Compensating for the skin effect in a shunt

• US 10,447,243 B2
• Filed: 12/14/2017
• Issued: 10/15/2019
• Est. Priority Date: 12/14/2016
• Status: Active Grant

• Current Assignee: Sensata Technologies Incorporated (Sensata Technologies Holding Plc)
• Original Assignee: Sendyne Corp. (Sensata Technologies Holding Plc)
• Inventors: Tsividis, Yannis
• Primary Examiner(s): Shah, Kamini S
• Assistant Examiner(s): Khan, Iftekhar A
• Application Number:
  US15/766,369
• Publication Number:
  US 20180316335A1
• Time in Patent Office: 670 Days
• Field of Search: 703 2
• CPC Class Codes: G01R 19/0007 Frequency selective voltage or current level measuring measuring frequency G01R23/00; testing attenuation in line transmission systems H04B3/48; monitoring testing in transmission systems H04B17/00
• CPC Class Codes: G01R 19/2506 Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values G01R19/003 takes precedence; Details concerning sampling, digitizing or waveform capturing displaying waveforms G01R13/00; analog sampling G01R19/0053
• CPC Class Codes: G01R 23/165 using filters
• CPC Class Codes: G06F 17/10 Complex mathematical operations function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544
• CPC Class Codes: H03H 17/0202 Two or more dimensional filters; Filters for complex signals multidimensional convolutions G06F17/153
• CPC Class Codes: H03H 17/0219 Compensation of undesirable effects, e.g. quantisation noise, overflow stability problems H03H17/0461
• CPC Class Codes: H03H 17/04 Recursive filters
• CPC Class Codes: H03H 2017/021 Wave digital filters
• CPC Class Codes: H03H 7/06 including resistors H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence

Abstract

A method and apparatus to compensate for distortion of a waveform due to the skin effect in a current shunt. The method includes modeling the complex impedance of the shunt as component complex impedances. By designing a filter corresponding to the component complex impedances, the distortion of a waveform across the shunt may be reversed to provide an accurate replica of the undistorted waveform.

Claims

1. A method for use with a current shunt, the shunt having a complex impedance, wherein the complex impedance produces frequency-dependent effects upon a voltage waveform across the shunt when passing an electric current through the shunt, the method comprising:

modeling the complex impedance of the shunt as a summation of at least two component complex impedances associated with parallel paths through the shunt, thereby creating a shunt model;

designing a physical electronic filter corresponding to the shunt model to reverse the frequency-dependent effects of the complex impedance of the shunt on the voltage waveform;

physically connecting the filter to the shunt by an electrical connection, thereby applying the filter to the frequency-dependent voltage waveform, wherein the frequency-dependent voltage waveform is transformed into a linear function of the passing current; and

reading the transformed value of the passing current,

wherein the step of modeling the complex impedance of the shunt further comprises;

modeling the parallel paths through the shunt as a parallel connection of at least two branches, each branch comprising a series connection of an inductor having a value of inductance and a resistor having a value of resistance; and

assigning a numerical value to the value of inductance and a numerical value to the value of resistance for each branch of the shunt model.

2. The method of claim 1, wherein the physical electronic filter corresponding to the shunt model is an analog filter, and the step of designing a physical electronic filter further comprises

connecting a plurality of parallel-connected pairs of components in series, each parallel-connected pair of components comprising a compensating capacitor having a value of compensating capacitance and a compensating resistor having a value of compensating resistance.

3. The method of claim 2, wherein the step of designing a physical electronic filter further comprises calculating a value of compensating resistance in order to provide a specific value of conductance and a value of a compensating capacitance.

4. The method of claim 1, wherein the physical electronic filter corresponding to the shunt model further comprises a voltage-to-current converter.

5. The method of claim 1, wherein the physical electronic filter corresponding to the shunt model is a digital filter, and the step of designing a physical electronic filter further comprises:

defining a system transfer function of the digital filter as a summation of at least two component transfer functions, each associated with a component value of complex impedance;

defining the at least two component transfer functions as functions of a complex variable in the analog domain; and

converting the at least two transfer functions defined as functions of a complex variable in the analog domain into functions of a complex variable in the digital domain.

6. The method of claim 5, further comprising sampling the voltage waveform across the shunt over at least two sampling periods at a defined sampling rate, thereby producing sampled signal data.

7. The method of claim 6, wherein the step of applying the filter to the frequency-dependent voltage waveform further comprises:

providing the sampled signal data as values for use with the functions of a complex variable in the digital domain; and

solving the functions of a complex variable in the digital domain for the at least two component transfer functions for the defined sampling rate.

8. The method of claim 7, further comprising an antialiasing filter connected between the shunt and the filter, wherein the antialiasing filter rejects frequency components at very high frequencies.

9. The method of claim 5, wherein the digital filter is executed in a software program, and the step of designing a physical electronic filter further comprises implementing the software program in an embedded controller.