Westinghouse Electric Corporation

Eaton Corporation

North American Philips Lighting Corp.

Gary F Saletta

Joseph C Engel

Robert Tracy Elms

Joseph J Matsko

Richard A Johnson

Denis A Mueller

Alan B Shimp

Bernard J Mercier

John G Leddy

John A Wafer

William John Murphy

William E Beatty, Jr

Edward C Prather

John T Wilson

Clyde O Peterson

Robert J Spreadbury

Marlan L Winter

Raymond O Whitt

Daniel P Orange

John M Hicks

Patrick J Hunter

An electronic trip unit having two microprocessors one of which monitors the load voltage and current within the normal operating range and performs the metering and delayed trip algorithms associated with that range. A second microprocessor monitors the load current for excursions outside the normal operating range and processes those algorithms and functions associated with the instantaneous and overcurrent trip protection modes of the trip unit. Each microprocessor receives inputs representative of the monitored current that are scaled to a different factor corresponding to the range the microprocessors are assigned to monitor. In one embodiment the electronic trip unit is controlled by a master controller and in turn controls a number of accessory devices, wherein one of the microprocessors is a slave to the master controller network and the other microprocessor is a master to the accessory slave network. The microprocessors communicate with each other and either one can trip the circuit on detection of a fault condition.

Dual microprocessor electronic trip unit for a circuit interrupter

A circuit interrupter samples waveforms in a protected circuit by taking samples in pairs spaced 90 electrical degrees apart. The sum of the squares of samples in each pair, which is representative of the RMS value of the fundamental frequency of the waveform, is used for instantaneous protection by comparing a running sum of the squares for the two most recent pairs of samples to a threshold representative of the instantaneous trip pick-up value. This sum of the squares of successive two pairs of samples is also used for short delay protection. A delay between successive pairs of samples is varied to produce a selected equivalent sampling rate after a given number of samples. Samples accumulated at this equivalent sampling rate, which is sixty-four samples per cycle in the preferred embodiment, are used for long delay protection and metering.

Apparatus providing protection and metering in an ac electrical system

A circuit breaker with a digital trip unit has a protection mode and a waveform capture mode of operation. In the protection mode, an equivalent sampling technique based upon pairs of samples spaced 90 electrical degrees apart with a pattern of delays between pairs is used to digitize the waveforms in the protected electrical system. Synchronous sampling is used in the waveform capture mode. The value of each sample is monitored in the waveform capture mode and a transfer is made back to the protection mode if a threshold value indicating an overcurrent condition is exceeded. The percentage total harmonic distortion, and per harmonic distortion for harmonics, up to and including the 27th are sequentially presented on a display on the front panel of the circuit breaker and can be transmitted along with the raw waveform data to a remote processor.

Circuit interrupter providing protection and waveform capture for

A circuit interrupter with a digital trip unit automatically sets the sampling interval appropriate for the 50 Hz or 60 Hz distribution system to which the interrupter is connected. In order to avoid falsely shifting the interval in response to distorted currents, the trip unit only changes the interval if the number of zero crossings of the current within a fixed number of samples is within two zero crossings of the number of zero crossings for an undistorted current of the other frequency for two consecutive time periods in which the fixed number of samples are taken. Furthermore, changes in the interval are only written into an EEPROM for use on power-up a fixed number of times to preclude disabling the EEPROM. In one embodiment, a 2 pole filter is utilized in the zero crossing counting circuit to eliminate false counts from noise originating in a chopper used in the trip unit power supply. In another embodiment, the zero crossing counting circuit is disabled unless external dc power is available for the trip unit which idles the chopper.

Digitally controlled circuit interrupter with improved automatic

In a multiple contactor installation where each contactor provides overcurrent protection, overload information in passed from one active contactor to the next as a percentage of the trip level of the respective contactors.

Electrical contactor system with transfer of scaled overload information

A microprocessor based switch such as a circuit breaker generates digital rms representations of analog load currents from n samples of the analog currents per cycle synchronized to the line frequency, where n is an odd integer equal to a selected highest order harmonic to be detected plus 2. A routine determines whether the power system is 50 or 60 Hz, and automatically sets the sampling interval to provide exactly n samples per cycle for the connected source. Terminals for rapidly resetting an analog memory for calibration and field testing of a long delay trip are hidden behind a removable rating plug.

Electrical switching apparatus with digital trip unit and automatic

A graphical representation of the current/time trip characteristic displayed on the operator's panel of an electronic trip unit for a circuit interrupter, has different indicia, such as different colors, identifying the representation of independent trip functions from those of dependent trip functions, thereby making the operator aware that adjustment of one of the dependent trip functions will also affect an adjustment of the other dependent portions of the current/time trip characteristic.

