output voltage establishes the time, after each source waveform zero crossing, at which the power switching device enables load current flow. A reset circuit prevents the power switching device from conducting in the event that a line zero crossing is not properly detected, to preclude damage to the switching device and/or load overvoltage. A circuit is also provided for gradually increasing load current at start-up to limit inrush currents to the load.

Abstract: A method for detecting breakdowns in an electrostatic filter in which single measured values of equal phase of successive half waves of the filter voltage and crest values of successive half waves of the primary current are compared with one another and in which the differences of the measured values at which a breakdown signal is delivered are made dependent on the existing filter voltage or the primary current.

Abstract: A trigger control circuit is provided for producing firing pulses for the thyristor of thyristor control system such as a power factor controller. The control circuit overcomes thyristor triggering problems involved with the current lag associated with controlling inductive loads and utilizes a phase difference signal, already present in the power factor controller, in deriving a signal for inhibiting generation of a firing pulse until no load current is flowing from the preceding half cycle and thereby ensuring that the thyristor is triggered on during each half cycle.

Abstract: A system for monitoring heater elements of electric furnaces so as to identify individual failures, such system comprising an arrangement for detecting the electrical open state of any one of the heater elements, including a current transformer for monitoring current flow; and the capability of monitoring element voltage, such that no element current in the presence of a minimum element voltage is defined as, or taken to be, a failure; further including the provision of a master alarm indication of a defined failure in any of the elements and also an individual alarm indication to indicate which element has failed.

Abstract: A method for operating an electrostatic precipitator with a DC voltage and superimposed pulses or superimposed AC voltage in which individual parameters such as amplitudes, pulse repetition frequency, pulse width, etc. are iteratively and continuously varied in such a manner that the sum of the pulse and the DC voltage power approaches a minimum. A computer which calculates, from the dust load and the absorbed electric energies of the filter, control commands for the DC and pulse voltage source is used for this purpose.

Abstract: The present invention relates to power supplies, and more particularly, to a power supply which is particularly suitable for controlling a high intensity discharge (HID) lamp. In particular, the present invention relates to an HID lamp power supply which provides fast warm up for a cold lamp, regulation against line voltage fluctuations and a lamp starting circuit which provides extremely fast restart when the lamp is hot and has been turned off momentarily.

Abstract: The automatic recording of the current-voltage characteristic of an electrostatic filter in which the characteristic obtained upon stepwise variation of the control is displayed to the operating personnel and at the same time saturation phenomena and voltage maxima are picked up.

Abstract: A control apparatus for a cycloconverter includes m sets of bridge converters connected between the input terminals of an m-phase load (m.gtoreq.3) and is applied for a cycloconverter of which the common connection point of the bridge converters is disconnected from a neutral point of the load. The output voltage of each bridge converter is controlled by a reference voltage signal during a 1/m period of one cycle of the load voltage. The center of the 1/m period is located at a positive or negative maximum amplitude point of the load voltage. The output voltage is also controlled during the remaining period of (1-1/m) by a phase control input signal corresponding to a difference between a reference current signal and the load current. The reference voltage signal and the phase control input signal are selected by switching signals from a logic circuit for detecting phase voltages of the load to alternately be applied to the phase control circuits.

Abstract: A regulated constant current is supplied to a welding load by an SCR power supply having an SCR rectifier network interposed in series between the welding load and applied input power with the SCR power supply comprising means for generating a first feedback signal proportional to arc current which substantially coincides in time and phase with the arc current; means for generating a second feedback signal proportional to arc current which is substantially nonresponsive to the arc current fundamental ripple frequency, means for weighing the first and second feedback signals in a predetermined proportion to establish an error feedback control signal and means for applying trigger signals to the SCR rectifier network in timed synchronism with the input AC power line as a function of the error feedback control signal.

Abstract: A regulated power supply circuit includes a transformer having a primary winding and a secondary winding electromagnetically coupled by an iron core. A source of AC operating voltage is coupled to the primary winding of the transformer via an actuable switch means. A load circuit coupled to the secondary winding circuit is adapted to be energized by a voltage developed in the secondary winding circuit. Means are provided for sensing the polarity of each half cycle of said source of AC operating voltage. Memory means are coupled to the transformer for providing information representative of the polarity of each half cycle of the source of operating voltage applied to the primary winding of the transformer. The memory means are operable to maintain the information for a period of time when the switch is actuated to be opened. Means are also provided for sensing a parameter in the secondary winding circuit related to the energy available in the secondary winding circuit.

Abstract: There is provided a precipitator system including a voltage controller which produces from an alternating power source a variable output. This variable output drives a high voltage converter which applies a high voltage to a precipitator. This variable output is controlled by a control signal from a command subsystem. Preferably, the command subsystem is operative to repress the drive to the high voltage converter in response to its loading exceeding a predetermined limit during a corresponding limit interval. After this limit interval, the command subsystem is operative to rapidly restore productive drive to the high voltage converter, preferably by the next half cycle of the power source that has a polarity opposite to that existing at the beginning of the limit interval. In this fashion stablized operation is quickly achieved. Also included, preferably, is a conductive element that is coupled to the high voltage converter.

Abstract: In a method and system of controlling the effective value of alternating current supplied to a load through controlled semiconductor switching elements which are connected in parallel opposition, circuits are provided to produce data ##EQU1## where .DELTA.I represents an increment of the load current, .DELTA..alpha. an increment of the ignition angle .alpha. and I.sub.90 the effective value of the load current at an ignition angle of 90.degree.. .DELTA..alpha. is calculated according to an equation ##EQU2## where K is a constant smaller than 1. Then .DELTA..alpha. is added to an ignition angle .alpha..sub.1 in a preceding half cycle to determine a new ignition angle which is used to control the controlled semiconductor switching elements.

Abstract: A two-terminal overcurrent sensing transistor circuit of the fold-back type is inserted in electrical series relationship with an AC load and an associated load-energizing, solid state, semiconductor switch. Under normal operating conditions, the transistor circuit presents a very low impedance to permit load energization when the solid state switch is conducting, and hence has a very low impedance. Upon sensing an overcurrent condition, caused for example by a short circuit across the load, the transistor circuit rapidly switches to and locks into a high impedance circuit protection state to limit current through the series-associated solid state switch. A charged capacitor holds the transistor circuit into its high impedance state subsequent to clearing of the short circuit fault until reset by interrupting the application of power to it. The disclosed protection scheme finds particularly advantageous use in the short circuit protection of AC line-operated proximity switches.