Abstract: An aquarium heater override control system for use with an aquarium heater in which the system includes a temperature probe placed in the aquarium environment and a control module with temperature settings, visual indications of power presence, circuit testing and reset buttons connected thereto that provides power to the heater so long as the temperature within the aquarium does not exceed a predetermined threshold value of the override control system.

Abstract: A proximity switch circuit including first and second transistors Q4, Q6 connected as a long tail pair with an inductive sensing circuit LC connected to one leg thereof and an emitter follower circuit Q7, Q8 connected between said one leg and the base of the transistor of the other leg, whereby an oscillator circuit can be provided which is non-critically damped to enable faster speed of operation of the proximity switch.

Abstract: A dry type transformer has an iron core, high voltage windings embedded in cast resin, and low voltage windings resin encapsulated. The low voltage winding is constructed with flexible sheet conductors coincident with layer insulation sheets that extend beyond the edge of the sheet conductor. Cooling air ducts are fabricated in the low voltage windings as it is wound. To prevent the extension of the layer insulation sheets from collapsing over the formed air ducts during a vacuum and pressure resin impregnation process, reinforcing means are added to the extensions to prevent them from collapsing.

Abstract: The present invention provides an integrator 5 with switched hysteresis for inductive proximity switches comprising a reference current source IREF connected between a reference voltage supply rail and a first side of a current mirror, a second side of the current mirror being connected to a proximity switch rectifier, the first side of the current mirror being connected to a capacitor CINT and to one input of a two input comparator, the other input of the comparator being held at a threshold level, wherein a fixed hysteresis current source IHYST is provided in parallel with the current reference source IREF, the fixed hysteresis current source IHYST producing a switchable current which is a fixed proportion of the current of the current reference source IREF, the fixed hysteresis current source IHYST being switched on (off) when a target is detected and off (on) when no target is detected. This invention provides for reduction of effects detrimental to the speed of operation of the switch.

Abstract: An uninterruptible power supply for supplying a load with AC output power generates the AC output power from an AC input source when the AC input source is within settable voltage limits and transfers to generating the AC output power from an auxiliary source of DC power when the AC input source is outside the voltage limits. A microprocessor provides monitoring and sampling of the AC input voltage to determine its amplitude and frequency, and uses this information to set the magnitude and frequency of the AC output voltage by generating a sine reference signal to control the AC output frequency and voltage phase angle. The microprocessor maintains a voltage phase relationship between the AC input power and AC output power to eliminate voltage and current transients at transfer times between the AC and DC input sources that would be present if the AC output suddenly had a drastic, voltage phase angle change.

Abstract: A closed loop pulse width modulator (PWM) inverter corrects for variations and distortion in the output AC voltage waveform caused by non-linearities of the switching devices or changes in the DC link voltage. A signal is generated that is a volt-seconds representation of the voltage error between a voltage command and the actual AC output voltage of the PWM inverter. The volt-seconds error signal becomes a controlling means in the closed loop of the PWM inverter to regulate the output AC voltage of the PWM inverter. Another signal that represents changes in the DC link voltage also modifies the voltage command signal. The system will compensate for the non-linear behavior of the PWM inverter due to deadtime, minimum on-times and off-times, and DC link voltage variations and voltage drops across the switching devices, and will also allow the operation of the inverter in a linear fashion for the region of operation when one or more of its phases are saturated, i.e., either full on or full off.

Abstract: A method and apparatus provides for a measurement technique which approximates the true rms value of a current waveform. The technique involves converting the current waveform to a voltage by rectification and determining the peak value and the average value of the resultant voltage. A summing circuit combines the two values at a predetermined ratio to create a DC voltage that is approximately equal to the rms value of the input currents. The DC voltage output is suitable for a wide range of applications. A combination of the approximation circuit with a time integrating circuit and a level detecting circuit produces a low cost solid state overload relay in a preferred embodiment of the invention. Other uses include metering and use as a current feedback control signal for controlling PWM inverters and the like.

Abstract: A weld controller utilizing a constant current control employs a stepper program for increasing current boost in predetermined percentage increments or steps following a predetermined stepper current profile to provide compensation for contact tip wear. The weld controller acquires weld power data in the form of current and voltage samples for each step of the stepper program, and computes Volt Amperes or power from this data during an acquisition run through the stepper program. The stepper program specifies a constant current at each step. Associated with each incremental current step, weld power that is required to produce that weld current is determined by the weld controller to generate a characteristic power curve. The power curve will be over the range of currents as specified by the combination of the programmed weld current and the range of current boost as specified by the stepper schedule. The weld controller will build a table of values relating weld current and delivered power or Volt Amperes.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance for the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence to verify that components in the measurement circuitry are within specified tolerances.

