Intelligent electronic device having circuitry for reducing the burden on current transformers
First Claim
1. A current sensor comprising:
- a transformer including a primary winding configured for sensing a current delivered to a load and a secondary winding configured for outputting a scaled current via first and second leads;
an amplification circuit configured for variably amplifying the scaled output current and maintaining the output of the secondary winding at near zero voltage, wherein the amplification circuit includes;
an operational amplifier having a negative input and a positive input, the negative input and positive input being directly and physically connected to the first and second leads of the secondary winding, respectively; and
a variable feedback resistance coupled across the negative input of the operational amplifier and an output of the operational amplifier for variably amplifying the scaled output current; and
at least one processor that generates a control signal for controlling the variable feedback resistance based on a predetermined threshold of the output of the operational amplifier.
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Accused Products
Abstract
An intelligent electronic device (IED), e.g., an electrical power meter, having circuitry for reducing the burden placed on at least one current sensor of the device resulting in a highly accurate measurement by the at least one current sensor is provided. The circuitry of the present disclosure reduces the burden on the current sensor while providing amplification, e.g., gain control, to the input signal. The circuitry includes at least one current sensor outputting a signal to an operational amplifier (op amp) having a controlled variable feedback resistance. By employing an operational amplifier in the circuitry, the output of the current sensor will be at a near zero volts condition at all times thus reducing the burden on the current sensor.
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Citations
17 Claims
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1. A current sensor comprising:
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a transformer including a primary winding configured for sensing a current delivered to a load and a secondary winding configured for outputting a scaled current via first and second leads; an amplification circuit configured for variably amplifying the scaled output current and maintaining the output of the secondary winding at near zero voltage, wherein the amplification circuit includes; an operational amplifier having a negative input and a positive input, the negative input and positive input being directly and physically connected to the first and second leads of the secondary winding, respectively; and a variable feedback resistance coupled across the negative input of the operational amplifier and an output of the operational amplifier for variably amplifying the scaled output current; and at least one processor that generates a control signal for controlling the variable feedback resistance based on a predetermined threshold of the output of the operational amplifier. - View Dependent Claims (2, 3, 4, 5, 7, 8)
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6. An intelligent electronic device comprising:
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a transformer including a primary winding configured for sensing a current delivered to a load and a secondary winding configured for outputting a scaled current via first and second leads; an amplification circuit configured for variably amplifying the scaled output current and maintaining the output of the secondary winding at near zero voltage, wherein the amplification circuit includes; an operational amplifier having a negative input and a positive input, the negative input and positive input being directly and physically connected to the first and second leads of the secondary winding, respectively; and a variable feedback resistance coupled across the negative input of the operational amplifier and an output of the operational amplifier for variably amplifying the scaled output current; at least one analog-to-digital converter configured for receiving an amplified output and converting the amplified output to a digital signal; and at least one processor configured to receive the digital signal and determine a value for the current delivered to the load and generates a control signal for controlling the variable feedback resistance based on a predetermined threshold of the output of the operational amplifier. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A self-contained current sensor comprising:
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a housing; a transformer disposed in the housing, the transformer including a primary winding configured for sensing a current delivered to a load and a secondary winding configured for outputting a scaled current via first and second leads; an amplification circuit disposed in the housing and configured for variably amplifying the scaled output current and maintaining the output of the secondary winding at near zero voltage, wherein the amplification circuit includes; an operational amplifier having a negative input and a positive input, the negative input and positive input being physically and directly connected to the first and second leads of the secondary winding, respectively; and a variable feedback resistance coupled across the negative input of the operational amplifier and an output of the operational amplifier for variably amplifying the scaled output current; and at least one processor disposed in the housing that generates a control signal for controlling the variable feedback resistance based on a predetermined threshold of the output of the operational amplifier. - View Dependent Claims (15, 16, 17)
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Specification