Showing papers on "Current sensor published in 1973"

Charge control means for motive power battery charger

Abstract: A battery charger is equipped with a current adjusting device. A current sensor continuously measures the current output from the charger and feeds the readings to a current comparator. The terminal voltage of the battery is also continuously read and the readings are fed to a voltage comparator. A voltage reference feeds a constant reference voltage to the voltage comparator. The voltage comparator compares the battery voltage with the reference voltage and feeds a signal dependent upon the voltage difference and in accordance with a preselected program to a current reference. The current reference delivers a signal dependent on the output of the voltage comparator and in accordance with a preselected program to the current comparator. The current comparator to the the signal received from the current sensor tothe signal received from the current reference and provides an output signal to cause the current adjusting device to adjust the charging current to the values called for by the preselected program. A typical charge program which can be selected is a first charging mode at the initial charge rate of the battery until the battery voltage rises to a preselected value slightly below the gassing voltage. This is followed by a second charging mode wherein the charging current is gradually diminished so as to hold the voltage constant at the preselected value. When the charging current drops down to the finishing rate of the battery, a third mode commences wherein the current is held at the finishing rate regardless of further increase of the battery voltage. The charge can be terminated by a timing device set for total charge time or alternately for a predetermined charge period at the finishing rate.

Monitor system for ground fault relay

Abstract: A ground fault responsive protection system having a ground fault trip relay operable by a ground fault current sensor for operating a circuit interrupter when the ground fault current reaches a pre-established trip level and a monitoring system operable for testing the operation of the ground fault trip relay with selective operation of the circuit interrupter.

Sector flux null current measuring apparatus and method

Abstract: A high current measuring apparatus and method is disclosed. In very high current applications, such as in the manufacture of chlorine gas, a measurable field is established around a currentcarrying bus. A field-measuring device, such as a Hall device, is located within the field surrounding the current-carrying bus. This field-measuring device is disposed between two fieldconcentrating elements which concentrate the field passing through the device. Electrical signals from the field-measuring device are amplified by a high-gain amplifier whose output is applied to coils wound around the field-concentrating elements. The current in these coils is operative to reduce or to null the field passing through the field-measuring device. The steadystate current in these coils is proportional to the current in the bus. By passing a known current through the bus or by measuring an unknown current with another already calibrated current-measuring device, the measured coil current can be directly calibrated to bus current. After calibration, the previously calibrated current-measuring device is removed.

Controllable current source

Abstract: A circuit for providing a current the magnitude of which is determined by an externally generated control signal and which is substantially independent of the impedance of the load to which the current is applied. A current generating network generates an output current in accordance with the algebraic sum of the control signals applied to the inputs thereof. One of these inputs is energized by an externally generated control signal which sets the desired value of output current. A second of these inputs is controlled in accordance with a feedback signal indicative of the output current to assure that attempted deviations of the output current from the desired value are counteracted before they substantially affect the level of current through the load.

Electrical current detector

Abstract: A folded annular core of uniform cross section has an excitation winding and a feedback winding on each core half. A source of unidirectional current pulses periodically energizes the excitation windings to saturate the core. A measuring circuit detects the e.m.f. values induced in each excitation winding after each current pulse terminates, subtracts one value from another and integrates the difference to provide an output signal proportional to the current being measured. A feedback circuit produces a current proportional to the output signals to energize the feedback windings for nulling the core flux due to the current being measured to insure that the device operates in the linear region of the hysteresis loop of the core. A clamp-on current detector uses two folded annular cores to completely encircle a conductor carrying the current to be measured.

Individual axle wheel slip control system

Abstract: An individual axle wheel slip control system for electric traction motor drives employing series type direct current traction motors is described. With this system an auxiliary source of direct current is connected to the series field winding of each individual traction motor in parallel with and in addition to the normal direct current excitation with the polarity of the auxiliary source of direct current being such that when added to the normal excitation direct current, results in a reduction of the armature current and consequently a reduction in the tractive effort of the traction motor. A field current sensor responsive only to the field current of the traction motor being controlled, is provided along with a phase control circuit which is responsive to the output of the field current sensor and to a reference signal source for establising a reference median value of field current. The phase control circuit in turn is coupled to and controls the output of the auxiliary source of direct current for increasing the auxiliary field current in response to the field current sensor detecting a sudden decrease in the field current of the traction motor below the reference median value such as which would be produced upon the occurrence of slippage. A rate of change responsive network is coupled to the field current sensor for detecting relatively rapid rates of change in the sensed field current such as would occur with a rapidly accelerating wheel slip. The rate of change network is coupled to and additionally controls the phase control circuit for further increasing the auxiliary field current supplied to the field winding of the traction motor upon the occurrence of rapidly accelerating wheel slip. A sensitivity modifying circuit is provided for decreasing the sensitivity of the rate of change network for increasing values of field current whereby for relatively low values of field current, relatively fast and large auxiliary field current corrections are provided, and for relatively large values of field current, the auxiliary field current correction is slower and of lower value. The wheel slip control system further includes an overload protection circuit that is coupled to and controls the wheel slip control circuit and that is responsive to a current transformer that senses the overall value of the auxiliary field current supplied to the traction motor. By this arrangement the level of auxiliary field current being supplied from the auxiliary direct current source is regulated to some predetermined maximum level upon the current transformer sensing an overcurrent condition.

Surge arrestor for high voltage electric power applications

Abstract: A surge arrestor for high voltage electric power applications comprises series-coupled uncontrolled discharge devices each of which is shunted through resistors by a string of avalanche diodes connected in series opposition, and a capacitor. Connected in series with each uncontrolled discharge device is a controlled discharge device with its igniter electrode coupled to the output of a control unit of the discharge device with the output of a current sensor connected to its input, the input of the current sensor being placed in series with one said string paralleled by the controlled discharge device. In electric apparatus rated for above 100 kV it is expedient to use a surge arrestor composed of a string of series-connected uncontrolled discharge devices and two controlled discharge devices.

Method for measuring parameters of complex electric circuit components and device for effecting same

Abstract: A method, according to the invention, is effected by the application of a constant voltage directly across an input of a complex electric circuit, whose components are connected in parallel, and converting parameters of electric signals derived from an output of a measuring electric circuit, including the complex electric circuit, into time intervals. For this purpose, the current flowing through the components of a complex electric circuit is summed up with the linearly changing or constant reference current of the opposite direction, and a calibrated time interval is read off from the moment the total current or the integral of the total current attain a preset value. As the calibrated time interval elapses, the alteration of the linearly changing reference current is discontinued or the constant reference current is cut off. Then, as the total current or the integral of the current flowing through the components of the complex electric circuit attain a preset value, the constant voltage is cut off and the time interval is measured between the moment of reading off the calibrated time interval and that of cutting off constant voltage. Then the current obtained after the constant voltage is cut off is summed up with other linearly changing reference current or with other constant reference current and the time interval is measured between the moment the constant voltage is cut off and the moment the total current or the integral of the total current attain a preset value, the values of time intervals obtained being used for determining parameters of complex electric circuit components.

Waveform generator producing output current variations as a function of predetermined input and control signal values

Abstract: By deriving a substantially linear voltage signal from a pressure transducer and using that signal to control a plurality of current sources and current sinks, the controlled current may be passed through a resistance of known value to produce a usable output signal having a nonlinear relationship with respect to the pressure sensed by the transducer. If current sources to be controlled are designated by N, the resultant curve can have N-1 break points where the slope of the curve of output voltage with respect to sensed pressure changes.