Abstract: Methods and system for sensing current include detecting current through a sensing coil resulting from a field produced by current through a primary conductor. The sensing coil has a core that may become saturated by the primary current field. If the core is not saturated, a sensing circuit may detect the current through the sensing coil by changing the state of at least one controlled switch. If the core is saturated, the sensing circuit changes the state of the at least one controlled switch to pull the core out of saturation, at which time a current measurement is made. The technique may be used with AC currents, including changing currents, as well as with DC currents, and currents that may be AC at times and become essentially DC at other times.

Abstract: Systems, methods, and devices are disclosed, including an induction-motor controller that has a motor controller configured to receive alternating current (AC) power with a voltage that varies generally sinusoidally and transmit the AC power during a conduction angle of a cycle of the AC power. In some embodiments, the conduction angle varies generally sinusoidally at a lower frequency than the AC power, and the motor controller may be configured to not transmit the AC power outside of the conduction angle.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: A sensing and switching device, such as an overload relay, is provided which includes a processor configured to make measurements and control operation (e.g., tripping) of the device. The processor regulates measurement of voltage and/or current, and the supply of power to power supplies. The power supplies store charge to provide operational power for the processor and that can be used for tripping and resetting contacts within the device. The processor opens a burden resistor measurement circuit when charge is being stored in the power supplies, and opens switches in the power supplies while closing the burden resistor switch to permit measurements. By alternatively switching for charging of the power supplies and making of measurements, the processor is able to reliably make measurements, control the device, and store sufficient power for operation of the device despite a demanding power budget.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: A sensing and switching device, such as an overload relay, is provided which includes a processor configured to make measurements and control operation (e.g., tripping) of the device. The processor regulates measurement of voltage and/or current, and the supply of power to power supplies. The power supplies store charge to provide operational power for the processor and that can be used for tripping and resetting contacts within the device. The processor opens a burden resistor measurement circuit when charge is being stored in the power supplies, and opens switches in the power supplies while closing the burden resistor switch to permit measurements. By alternatively switching for charging of the power supplies and making of measurements, the processor is able to reliably make measurements, control the device, and store sufficient power for operation of the device despite a demanding power budget.

Abstract: A current measurement technique is disclosed in which a family of transformer coils having the same number of turns and the same winding resistance may be associated an active circuit for presenting a burden resistance of substantially zero value. The impedance of the coils will vary with their window size, and the active circuitry will reduce the burden resistance accordingly so that reductions and impedance do not result in introducing additional error into measurements. The circuitry may be used for measuring current in single conductors or in multiple conductors passing through the transformer coil, such as for ground fault measurement, monitoring and control.

Abstract: Systems, methods, and devices are disclosed, including a ground-fault sensor that has a plurality of conductors each disposed one inside of another except for an outer conductor and a field sensor configured to sense an electric field, a magnetic field, or both. In some embodiments, the field sensor is disposed adjacent the outer conductor.

Abstract: Systems, methods, and devices are disclosed, including an induction-motor controller that has a motor controller configured to receive alternating current (AC) power with a voltage that varies generally sinusoidally and transmit the AC power during a conduction angle of a cycle of the AC power. In some embodiments, the conduction angle varies generally sinusoidally at a lower frequency than the AC power, and the motor controller may be configured to not transmit the AC power outside of the conduction angle.

Abstract: A technique for reducing nuisance tripping is disclosed in which a desired limit temperature is determined for a component of a motor system. The limit is compared to actual temperature signals, or signals indicative of temperature of the component. The component may be the conductor or conductors providing power to the motor. A counter is augmented when the actual temperature exceeds the limit. The limit may be computed, such as based on a heating model. A trip signal is generated only when the actual temperature has exceeded the limit for a predetermined number of periods. The counter may be reset if the actual temperature drops below the desired limit.

Abstract: A current measurement technique is disclosed in which a family of transformer coils having the same number of turns and the same winding resistance may be associated an active circuit for presenting a burden resistance of substantially zero value. The impedance of the coils will vary with their window size, and the active circuitry will reduce the burden resistance accordingly so that reductions and impedance do not result in introducing additional error into measurements. The circuitry may be used for measuring current in single conductors or in multiple conductors passing through the transformer coil, such as for ground fault measurement, monitoring and control.

Abstract: A technique is provided for controlling operation of motors of different sized or ratings. Components used to apply and interrupt current to the motors may be shared in control devices for the different motors. The components may include contactors or circuit interrupters, and instantaneous trip devices. The components may be sized for the higher rated motors, and be oversized for the lower rated motors. Control circuitry permits the devices to be controlled in accordance with the characteristics of the particular motor to which the devices are applied, providing accurate circuit interruption while reducing the number of different components and component packages in a product family for the various motors.

Abstract: A sealed modular control and monitoring system is provided which affords location of electrical control and monitoring components adjacent to an application. The system comprises modular components which are mounted on a shared thermal base. The base is sealed to the components and presents thermal exchange features on interior and exterior surfaces thereof. Forced convection within the modular system is afforded by a circulating fan that directs air through the component circuitry and adjacent to the thermal base to remove heat from the circuitry during operation.

Abstract: A technique is provided for controlling and protecting loads such as electric motors. In the technique, current sensing circuitry detects electrical current applied to the load. Device thermal modeling circuitry, such as circuitry for modeling heating of a motor, determines heating based upon the sensed current, and generates a first trip signal in a first range based upon the current. Conductor thermal modeling circuitry estimates heating of conductors that supply current to the load, and generates a second trip signal in a second range based upon the conductor heating. The system provides an extended range of operation for a wide range of loads by effectively modeling conventional thermal overload and instantaneous trip devices.

Abstract: A motor control technique is disclosed in which a first algorithm controls interruption of power to a motor in a first current range. A second algorithm controls interruption of power in a second, higher current range. The algorithms may be adapted to specific motor sizes, ratings or classes. The extended range may extend from a transition point (e.g., 6–10 times the FLC of the motor) to an upper limit. The upper limit may be determined based upon a current rating of an instantaneous trip device.

Abstract: The dynamic range of a current transformer (CT) is increased without reducing the scaling of measurements at the low end of the dynamic range by designing the core of the CT to saturate only after about 90 electrical degrees of the maximum current to be measured. The measurements taken during this first 90 electrical degrees before the core saturates are doubled to in effect add measurements representing the mirror image of the first 90 electrical degrees. Timing of the digitized samples taken during the first 90 electrical degrees is adjusted to account for core reset energy errors, by determining the rate of change of current just after a zero crossing and selecting an empirically determined value of current for timing the start of the measurement samples.