Abstract: A solid state overload relay utilizes an apparatus that converts the current of a polyphase electrical load to a voltage signal approximately proportional to the RMS current of the load. In addition to providing the overload function, the voltage signal is used to provide an improved phase current unbalance protection. Conventional current transformers sense the current flow in each phase of the load. The current waveform for each phase is converted to a voltage by rectification and the peak value and the average value of the resultant voltage is determined. A summing circuit combines the two values at a predetermined ratio to create a DC voltage that is approximately equal to the rms value of the input phase current. A combination of the approximation circuit with a time integrating circuit and a level detecting circuit produces a low cost solid state overload relay in one embodiment of the invention.

Abstract: A circuit for detecting phase imbalance in a three phase electrical system. The circuit includes a three phase current transformer or three separate current transformers for monitoring the current flowing in each phase of a three phase electrical system. The current transformers provide an induced current proportional to the monitored current. The induced current passes through a full-wave bridge rectifier which produces a voltage output proportional to the induced current. This voltage signal is passed to a two pole Sallen-Key filter which allows a desired signal having a particular frequency range to pass through and blocks the passage of an undesired signal having a particular frequency range. A scaling circuit then receives a portion of the desired signal and produces a scaled average signal which is of a preselected magnitude lower than the desired signal.

Abstract: A proximity switch circuit including first and second transistors Q4, Q6 connected as a long tail pair with an inductive sensing circuit LC connected to one leg thereof and an emitter follower circuit Q7, Q8 connected between said one leg and the base of the transistor of the other leg, whereby an oscillator circuit can be provided which is non-critically damped to enable faster speed of operation of the proximity switch.

Abstract: The present invention provides an integrator 5 with switched hysteresis for inductive proximity switches comprising a reference current source IREF connected between a reference voltage supply rail and a first side of a current mirror, a second side of the current mirror being connected to a proximity switch rectifier, the first side of the current mirror being connected to a capacitor CINT and to one input of a two input comparator, the other input of the comparator being held at a threshold level, wherein a fixed hysteresis current source IHYST is provided in parallel with the current reference source IREF, the fixed hysteresis current source IHYST producing a switchable current which is a fixed proportion of the current of the current reference source IREF, the fixed hysteresis current source IHYST being switched on (off) when a target is detected and off (on) when no target is detected. This invention provides for reduction of effects detrimental to the speed of operation of the switch.

Abstract: The invention discloses a vacuum contactor assembly for controlling current flow in a single or multi-phase electrical circuit wherein each phase of the electrical circuit is controlled by a single vacuum interrupter. The stem pressure or pressure exerted on the electrical contacts of each vacuum interrupter during and after closing may be individually adjusted to an optimum operating pressure. The individual interrupter stem pressure adjustment is accomplished by placing a spring and an adjustment nut on the stem screw between the operating arm and the interrupter stem. By adjusting the free length of the spring with the adjusting nut, the interrupter stem pressure may be controlled.

Abstract: An enclosure for electrical or electronic devices having components requiring periodic adjustment is provided with an access opening to the adjustments for the components including a hinged, attachable door for closing and sealing the access opening.

Abstract: A machine operator control station circuit which uses capacitive proximity switches to replicate the function of mechanical switches used in prior art control stations. A monitoring circuit for monitoring the "on" state of the capacitive proximity switches used in a two hand industrial machine control station is disclosed. The circuit also reduces the chance of unintended operation of the machine being controlled as a result of emitted or conducted radio frequency interference which might be detected by the capacitive proximity switches. An isolation transformer provides an isolated power supply for the monitoring circuit. The monitoring circuit includes a first capacitive proximity switch for detecting the presence of one of the machine operator's hands, and a second capacitive proximity switch for detecting the presence of the other of the machine operator's hands. Each proximity switch has a monitoring circuit for monitoring the length of time the proximity switch remains in the activated or "on" state.

Abstract: The present invention discloses an apparatus for adapting an electronic or electrical device enclosure for mounting on a DIN mounting rail having two opposed outwardly extending flanges. The apparatus comprises a DIN mounting rail bracket having provisions for attaching to the enclosure of the electrical or electronic device. The mounting rail bracket is provided with a hook for receiving a portion of one of the outwardly extending flanges of the DIN rail. The mounting rail bracket is also provided with a selectively operable locking and releasing mechanism opposite the hook for locking onto and releasing from a portion of the other outwardly extending flange of the DIN rail.

Abstract: A stackable multi-directional indicator light for displaying the ON/OFF status of a miniature switch such as a limit or stackable switch. The miniature switch includes a switch mechanism for making and breaking an electrical circuit, an actuator for actuating the switch, and a wiring cable for providing the electrical circuit. The multi-directional indicator light includes an indicator light source connected to the switch mechanism, and a cover/lens for displaying light emitted from the indicator light when the switch is in the ON state. The indicator light is mounted in the cover/lens which is made from a light transmissive material. The switch mechanism, indicator light source, and cover/lens are mounted on a base made from a material of suitable strength to provide support and protection. The base and cover/lens provide physical protection for the indicator light and the switch mechanism. The base also includes a passage for retaining the actuator and permitting it to communicate with the switch mechanism.