Abstract: A motor overload coil control is disclosed for use in a motor starter/relay contactor. The control includes an 8-bit, 8-pin microcontroller that together with an I/O reduction circuit, is capable of functioning 13 I/O's with only 5 I/O pins on the microcontroller. Three remote signals are prioritized and reduced on one input line to the microcontroller. The control includes three-phase current measurement from three Hall effect current sensors positioned one on each leg. The system includes current integration to provide a single current input to the microcontroller. A full load amperage (FLA) adjustment allows use on a wide range of motors. The microcontroller uses the FLA adjustment and the current signal to find an appropriate I2t value for real-time monitoring of the operating temperature of the motor. A status indicator is provided having an LED output to show the status of the system and indicate the motor temperature, when appropriate.

Abstract: A heat sink is slideably attached to a housing of an electronic control, retained by complemental snap-in elements and has a projection extending through a wall of the housing into abutting thermal engagement with an internal heat sink which is in intimate contact with the electronics of the control.

Abstract: A molded insulating collar for an insulating housing of a circuit breaker has a plurality of depending tabs which are received in grooves in the housing and provided with cooperating snap-fit structures within the housing to enable the collar to be sub-assembled to a circuit breaker. Collars are removable and replaceable in the field.

Abstract: Photoelectric reflective object sensors are mounted in an exteriorly mounted auxiliary switch case to detect a member on a movable contact assembly of the contactor to produce logic level output signals indicative of the operational state of the contactor electromagnet. One or a pair of photoelectric sensors are used in a side mounted auxiliary switch to detect the contactor movable contact assembly in the energized or de-energized position, or en route between the two positions. A single photoelectric sensor is used in a top adder auxiliary switch to detect if the movable contact assembly is or is not in the extended (de-energized) position. The auxiliary switches provided logic level output signals directly usable with microprocessor based controllers.

Abstract: A planar transformer having windings on a printed circuit board coupled by a high frequency ferrite core driven by a high frequency operational amplifier based relaxation oscillator controlling a switch for pulsing a primary winding of the transformer at a set frequency. The secondary of the transformer powers a lamp circuit which is isolated from the electrical supply, and a test input is connected in a logic OR arrangement with the electrical supply.

Abstract: A pair of pivoted links positioned at opposite sides of a movable armature and reversely oriented with respect to each other, have a pivotal connection at their opposite ends to a movable contact carrier and intermediate their ends to the armature whereby movement of the armature is amplified in movement of the contact carrier to permit reduction in the air gap between the armature and electromagnet core without incurring a corresponding reduction in contact carrier movement.

Abstract: A pre-engineered single-rated combination starter is suitable for controlling any size motor ten horsepower and below in a three-phase 460 volt system. The assembled starter comprises an electronic overload relay having current sensors which do not carry motor current, a contactor and fuses sized for the ten horsepower motor, wire conductors sized corresponding to the fuse size, and an installation specification to use that specific size wire for connection with the motor.

Abstract: A coil is inherently aligned with the open face of a cup core and prevented from recessing into the core upon assembly of the coil and core into a housing by placing a resilient foam washer within the core under the coil to cause the coil to normally extend beyond the open face of the core and subsequently securing the subassembled core and coil pressed against a common internal surface of the housing, compressing the foam washer. Internal tabs on the foam washer are compressed between the center boss of the cup core and the internal surfaces of the coil opening to retain the coil assembled to the core as a separate subassembly.

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: In an electro-optic voltage transducer utilizing a crystal exhibiting birefringence in a fast axis and a slow axis mutually orthogonal to an optic axis in the presence of an electric field produced by the voltage to be measured, the crystal is mounted for angular adjustment relative to the direction of propagation of a light beam passing through the crystal and polarized at an angle to the fast and slow axes to provide adjustment of the effective half-wave voltage of the crystal. Preferably, the crystal is a disk mounted for rotation about an axis perpendicular to the optic axis by temperature sensitive mounts extending perpendicular to radii of the disk in order to provide temperature compensation. Greater angular adjustment, which extends unambiguous voltage measurement above the natural half-wave voltage of the crystal, is provided by securing the temperature responsive mounts to a rotatable support disk.

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: A thick solid steel slot motor is disposed adjacent a movable conductor to apply a contact closing force on the conductor, augmenting the contact pressure spring, under steady state current conditions, and to reduce the force under high rate of current rise conditions to enhance dynamic separation of the movable conductor from a stationary conductor, reducing the strength requirement of the contact pressure spring.

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: A starter comprising a contactor with an overcurrent relay provides an appropriate cooling interval for each of multiple classes of a load, such as a motor. An analog equivalent of a digital I.sup.2 t value calculated by a microcomputer in the overload relay is maintained by an external capacitor. When the microcomputer loses power following a trip, the capacitor discharges through a resistor at a rate selected to mimic cooling of the associated class of the load. Restart of the load is prevented until the appropriate interval, represented by the time required for the voltage on the capacitor to decay to a common reset value, has expired. The capacitor is charged to a voltage proportional to the I.sup.2 t trip value for the particular class of the load, which for all classes is below the forward drop of the clamping diodes on the microcomputer inputs to prevent discontinuities in the timing.

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 controller for an electrical switching device such as a motor starting contactor including separable contacts, an operating mechanism for operating the separable contacts and a control mechanism responsive to a plurality of control sources for controlling the operating mechanism, includes a plurality of light emitting diode indicators each of which corresponds to one of the control sources; a membrane pushbutton; and a selection circuit, responsive to the pushbutton for selecting one of the control sources, including a circuit for detecting actuation of the pushbutton; a circuit responding to the actuation for sequentially indicating representations of at least some of the control sources on the corresponding ones of the indicators; and a circuit for detecting de-actuation of the pushbutton to select one of the control sources the representation of which is indicated on the corresponding one of the indicators at the time of the de-actuation.

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: In a molded case circuit breaker with an interchangeable thermalmagnetic trip unit, the C-shaped heater transformer core is permanently held in place in the casing by a load bus strap with the gap in the core facing the trip unit. When the interchangeable trip unit is inserted into the molded casing, a magnetically permeable member mounted in the trip unit is aligned in the gap in the heater transformer core. The bimetal of the trip unit is fixed at one end to an electrically conductive sleeve surrounding the magnetically permeable member and forming the secondary of the heater transformer. The length of the magnetically permeable member is selected to establish the current conditions at which the bimetal trips the circuit breaker.

Abstract: A molded insulating connector body is pinned to the housing of an electrical device such as a switch, indicating light, instrument, gauge or the like to selectively provide a particularly keyed connector body to devices of the same type by a pin which extends through holes in the device terminals and correspondingly aligned openings in the connector body. The pin is retained in place by a collar which envelopes the electrical device body and is threadably attached thereto.

Abstract: A contactor has an armature, a pull-in coil and a holding coil. When the system is energized through a first switch such as a thermostat, the low current holding coil is energized in preparation for holding the armature pulled in after the pull-in coil is energized and the armature has finished its power stroke. A solid-state switching device and the pull-in coil are connected in series between both terminals of a power source. A control circuit causes the solid-state switching device to be conductive the instant power is supplied to the circuit through the first switch. One embodiment of the control circuit is based on logic gates. RC circuits associated with the gates keep the solid-state switching device and pull-in coil conducting long enough for the armature to pull-in. After the solid-state switching device turns on, the transistor is controlled to turn off, deenergizing the pull-in coil while the holding coil holds the armature in until the first switch opens and power input is discontinued.