Abstract: An electrical control module provides a plastic insert fitting inside a housing and compressed by assembly of the housing lid and base to be held securely therein. Elastic components on the plastic insert are compressed during the assembly provide a secure retention in the face of normal manufacturing tolerances. The plastic insert includes features for attaching electrical components such as electrical contactors, motor starters, disconnect switches, circuit breakers, and overload switches without conventional screw fasteners or the like through channels and elastic detents.

Abstract: An electrical control module provides a plastic insert fitting inside a housing and compressed by assembly of the housing lid and base to be held securely therein. Elastic components on the plastic insert are compressed during the assembly provide a secure retention in the face of normal manufacturing tolerances. The plastic insert includes features for attaching electrical components such as electrical contactors, motor starters, disconnect switches, circuit breakers, and overload switches without conventional screw fasteners or the like through channels and elastic detents.

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 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 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: A control circuit for electrical contactors, starters and the like which include one or more pairs of separable main contacts is controlled by an electromagnet assembly. In order to reduce, if not eliminate, audible noise generated by the electromagnet assembly, the electrical current to the electromagnetic assembly is regulated to minimize the rate of change of magnetic flux therethrough to thereby reduce, if not eliminate, audible noise. By regulating the electrical current to the electromagnet assembly, the power consumption of the electromagnet assembly is reduced which, in turn, reduces undesirable heating of a solenoid coil within the electromagnet assembly.

Abstract: A unique combination of nonvolatile memory (16) with a visual indicator (18) to give a device an address display which adds very little cost or space to the device and its housing. A nonvolatile RAM incorporated into the device electronics is provided with a memory location sufficient for storing the identifier in binary form. A simple visual display in the form of an LED (18) is also provided in the device housing and electrically connected to the RAM for providing visual indication of the stored number according to a predefined code.

Abstract: A method and apparatus are disclosed to reconstruct a third phase for a three phase sensing system in which only two current transformers sense all three phases. Two phases of the three phase system are used as a single primary winding for each current transformer such that each current transformer produces a voltage representation of a sum of two phase currents. The present invention is directed toward reconstructing the third phase from the two discrete signals produced so that true RMS characteristics can be determined, as well as indicating any phase loss. Since all three phases can then be represented, this technique offers precise phase imbalance protection as well.

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: An electronic overload relay has an intrinsic power supply connected in parallel with the NC contact of the relay between wire attachment terminals. The power supply is a parallel connected zener diode and capacitor, connected to the processor in parallel with a low voltage sensing circuit that detects the charge on the capacitor, whereby the processor operates to turn on a unijunction transistor for low voltage coil applications to shunt the power supply during contactor closing and turn off a predetermined interval later by which time the contactor should have closed.

Abstract: A motor starter includes separable contacts; an operating mechanism for operating the separable contacts; an overload relay controller including a memory for storing the settings for a plurality of selectable operating features, and a microprocessor for retrieving the settings from the memory and employing the settings at least for controlling the operating mechanism; and a programmer module temporarily engaging the overload relay controller for changing the settings in the memory.

Abstract: An electrical switching device such as a motor starter includes separable contacts; a coil for operating the separable contacts; two light emitting diode indicators having a plurality of states; a pushbutton switch; and a control circuit responsive to the pushbutton switch employing a plurality of parameters for controlling operation of the coil and the indicators, with the control circuit having a setup mode and including a microcomputer for detecting actuation of the pushbutton switch to enter the setup mode, indicating a first one of the states on the indicators corresponding to a first one of the parameters, and detecting de-actuation of the pushbutton switch to indicate a value of the first parameter on the indicators.

Abstract: A motor starter for an electrical circuit including a power source and a load, includes an electrical contactor having separable contacts for switching an electrical current flowing between the power source and the load, and an operating mechanism responsive to a trip signal for opening and closing the separable contacts; a current sensor for sensing the electrical current flowing between the power source and the load and providing a sensed current value therefrom; and an overload relay including a microcomputer routine for generating the trip signal as a function of a trip current value and at least one of: (a) a test current value, and (b) the sensed current value; and a test routine including at least one of: (a) a first selecting mechanism including a routine for selecting a first predetermined value as the trip current value and a routine for selecting the test current value for use by the microcomputer routine with the trip current value, and (b) a second selecting mechanism for selecting one of at leas

Abstract: An improved contactor control system comprising several modules, such as a contactor module, an overload/controller module, a communication module, a bell alarm module, and a power terminal module which are electrically interconnected through a plug-in unit, and mechanically interconnected through one or more snap-in units, and which modules can be interchangeable and arranged relative to the overload/controller module according to a particular industrial application.

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.

Abstract: An electrical switching device such as a motor starter is adapted to be controlled through control signals in control wiring and includes separable contacts; an operating mechanism for opening and closing the separable contacts; first terminals for interfacing the control signals to the operating mechanism; a modular surge suppressor circuit for suppressing a surge associated with the control signals, with the modular surge suppressor circuit including second terminals for engaging the first terminals and interfacing the control signals thereto; and a modular terminal block for interfacing the control signals in the control wiring to the modular surge suppressor circuit.

Abstract: An electromagnetic switch includes separable contacts, an electromagnet having a coil which is energized to close and hold closed the separable contacts, a power supply for applying current to the coil, and a closed-loop control circuit for sensing and regulating, throughout a contact closure cycle, the current applied to the coil to a selected current reference. The current reference may include a closing current reference for closing the contacts and a holding current reference for holding the contacts closed.

Abstract: An electrical contactor has first and second contacts movably mounted to engage for achieving continuity in an electrical circuit, via an electromagnet and armature defining a magnetic circuit with an air gap that closes in a first position of the contactor and opens in a second position of the contactor. A controller switches an alternating current voltage to the coil of the electromagnet during a timed portion of each AC half cycle, and senses the current level in the coil in a feedback loop. The controller adjusts the voltage-on time to achieve a predetermined average current as needed for accelerating the armature or coasting during a closing operation, for holding the armature in place when closed, etc. In order to sense whether the contactor is presently open or closed, the controller monitors and stores the phase angle between the previous voltage zero crossing and the time of voltage turn-on.

Abstract: An electrical device such as an electrical contactor interfaces at least one alternating current transformer having an output providing a signal proportional to changes in alternating current and includes at least one filter for filtering the output signal of the transformer. Each of the filters have an input connected to the transformer and an output having a signal proportional to the transformer output signal and inversely proportional to selected frequencies of the alternating current. The electrical device also has means for determining a value related to the alternating current using the output of each of the filters. The filter may have a resistor and a capacitor for filtering the transformer output signal in order that the filter is a low-pass filter. Alternatively, the filter may be a band-pass filter.

Abstract: A contactor circuit couples electrical power to a load, and has a current sensor responsive to a level of current for generating an output signal level when the current exceeds a fault threshold. A control circuit coupled to the output signal has a trip output that changes level with the output signal of the current sensor, coupled to its reset input via an indicator circuit, whereby the control circuit is reset when the current exceeds the fault threshold. A bell alarm circuit picks off the trip output for operating an alarm device. The bell alarm circuit has a comparator with an input coupled to a capacitor charged through a resistor and a transistor arranged to discharge the capacitor when the trip output is low. The transistor is responsive to an optical coupler arranged in the indicator circuit in parallel with an indicator LED that is blinked by the control circuit.