Abstract: A weld controller utilizes a neural network to compute power factor of a secondary circuit of a welding transformer supply power to a workpiece through a pair of welding electrodes. Phase controlled switches supply power to the transformer and the neural network uses the phase angle at the time of energization of the switches and the length of time that the switches conduct to compute the power factor. The computed power factor is compared with previous computations of power factor online and any changes are interpreted as changes in resistance of the secondary circuit. This provides a measure of contact wear and the weld controller can compensate for these changes by increasing weld power. The neural network is adaptable for use with other types of control systems.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance of the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The hazard current is displayed and if it exceeds a predetermined threshold, the LIM will provide audio and visual alarms. A serial communications channel allows the LIM to communicate with other intelligent devices. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence. Line frequency is also determined by the LIM.

Abstract: A line isolation monitor (LIM) indicates the maximum hazard current of an ungrounded polyphase power distribution system. The LIM is microcontroller based and continuously monitors a fault impedance for each phase of the distribution system. The fault impedance is determined by the LIM by injecting a continuous sine wave measurement current into a ground terminal to generate a measurement voltage across the fault impedance. Using the measurement voltage and current, the LIM calculates the fault impedance and, using this impedance, calculates the hazard current based on the maximum line to ground voltage of the ungrounded system. The LIM has means for self-calibration and self-testing while on-line and during a power-up sequence. These tests compare measured and theoretical values of circuit parameters of voltage and current sensing circuits.

Abstract: A pulse width modulation DC to DC converter operates in an open loop mode to convert the DC output of the AC to DC converter to a desired, predetermined DC level using pulse width modulation techniques and a switching configuration substantially similar to that of the AC to DC converter.

Abstract: A dry type transformer has an iron core, high voltage windings embedded in cast resin, and low voltage windings resin encapsulated. The low voltage winding is constructed with flexible sheet conductors. Insulating material includes an apparatus to secure the windings in place during a vacuum and pressure resin impregnation process. The result is a coil that exhibits high short circuit protection due to the tightly bond conductors comparable to completely resin encased molded transformers at a substantially reduced cost.

Abstract: A weld controller employs a stepper program for increasing heat boost in one percent increments or steps to provide compensation for contact tip wear. The weld controller acquires weld current data in the form of current samples for each step to create a characteristic curve or nominal current profile for the stepper program. Subsequent operations of the weld control utilize high and low current limit thresholds that track the nominal current profile. The thresholds can be defined as a fixed offset from the profile or as a percentage of the profile at each step of the stepper program. This allows the use of current limits to be established in close proximity to the nominal weld current at all times, enabling the use of tighter tolerances.

Abstract: A dry type transformer has an iron core, high voltage windings embedded in cast resin, and low voltage windings resin encapsulated. The iron core is manufactured with stacked core steel. After the core is stacked, instead of using banding straps, a heat shrinkable material is wrapped around the core legs and is heated to enable the shrunken material to apply uniform compression over the core legs. This will facilitate coil loading, reduces audible core noise and reduce core losses. In place of shrink wrappable material, a film material with elastic properties could be used.

Abstract: A current mode control apparatus generates an AC power output from a DC input source. The apparatus includes a pulse width modulator (PWM) to produce gate drive signals for driving a power output section having an output inductor and connected across the DC input source. An inner current error control loop coupled between the AC power output and the PWM, controls the average current in the output inductor by generating a current error signal for inputting to the PWM for conversion to the gate drive signals. The current error signal is the difference between the average current and a voltage controlled input signal. An outer voltage error control loop coupled between the AC power output and the inner current error control loop generates a voltage error signal based on the difference between the AC power output and a reference AC voltage.

Abstract: A power output driver circuit that converts a DC voltage into an AC voltage includes a gate driver circuit for turning on electronic switching devices. The gate driver circuit allows for a rapid turn-off of the conducting electronic switching device by having a first conduction path for the gate drive signals that turn-on the switching devices and a second conduction path that rapidly discharges stored energy in the gate/drain capacitance of the switching devices, resulting in a faster turn-off time. A transistor in the gate circuit shunts the stored charge directly to the source terminal of the switching device.

Abstract: An enclosure for electrical or electronic devices having components requiring periodic adjustment is provided with an access opening to the adjustments for the components including a hinged, attachable door for closing and sealing the access opening.

Abstract: A semiconductor package houses a plurality of single two terminal semiconductor components. The package is a plastic or ceramic small outline integrated circuit package and is adapted for surface mounting. Each semiconductor element is in a die form and one terminal is directly bonded to one of the external leads. The other terminal is bonded to a jumper that in turn is bonded to the other lead. The resultant package is encapsulated and the external leads are formed for surface mounting. V-shaped grooves formed on the top and bottom of the package separate each semiconductor component and provide a means to separate each or a combination of individual semiconductor components from the package by allowing them to be snapped apart at the V-groove. The resultant package has a very low profile that allows it to be used in thin profile, high density electronic assemblies.