Abstract: An arc fault detector for detecting an arc fault in electric power lines includes a two stage arc sensor. The first stage is a current transformer designed for high sensitivity to arc faults but which may saturate and lose detection capability during arc currents at 75A and higher. The second arc fault sensor, which does not saturate, stage senses the voltage across the impedance of the primary of the current transformer, or senses the voltage across the resistance of a section of the load carrying bus which forms the connection through the detector device, or of both, during an arc fault.

Abstract: An arc fault detector for detecting electric power lines includes a sensor for sensing the derivative of the current on the electric power line, a converter circuit for converting the derivative of the line current into first and second signals, the first signal responsive to positive step transitions of arc fault current, and the second signal responsive to negative step transitions of arc current, and a temporal detector for signaling the presence of an arc fault when one of the first and second signals follows the other within a predetermined time, or window, and in which a sequence of one of the signals following the other signal occurs in a second predetermined interval of time.

Abstract: A combined ground fault and arc fault detector includes interrupting contacts which are opened when either an arc fault or a ground fault is detected. The detector includes a test circuit which creates a simulated fault and momentarily de-energizes the coil to test the detector and re-energizes the coil before the interrupting contacts open.

Abstract: An arc fault detecting circuit using a pulse width modulation, or PWM, technique is used to sense series or parallel arc faults. When arc faults occur, typically an arc step in current is followed by broad band arc noise which is caused by the random fluctuations in arc column resistance. In this invention, a logic signal is created which has a duration or width that corresponds to the time interval during which the broad band arc noise generated by the arc is present. Typically an arc fault randomly starts, generates broad band arc noise, and then extinguishes as the next current zero cross of the AC load current is approached. The random start causes PWM of the logic pulse whenever the start of the arc randomly moves with respect to the current zero cross. An arc fault that randomly starts, and then randomly stops, will also cause PWM with respect to the zero cross.

Abstract: Briefly stated, and in accordance with a presently preferred embodiment of the invention, an arc fault detecting circuit using, a pulse width modulation, or PWM, technique is used to sense series or parallel arc faults. When arc faults occur, typically an arc step in current is followed by broad band arc noise which is caused by the random fluctuations in arc column resistance. In this invention, a logic signal is created which has a duration or width that corresponds to the time interval during which the broad band arc noise generated by the arc is present. Typically an arc fault randomly starts, generates broad band arc noise, and then extinguishes as the next current zero cross of the AC load current is approached. The random start causes PWM of the logic pulse whenever the start of the arc randomly moves with respect to the current zero cross. An arc fault that randomly starts, and then randomly stops, will also cause PWM with respect to the zero cross.

Abstract: Briefly stated, and in accordance with a presently preferred embodiment of the invention, an arc fault detecting circuit using a pulse width modulation, or PWM, technique is used to sense series or parallel arc faults. When arc faults occur, typically an arc step in current is followed by broad band arc noise which is caused by the random fluctuations in arc column resistance. In this invention, a logic signal is created which has a duration or width that corresponds to the time interval during which the broad band arc noise generated by the arc is present. Typically an arc fault randomly starts, generates broad band arc noise, and then extinguishes as the next current zero cross of the AC load current is approached. The random start causes PWM of the logic pulse whenever the start of the arc randomly moves with respect to the current zero cross. An arc fault that randomly starts, and then randomly stops, will also cause PWM with respect to the zero cross.

Abstract: An arc fault causes the line voltage across the line terminals of an arc fault circuit interrupter (AFCI) to change its characteristic voltage pulse shape as the line voltage is momentarily removed from the AFCI terminals after the arc extinguishes and before it re-strikes by introducing a flat voltage portion to the pulse shape. This flat voltage portion changes the voltage pulse width. An arc detector/processor detects this change in pulse width to produce a signal indicative of upstream (line side) arcing. The flat voltage portion can also be detected using clamping diodes and charging capacitors.

