Current sensor for phase inversion-modulation of AC signals
AssigneeGeneral Electric Company
InventorMiran Milkovic
Life of this patent
Estimating the term…
Abstract
A circuit for sensing the magnitude of an AC signal applied to the circuit includes control means for reversing the polarity of the AC signal to thereby generate an output signal which is proportional in amplitude to the magnitude of the AC signal and which has a phase, with respect to the phase of the AC signal, determined by the control means. The control means also provides the capability of generating output pulses from the circuit which have an amplitude proportional to the magnitude of the AC signal and a pulse-width-spacing proportional to the duty cycle of a pulsating control signal applied to the control means.
Claims14
In combination:
- (a) a low impedance current transformer having primary and secondary windings adapted for conducting primary and secondary currents respectively;
- (b) a very low input impedance operational amplifier having first and second input terminals and an output terminal;
- and
- (c) a switch, having substantially zero resistance, interconnecting the secondary winding of said current transformer with the first and second input terminals of said operational amplifier for switching the polarity of the secondary current of said current transformer between the first and second input terminals of said operational amplifier while providing a very low impedance connected across the secondary winding, resulting in a negligible potential across the first and second input terminals of said operational amplifier, and providing an output voltage from the output terminal of said operational amplifier having an amplitude proportional to the magnitude of the primary current of said current transformer and having a phase, with respect to the phase of the primary current, determined by the polarity of the current applied to the first and second input terminals of said operational amplifier by said switch.
The combination comprising:
- (a) a current transformer having primary and secondary windings adapted for conducting primary and secondary current respectively;
- (b) first, second and third operational amplifiers, each having first and second input terminals and an output terminal, the first input terminal of said first and second operational amplifiers being connected at opposite ends of the secondary winding of said current transformer with the second input terminal of said first, second and third operational amplifiers being connected in common to a source of potential;
- and
- (c) a switch connected across the secondary winding of said current transformer and being in communication with the output terminals of said first and second operational amplifiers and the first input terminal of said third operational amplifier for switching the polarity of the current from the secondary winding to the first input terminal of said third operational amplifier while alternately connecting the output terminals of said first and second operational amplifiers in feedback configuration to their respective first input terminals to maintain the potential across the secondary winding at substantially zero volts and thereby create a virtually short circuit operating condition for said current transformer while generating an output voltage at the output terminal of said third operational amplifier proportional in amplitude to the magnitude of the current from said current transformer and which has a phase, with respect to the phase of the transformer current, determined by the polarity of the current applied to the first input terminal of said third operational amplifier from said switch.
Dependencies are inferred from the claim text.