Switched-voltage control of the magnetization of current transforms and other magnetic bodies
First Claim
1. A method for controlling a magnetic flux in a magnetic body;
- said magnetic body being positioned relative to a conductive winding in such a way that a change of said magnetic flux is associated with an induced voltage across said winding;
said induced voltage being proportional to a rate of change of said magnetic flux;
said winding conducting an electric current;
said method comprising the control of a voltage device connected to said winding;
said voltage device producing an adjustable output voltage that controls said induced voltage, thereby controlling said rate of change of said magnetic flux;
said adjustable output voltage causing said induced voltage to have such waveform and magnitude so as to be approximately proportional to a preferred rate of change of said magnetic flux;
an instantaneous magnitude of said induced voltage differing from an instantaneous magnitude of said adjustable output voltage because of voltage drops associated with said electric current flowing through loop impedances;
said method utilizing a parameter related to said electric current and characteristics of said loop impedances to control said adjustable output voltage so as to compensate for said voltage drops, thereby optimizing said adjustable output voltage for optimal control of said magnetic flux;
wherein the improvement is in the control of said voltage device, said voltage device comprising an electric power supply means for providing one or more d-c voltage outputs, and an electronic switch means for periodically connecting said one or more d-c voltage outputs in series with said winding, said adjustable output voltage thereby being a pulsed voltage;
said method further controlling said electronic switch means so that an average value over time of said induced voltage is approximately proportional to said preferred rate of change of said magnetic flux, thereby effecting control of said magnetic flux;
whereby an energy efficiency of said method is improved.
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Abstract
The magnetic flux of a magnetic body is controlled with voltage pulses from an active voltage source. The voltage pulses are applied to a winding circuit which is magnetically coupled to the magnetic body. An electronic switch means is used to generate the voltage pulses from a d-c power supply. A control circuit receives information about the winding current, and utilizes known loop impedances to optimize the voltage pulses for optimal magnetic control. Utilizing voltage pulses rather than a continuously variable voltage source has the advantage of lower cost and improved energy efficiency for many applications. The invention may be utilized for measurement of a-c current and d-c current utilizing ordinary current transformers. The switched-voltage control that is disclosed also may be used to facilitate accurate measurement of a-c current in a self-powered manner, with the power supply for the electronics deriving its power from the current transformer secondary circuit.
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Citations
20 Claims
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1. A method for controlling a magnetic flux in a magnetic body;
- said magnetic body being positioned relative to a conductive winding in such a way that a change of said magnetic flux is associated with an induced voltage across said winding;
said induced voltage being proportional to a rate of change of said magnetic flux;
said winding conducting an electric current;
said method comprising the control of a voltage device connected to said winding;
said voltage device producing an adjustable output voltage that controls said induced voltage, thereby controlling said rate of change of said magnetic flux;
said adjustable output voltage causing said induced voltage to have such waveform and magnitude so as to be approximately proportional to a preferred rate of change of said magnetic flux;
an instantaneous magnitude of said induced voltage differing from an instantaneous magnitude of said adjustable output voltage because of voltage drops associated with said electric current flowing through loop impedances;
said method utilizing a parameter related to said electric current and characteristics of said loop impedances to control said adjustable output voltage so as to compensate for said voltage drops, thereby optimizing said adjustable output voltage for optimal control of said magnetic flux;wherein the improvement is in the control of said voltage device, said voltage device comprising an electric power supply means for providing one or more d-c voltage outputs, and an electronic switch means for periodically connecting said one or more d-c voltage outputs in series with said winding, said adjustable output voltage thereby being a pulsed voltage;
said method further controlling said electronic switch means so that an average value over time of said induced voltage is approximately proportional to said preferred rate of change of said magnetic flux, thereby effecting control of said magnetic flux;
whereby an energy efficiency of said method is improved. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- said magnetic body being positioned relative to a conductive winding in such a way that a change of said magnetic flux is associated with an induced voltage across said winding;
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8. Apparatus for controlling a magnetic flux in a magnetic body;
- a winding being positioned relative to said magnetic body in such a way that a rate of change of said magnetic flux is proportional to an induced voltage across said winding, said winding comprising one or more turns of conductive material;
said apparatus comprising(a) a current-sensing means for providing an information signal containing information about an electric current flowing in said winding; (b) a controllable voltage device connected to said winding, said voltage device producing an adjustable output voltage which controls said induced voltage and thereby controls said rate of change of said magnetic flux; and (c) a suitable control means for receiving said information signal and controlling said voltage device;
said control means utilizing said information signal and characteristics of loop impedances through which said electric current flows to optimize said adjustable output voltage for optimal control of said magnetic flux;wherein the improvement is that said controllable voltage device comprises an electric power supply means for providing one or more d-c voltage outputs, and an electronic switch means for periodically connecting said one or more d-c voltage outputs in series with said electric current, said adjustable output voltage thereby being a pulsed voltage;
whereby an energy efficiency of said apparatus is improved. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
- a winding being positioned relative to said magnetic body in such a way that a rate of change of said magnetic flux is proportional to an induced voltage across said winding, said winding comprising one or more turns of conductive material;
Specification