Abstract: A circuit protection device connected between two lines of an AC power source self checks for an introduced simulated ground fault every half cycle during a period when a trip SCR cannot conduct. If the self check fails, the device is tripped on the next half cycle of different phase. Possible responses to the self check failure include lighting an indicator lamp and locking out the device reset mechanism.

Abstract: An arc fault circuit interrupter (AFCI) detects arc faults by identifying the various signature patterns of arc fault noise while rejecting arc mimicking noise from normal load phenomena.

Abstract: A combined ground fault and arc fault circuit interrupter includes a differential current transformer, a hot electrical line and a neutral electrical line passing through the current transformer and forming the primary thereof, an asymmetrical current transformer having a core through which the hot and common electrical leads pass, and a secondary wound on the core for producing a signal more strongly responsive to the current in the common line than in the hot line. An arc fault detector is connected to the secondary of the second transformer, while a ground fault detector is connected to the secondary of the first transformer, and the outputs of the ground fault and arc fault detectors are both connected to a circuit interrupter arranged for disconnecting the circuit when either a ground fault or an arc fault is detected.

Abstract: Arcing faults are detected by sensing a voltage signal proportional to the rate of change, or di/dt, of the line current when the current steps into an arc fault. A current transformer is used to create the di/dt signal. The transformer has a selected core type, number of windings, and size which saturates at a pre determined level of primary current. The saturation acts to clamp the maximum di/dt voltage signal at the transformer output, and produce a constant output voltage. The constant output voltage eliminates a signal with a high di/dt, which may occur during a lamp burnout, from producing a much larger di/dt signal than that caused by an arc fault at a lower level of step current. The di/dt signal is passed through a high pass filter, which attenuates 60 hz sinusoidal signals, after which the signal is integrated. The integrator acts to delay circuit interruption means until a predetermined number of arcs has occurred.

Abstract: Arcing faults are detected by sensing a voltage signal proportional to the rate of change, or di/dt, of the line current when the current steps into an arc fault. A current transformer is used to create the di/dt signal. The transformer has a selected core type, number of windings, and size which saturates at a pre determined level of primary current. The saturation acts to clamp the maximum di/dt voltage signal at the transformer output, and produce a constant output voltage. The constant output voltage eliminates a signal with a high di/dt, which may occur during a lamp burnout, from producing a much larger di/dt signal than that caused by an arc fault at a lower level of step current. The di/dt signal is passed through a high pass filter, which attenuates 60 hz sinusoidal signals, after which the signal is integrated. The integrator acts to delay circuit interruption means until a predetermined number of arcs has occurred.

Abstract: A phase control switch with an RFI suppression inductor includes a first winding on the inductor in series with a triac. A first capacitor is in parallel across the series combination of the first winding and triac. The switch further includes a second winding on the inductor with a second capacitor connected in parallel across the second winding. When the second capacitor and second winding resonate, a Q rise in flux occurs in the inductor core, intercepting the flux in the first winding to produce a greater voltage drop across the first winding and a corresponding decrease in the rate of current rise in the triac. Fewer turns are needed in the first winding for proper RFI suppression, resulting in a smaller device.

Abstract: A compact high current relay is provided having first and second fixed contacts connected in circuit relationship with the apparatus to be controlled; an elongated bus bar having first and second movable contacts at opposite ends of the bus bar, the bus bar characterized by a stiffness such that upon application of a first predetermined force to the bus bar, between the contacts, the movable contacts both tilt and wipe with respect to the first and second fixed contacts; and a solenoid connected to the bus bar between the first and second contacts for exerting a force on the bus bar greater than the predetermined force.

Abstract: A motor speed controller for a shaded pole ceiling fan motor having low audible noise, includes a burst period generator for generating gating signals of a duration varying between a preselected minimum equal to at least one wavelength of an AC drive signal to the motor, and a maximum equal to a large number of wavelengths, and a controlled switch such as a triac, connected between the power source and fan motor, and having a gate terminal connected to the burst period generator.