Eaton Corporation

Westinghouse Electric Corporation

Thermo King Corporation

Unimation, Inc.

Eaton Coroporation

Staubli International Ag.

Richard A Johnson

Joseph C Engel

Leonard C Vercellotti

Gary F Saletta

Richard J Casler, Jr

Kenneth E Daggett

Eimei M Onaga

James Leo Lagree

Joseph J Matsko

William John Jones

Dirk J Boomgaard

David A Christiansen

Seymour Salowe

Robert Tracy Elms

Jay L Hanson

William John Murphy

Alan B Shimp

Francois Jean Marchand

Norman Davies

Doyle G Herrig

Romuald M Jurewicz

Jayaram Seshadri

Alan D Gustafson

William R Verbanets, Jr

Steven Edward Meiners

Gregory R Truckenbrod

James I Wise

Rajan C Penkar

Lowell B Naley

David M Oravetz

Deborah Kaltwasser Mort

Jeffrey B Berge

Barrett L Booth

Arthur A Anderson

Lane L Woodland

Daphne C D'Zurko

Herbert S Falk

Robert G Colclaser, Iii

John A Massoud

Michael F Boccabella

Francois J Marchand

Protection is provided for servicing a distribution bus by grounding the line side of a circuit breaker through which the distribution bus is fed and then closing the circuit breaker. The trip unit of the circuit breaker includes logic, in addition to the normal protection logic, which opens the circuit breaker main contacts without delay if current is detected upon closing of the grounded circuit breaker. However, if the grounded circuit breaker has been closed for a selected period of time and then current is detected, the distribution bus is kept at zero potential by not operating the breaker. A breaker auxiliary switch with a mechanical delay provides the indication of the selected time interval after closing the circuit breaker.

Apparatus and method for servicing a distribution bus

A network protector includes a coil drive circuit for the trip actuator which operates as a current limiter to protect a trip coil with limited impedance at the upper limit of network voltage while assuring operation at network voltages of less than 10% rated voltage. A comparator provides gate drive current to a FET connected in series with the trip coil as long as coil current is below a reference voltage proportional to a specified maximum value of coil current. When the specified value of coil current is reached, the FET is latched off until the network protector is tripped open again.

Drive circuit for the trip actuator of a network protector and a network protector incorporating the same

A non-automatic power circuit breaker includes separable contacts for movement between a closed position and an open position, and an operating mechanism for moving the separable contacts between the open and closed positions. A time-delayed making current release switch is closed for the open position of the separable contacts and is opened a predetermined time after the separable contacts move to the closed position. A low permeability air core current transformer senses an electrical current flowing in a current conductor for the separable contacts and provides a signal corresponding to the electrical current. An analog trip unit employs the signal corresponding to the electrical current and the making current release switch signal corresponding to the open and closed positions of the separable contacts and provides a trip signal. The analog trip unit includes a comparator for disabling the trip signal when the making current release switch is opened. A low energy trip actuator employs the trip signal for actuating the operating mechanism to move the separable contacts to the open position thereof. A circuit including rectifiers, a voltage regulator and a capacitor powers the low energy trip actuator from the signal of the current transformer.

Non-automatic power circuit breaker including trip mechanism which is disabled after closure of separable contacts

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

The protective relay is primarily energized by a voltage transformer tap on the power circuit. The current transformers that provide the monitoring current to the protective relay also provide an auxiliary power input to the power supply circuit. A switching circuit monitors the input voltage and switches to the current feed to generate the relay supply voltage when the input voltage drops below a predetermined level. In one embodiment the fault tolerant power supply is provided as an optional, modular, add on unit. In a second embodiment, the power supply is an integral part of the protective relay where the current shares a common input between the monitoring and power circuit and the voltage input is common to both the power supply and any metering circuits contained within the protective relay.

Reliable fault tolerant power supply for a protective relay

An electronic trip unit for a circuit breaker having two current sensors per phase, wherein the first magnetic core current transformer is designed to monitor current in the normal and overcurrent range, and the second low-permeability core sensor is designed to produce an override trip signal at or below the short time withstand current rating of the circuit breaker. In a second embodiment the electronic trip unit includes only the low-permeability core sensor that has negligible output in the normal current range.

Electronic trip unit with dedicated override current sensor

A circuit breaker includes separable contacts for movement between a closed position and an open position. An operating mechanism moves the separable contacts between the closed and open positions and has a closed state and an open or tripped state which corresponds to the open position. A trip circuit senses electrical current flowing through the separable contacts, employs the sensed current to trip the operating mechanism to the tripped state to move the separable contacts to the open position, and provides plural status signals. A display circuit cooperates with the trip circuit and includes light emitting diodes for outputting the status signals. A battery powers the display circuit which further includes an oscillator circuit for modulating the LEDs to reduce power from the battery to the display circuit.

Electrical switching apparatus employing battery-powered indicator

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

An electrical switch with overcurrent protection communicates as a slave with a remote master station by sending return messages to the remote master station only in response to messages addressed to it. A portable unit plugs into the electrical switch and disables communications between the electrical switch and the remote master station. The portable unit then establishes communications with the electrical switch by sending a global message to the electrical switch requesting the unique address at successive baud rates until a return message containing the electrical switches' address is received. A communications module in the electrical switch transfers to a master mode in response to the global message in order to send the return message containing its unique address. It then reverts to the slave mode for response to subsequent messages from the portable unit containing the unique address. Either the remote master station or the portable unit can test the circuit breaker by sending a message containing a digital test current to the circuit breaker.

Electrical switches with current protection interfaced with a remote

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

A method of operating a transport refrigeration system having a compressor driven by a prime mover at a selected one of high and low speeds, an evaporator, and an evaporator blower driven by the prime mover. Refrigeration control provides an error value which controls the temperature of a load space to a predetermined set point via heating and cooling modes. The method includes the steps of driving the compressor at high speed during pull down, and injecting hot gas into the evaporator when the error is reduced to a predetermined value. The prime mover is maintained at high speed, to keep evaporator air flow at a high rate, continuing a relatively rapid temperature pull-down across the entire load space. The speed of the prime mover is reduced to low speed when the error is further reduced to a second value, which also initiates suction line modulation while maintaining hot gas injection.

Method of operating a transport refrigeration system

A pulse width modulation (PWM) control circuit provides for improved implementation of position, velocity and current feedback loops for digital servo control of a multi axis robot. The PWM circuit utilizes a single resistor for sensing joint motor drive current. Circuitry is also disclosed for reducing audible noise and motor heating in large servo motors used for joint arms operated at relatively low PWM frequencies by reducing the motor ripple current.

Digital robot control having pulse width modulator operable with reduced

A digital control for a multiaxis robot includes position, velocity and torque controls that drive a motor voltage control loop. Pulse width modulated control signals operate power switches in a power bridge to control the current to each robot joint motor. A single resistor is connected in the bridge circuit to supply motor current feedback needed for control loop operation.

Digital robot control having an improved current sensing system for

The present invention provides a precision variable gain current-to-voltage amplifier which has a test mode of operation wherein the gain is independent of the gain of the amplifier when operated in the normal amplification mode. The invention enables a test signal, preferably a test voltage, to be injected into the amplifier circuit to test the functioning of the op amp and thus the amplifier. Because the gain of the amplifier in the test mode is independent of the gain of the amplifier when in the normal mode, a simple and easy method of checking the functioning of the op amp is provided which does not require knowing the gain of the amplifier and then selecting the proper test input to use.

Variable gain current-to-voltage amplifier with gain independent test

Growing community of inventors

Murrysville Boro, PA, United States of America

Richard A Johnson