摘要:
An arc fault circuit interrupter includes separable contacts, a neutral conductor, an operating mechanism structured to open and close the separable contacts, at least one current sensor structured to sense current flowing through the separable contacts and output a sensed current value; and a processor. The processor includes a first routine structured to provide parallel arc fault detection, a second routine structured to provide series arc fault detection, and a third routine structured to enable the first routine and disable the second routine for a predetermined time when the sensed current value is greater than a predetermined value and to enable the second routine and disable the first routine for the predetermined time when the sensed current value is less than the predetermined value.
摘要:
A circuit breaker for locating an arc fault for a protected circuit includes separable contacts interrupting the protected circuit and an arc fault detector determining an arc fault in the protected circuit. An analog to digital converter circuit measures a value of peak arc current at the arc fault detector. Another analog to digital converter circuit provides a peak line-to-neutral voltage. A memory provides an arc voltage operatively associated with the value of peak current. A microprocessor determines a distance from the arc fault detector to the arc fault from the value of peak arc current, a wire resistance per unit length or a wire conductance per unit length, the peak line-to-neutral voltage and the arc voltage.
摘要:
A trip unit for a circuit interrupter includes a power supply, a plurality of input terminals and a plurality of output terminals. A heater conductor is electrically connected between each pair of the input and output terminals. The heater conductor is adapted to generate heat responsive to current flowing through the conductor. A diode is disposed proximate each of the conductors for heating thereby. The diodes are electrically interconnected with the power supply and are adapted to provide a forward voltage representative of the temperature of the corresponding conductor. Another diode is electrically interconnected with the power supply and is adapted to provide a forward voltage representative of ambient temperature. A thermal trip circuit generates a trip signal for the circuit interrupter responsive to the forward voltage of the diodes.
摘要:
Series arcs in an ac circuit are discriminated from other phenomenon by analyzing the timing between pulses in a second derivative of the current signal. A first timer starts timing upon detection of a first pulse in the second derivative of current signal. Time out of the first timer starts a second timer which times a second interval or window during which a series arcing fault will generate a second pulse of opposite polarity to the first pulse. Detection of the first pulse followed by a second pulse of opposite polarity during the window sets a flip-flop to record the event. When a predetermined number of events are counted by a counter within a given time-period set by a third timer, an output signal indicating an arcing fault is generated. If the second pulse is generated before the window opens, or a third pulse occurs during the window, the flip-flop cannot be set so that other events such as the switching of a dimmer do not generate a false output signal.
摘要:
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.
摘要:
A contactor includes two DC sensors within the housing which are isolated from the tripping unit, from the power supply and from each other by the combination of a transformer and photoelectric coupling, the sensed signals being pulse width modulated and demodulated on the respective sides of the photoelectric coupling barrier.
摘要:
An electromagnetic contactor or controller is taught in which the voltage which is impressed across the electromagnetic armature winding is controlled with an algorithm to enhance the closing operation. A microprocessor is utilized to implement the algorithm.
摘要:
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.
摘要:
Long conductors in a common cable which interconnect control pushbuttons to the basic control circuit for an electromagnetic contactor often have distributed capacitance between them. This distributed capacitance may conduct capacitive current from the power supply line to a parallel control line. This current interacts with high impedance in the control circuit for producing a voltage, or False signal, which may be of a magnitude which would otherwise be supplied by an ON pushbutton. In order to discriminate between a TRUE signal and a False signal the first capacitor is connected between the power supply conductor in system common and a second capacitor, larger than the first capacitor, is connected between a signal conductor and system common so that under normal circumstances the alternating voltage on the second conductor lags the alternating voltage on the first conductor by an amount .DELTA. except when the voltage on the second conductor is provided by the capacitive current between lines in which case the voltage on the second conductor will lead the voltage on the first conductor by an amount .gamma. due to the capacitive nature of the current. The microprocessor is conditioned to look at the two voltages immediately after the voltage on the first conductor changes state to determine if the signal is produced by a closed pushbutton or capacitive current.
摘要:
Unitary light source comprises compact HID lamp and starting and operating circuit therefor operable from household AC energizing potential. The HID lamp is ballasted by incandescent filament means which also provides the major portion of developed light during HID warm up and after power interruption. The ballast filament and input terminals of a full-wave rectifier connect in series across the light source input terminals and the HID lamp connects across the rectifier output. A low-impedance path means and high-voltage pulse generator, which includes a high-voltage electrode operatively associated with the HID lamp, connect across the rectifier input. Initially, the voltage developed across the rectifier input is relatively high and the pulse generator and low-impedance path means are responsive thereto to devleop high voltage pulses and also provide a low impedance path in series with the ballast filament to cause it to incandesce brightly. The developed high voltage pulses applied to the high voltage electrode ionize the atmosphere within the HID envelope. After the HID lamp starts, the voltage develped across the rectifier input is insufficient to energize the low-impedance path means and pulse generating means. As the HID lamp warms up, the brightness of the incandescent ballast filament means decreases. A lamp keep-alive comprising a DC source is connected across the rectifier means output terminals to provide lamp operating energy during periods of rectifier conduction minima and, if necessary, to provide DC energy as a lamp starting aid.