Abstract: A desaturation detector receives signals from a gate driver and circuitry that indicate whether a power semiconductor device is on and in desaturation. A logic circuit produces a signal as a function of the signals, from which a latch circuit produces an output signal. The signal has first and second values respectively in an as-designed condition, and in a short-circuit condition in which the power semiconductor device is on and in desaturation. The output signal has the first value, and transitioned and latched to the second value in response to a transition to the short-circuit condition, which causes the gate driver to switch the power semiconductor device off. And filter(s) reduce noise within the desaturation detector.

Abstract: A desaturation detector receives signals from a gate driver and circuitry that indicate whether a power semiconductor device is on and in desaturation. A logic circuit produces a signal as a function of the signals, from which a latch circuit produces an output signal. The signal has first and second values respectively in an as-designed condition, and in a short-circuit condition in which the power semiconductor device is on and in desaturation. The output signal has the first value, and transitioned and latched to the second value in response to a transition to the short-circuit condition, which causes the gate driver to switch the power semiconductor device off. And filter(s) reduce noise within the desaturation detector.

Abstract: A device comprises a first magnetically conductive structure, a second magnetically conductive structure, and a circuit coupled the first and second magnetically conductive structures. The circuit senses information pertaining to a permeability of the first magnetically conductive structure relative to a permeability of the second magnetically conductive structure. The device may be used for various flux sensing and control applications, such as in current sensors.

Abstract: A device comprises a first magnetically conductive structure, a second magnetically conductive structure, and a circuit coupled the first and second magnetically conductive structures. The circuit senses information pertaining to a permeability of the first magnetically conductive structure relative to a permeability of the second magnetically conductive structure. The device may be used for various flux sensing and control applications, such as in current sensors.

Abstract: A device comprises a first magnetically conductive structure, a second magnetically conductive structure, and a circuit coupled the first and second magnetically conductive structures. The circuit senses information pertaining to a permeability of the first magnetically conductive structure relative to a permeability of the second magnetically conductive structure. The device may be used for various flux sensing and control applications, such as in current sensors.

Abstract: A device comprises a first magnetically conductive structure, a second magnetically conductive structure, and a circuit coupled the first and second magnetically conductive structures. The circuit senses information pertaining to a permeability of the first magnetically conductive structure relative to a permeability of the second magnetically conductive structure. The device may be used for various flux sensing and control applications, such as in current sensors.

Abstract: A sensor comprises a magnetic flux divider and a winding. The magnetic flux divider comprises first and second magnetic paths through which magnetic flux flows. The magnetic flux divider divides the magnetic flux between the first and second magnetic paths as a function of a total amount of magnetic flux flowing through the magnetic flux divider. The winding produces a signal that is indicative of the total amount of magnetic flux flowing through the flux divider based on the operation of the flux divider. A method of sensing a parameter comprises providing a material with a permeability that varies in accordance with an amount of magnetic flux passing through the material; and acquiring information indicative of the permeability of the material, the permeability of the material being indicative of the parameter. The sensor and method can be utilized to acquire information pertinent to another parameter of ultimate interest, such as information pertaining to a current flow in an electrical circuit.

Abstract: In a method of measuring a current, the current is received at a winding and permitted to flow through the winding, which is wound about a core. The flow of the current through the winding induces a first magnetic flux that flows through the core and that tends to drive the core into saturation. The core is actively reset to prevent the core from being saturated at least during selected time intervals. The current is then measured during at least a plurality of the selected time intervals. In a particularly preferred embodiment, the winding is a primary winding and the resetting step includes applying a reset voltage to a secondary winding using a source that is coupled to the secondary winding. The reset voltage determines a rate at which a net magnetic flux that flows in the core changes in a direction away from saturation. Advantageously, the current sensing method has a tremendous dynamic range.

Abstract: A method and apparatus is disclosed for three phase sensing of a polyphase distribution system to provide true RMS signal monitoring capabilities. Each current transformer is provided with a rectifier and a separate burden to not only provide accurate signal representation of the true RMS currents in each phase, but also provide a DC voltage supply to thereby self-power the circuit. Two configurations are disclosed, one in which two CTs sense all three phases. In this configuration, two phases of the three phase system are used as a single primary winding in each current transformer such that each current transformer produces a voltage representation of a sum of two phase currents. A second configuration discloses the use of a current transformer for each phase. In both embodiments, by providing a separate burden and rectifier for each CT, true RMS signal characteristics can be extracted from the produced discrete signals, while at the same time providing a DC voltage supply for self-powering the circuit.

Abstract: A method and apparatus is disclosed for complete three-phase sensing using two current transformers. Two phases of a three-phase system are used as the primary windings in each current transformer such that each current transformer produces a phasor representation of a sum of the two phases. A three phase sensor is provided to add the phasor representations produced by each of the current transformers and to produce a third phasor representation from the summation. The three phasor representations can then be applied to any conventional overload relay control to monitor each phase and produces a trip signal to open the three-phase system when a phasor representation exceeds some predetermined value, or the magnitudes of the phasors differ by more than a predefined value.

Abstract: An electromagnetic switch for opening and closing a set of contacts has a microprocessor which monitors coil current to determine the state of the contacts. The switch relies on the phenomenon that the inductance of the switch coil changes significantly between the open position of the contacts when the switch armature carrying the moveable contact is spaced by an air gap from the core of the electromagnet, and the closed position in which the armature abuts the core. For an AC energized coil, which is self-limiting in that the increase in inductance from closing of the contacts reduces the current to the holding value automatically, a coil current of less than about one/half of the nominal open contact value is an indication that the contacts are closed.

Abstract: A motor starter for an electrical circuit includes separable contacts for switching an electrical current flowing between a power source and a motor; an operating mechanism responsive to a trip signal for opening and closing the separable contacts; a separable contact state detection circuit providing an operating signal having two states corresponding to the open and closed positions of the separable contacts; a current transformer sensing the electrical current flowing between the power source and the motor and providing a sensed current value; and an overload relay generating the trip signal as an I.sup.2 t function of the sensed current value and the two states of the operating signal. The overload relay employs a pair of thermal time constants which closely model the motor under both natural convection and forced air cooling conditions.

Abstract: A power supply for converting a plurality of alternating current (AC) and direct current (DC) input line voltages to a DC output voltage includes a converter for converting the input voltages to an intermediate voltage at a first node; a switching regulator having a power voltage at a second node for providing a reference voltage therefrom, and for providing a switching signal at a third node from the reference voltage and a feedback voltage; a circuit for electrically interconnecting the first node to the second node whenever the intermediate voltage exceeds a predetermined voltage; a transformer including a primary winding electrically interconnected with the first node, and a secondary winding having a secondary voltage; a feedback circuit cooperating with the transformer for providing the feedback voltage therefrom; a switching circuit responsive to the switching signal at the third node for switching an electrical current from the first node through the primary winding; and a circuit electrically interco

Abstract: A circuit for inputting an ac signal to a digital processor includes a capacitor connected to the input and ground. A rectifier, preferably a transient voltage suppression device, permits the capacitor and also the stray capacitance which couples false signals to the input lead, to charge to one polarity only. A shunt resistor discharges the capacitor on half cycles of opposite polarity, but there is no discharge path for the stray capacitance which therefore charges up to block steady state false ac signals. Series resistors between the rectifier and the input determine, together with the shunt resistor, the minimum input signal level and increase the over surface breakdown voltage to protect the input from transient voltage conditions. A resistor connected between the series resistors and the rectifier, and to ground determines the charging rate of the stray capacitance. The TVS device provides high transient voltage withstand and breaks down without damage in the event of large transients.