Overcurrent trip unit with indication of dependency of trip functions

Process and apparatus for calibrating an electrical device such as a circuit breaker, motor controller or monitor is taught. A precision power supply device is interconnected by way of appropriate input channels to the device to be calibrated for supplying a precise accurate calibration variable as an input. A personal computer PC is interlinked by way of a communications network with the apparatus to be calibrated and is also interlinked with the precision supply device so that the personal computer PC has available the exact value of input variable utilized. Gain adjustment calibration is made by supplying the predetermined value of circuit variables, for instance 10 amperes or 120V to the input terminals of the device being calibrated. Upon command, the personal computer PC instructs the device being calibrated to deliver to the personal computer PC those values of input variable which the device being calibrated interprets as the input variable value. The personal computer PC compares this value with the actual value and generates a correction factor which the personal computer PC sends back to the device being calibrated for storage in an EEPROM. Consequently, during subsequent use after the calibration procedure has been completed and the calibration features have been safely 'locked' away in the EEPROM, all readings will be adjusted by the aforementioned calibration factor to compensate for errors which may exist in other portions of the device being calibrated.

Process for auto calibration of a microprocessor based overcurrent

The coil of an electromagnetic contactor is controlled by a microcomputer which stores control data in an internal RAM memory. An integrated circuit chip provides a tightly regulated +5 volt supply voltage to the microcomputer and generates reset signals on power up and power loss. A logic circuit distinguishes a power loss reset from a power up reset and transfers the microcomputer to a STOP mode in which only the RAM is energized to retain the control data. Reserve power to energize the RAM during a power loss of up to several minutes in duration is provided by a large capacitor which is kept charged by the regulated +5 volt supply. Voltage on the capacitor is checked through the integrated circuit on power up to determine if sufficient voltage was maintained to assure the integrity of the RAM.

Microcomputer controlled electric contactor with power loss memory

In a compressor system, surge detection is provided by sensing the current of the motor driving the compressor and reading oscillations of the current about the average thereof and above and below two opposite threshold levels from such average current and counting the polarity changes within a time interval containing so many samples of the current and defining a sliding window.

Compressor surge detection system

A circuit interrupter includes a circuit arrangement for sampling a conditioned current value and determining operating characteristics related to the current flow through an electrical circuit. Also included is a circuit arrangement for comparing the operating characteristics to preselectable tripping parameters and circuit arrangement for initiating a trip condition when an operating characteristic exceeds a corresponding tripping parameter. Additionally, a circuit arrangement for selecting and displaying operating information in an understandable format and in an easily accessible position on the circuit interrupter is also included.

Circuit interrupter apparatus with a selectable display means

A bidirectional motor has two electromagnetic contactors, one for forward, the other for reverse operation. Thermal protection is provided by a thermal image generator and a thermal protection unit in each contactor operating in tandem via a bidirectional line of communication keeping the thermal images in parallelism by one active contactor 'talking' to the inactive contactor, the 'listener'.

Electromagnetic contactor tandem control system for thermal protection

A circuit interrupter includes a circuit arrangement for sampling a conditioned current value and determining operating characteristics related to the current flow through an electrical circuit. Also included is a circuit arrangement for comparing the operating characteristics to preselectable tripping parameters and for initiating a trip condition when an operating characteristic exceeds a corresponding tripping parameter. Additionally, a circuit arrangement for establishing a ground fault current limit using a minimum number of components to achieve a wide range of possible settings, is also included.

Circuit interrupter apparatus with a style saving rating plug

A circuit interrupter includes a circuit arrangement for sampling a conditioned current value and determining operating characteristics related to the current flow through an electrical circuit. Also included is a circuit arrangement for comparing the operating characteristics to preselectable tripping parameters and for initiating a trip condition when an operating characteristic exceeds a corresponding tripping parameter. Additionally, a circuit arrangement for initiating a hardware override trip condition using a minimum number of components upon sensing an override signal, is also included; the override signal representing a limit selectable from a range of values.

Circuit interrupter apparatus with a style saving override circuit

A motor controller system is taught in which an overload relay board utilizes a current monitor which produces an output signal which is related to the current being sensed thereby over a wide range of currents which may vary for instance between 1 and 1,000 amperes. This indicative signal is converted to a DC voltage level which is then provided to the analog-to-digital portion of a microprocessor for being converted to a digital number for being processed by the microprocessor for causing the contacts of the motor controller to open at appropriate current values. The system utilizes an integrating capacitor which samples the output current from the sensor 32 times in succession providing a voltage which is proportional to the line current. This voltage which may exceed the input voltage level of the analog-to-digital converter is nevertheless supplied to the analog-to-digital converter and sampled internally by the microprocessor at double the line cycle time period until the 32 samplings have expired. If at any time during this doubled sampling process the output of the analog-to-digital converter digitally saturates, the left shifting technique is provided with other memory locations within the microprocessor to provide an approximate double value of voltage so that at the end of the 32 line half cycles a very close approximation of the actual current is contained within storage locations within the microprocessor for effective utilization thereby.

Growing community of inventors

Penn Township, Westmoreland County, PA, United States of America

Gary F Saletta