Current sensing circuit and current sensing assembly including the same

Patent metadata

Field	Value
Publication number	US-10388445-B2
Application number	US-201615386063-A
Country	US
Kind code	B2
Filing date	Dec 21, 2016
Priority date	Dec 21, 2016
Publication date	Aug 20, 2019
Grant date	Aug 20, 2019

Abstract

A current sensing circuit for use with a Rogowski coil arranged around a conductor having a primary current includes input terminals structured to receive an output voltage of the Rogowski coil, an analog to digital converter structured to convert a differential voltage to a digital differential voltage signal, a digital integrator structured to receive the digital differential voltage signal, to implement a discrete-time transfer function that is a transform of a transfer function of an analog integrator, and to output a digital integrator output signal, and a direct current blocker filter structured to remove a direct current bias from the digital integrator output signal and to output a digital current output signal that is proportional to the primary current in the conductor.

First claim

What is claimed is:

1. A current sensing circuit for use with a Rogowski coil arranged around a conductor having a primary current, the current sensing circuit comprising:
input terminals structured to receive an output voltage of the Rogowski coil;
filtering elements structured to filter high frequency voltage from the output voltage and to output a filtered output voltage;
an amplifier structured to receive the filtered output voltage and produce a differential voltage;
an analog to digital converter structured to convert the differential voltage to a digital differential voltage signal;
a digital integrator structured to receive the digital differential voltage signal, to implement a discrete-time transfer function that is a transform of a transfer function of an analog integrator, and to output a digital integrator output signal;
a direct current blocker filter structured to remove a direct current bias from the digital integrator output signal and to output a digital current output signal that is proportional to the primary current in the conductor, and
wherein the discrete-time transform implemented by the digital integrator is an impulse-invariant transform of the transfer function of the analog integrator, and
wherein the analog integrator is an RC-filter having a resistance of R and a capacitance of C; and wherein the discrete-time transfer function of the digital integrator is defined by the following equation:

H
⁡

(
z
)

=

y
⁡

(
z
)

x
⁡

(
z
)

=

α
·

T
S

1
-

e

-
α

⁢

⁢

T
S

⁢

z

-
1

=

b
0

1
-

a
1

⁢

z

-
1

where T s is a sampling interval;

α
=

1
RC

;

a
1

=

e

-
α

⁢

⁢

T
S

=

e

-

T
S

RC

;

b
0

=

α
·

T
S

;

 and z −1 denotes a one-sample delay.

2. The current sensing circuit of claim 1 , wherein the digital integrator has coefficients of a 1 and b 0 ; wherein a 1 is defined by the following equation:

a
1

=

cos
⁡

(

Δ
⁢

⁢

n
·

ω
e

)

cos
⁡

[

(

Δ
⁢

⁢
n

-
1

)

·

ω
e

]

wherein b 0 is defined by the following equation:
b 0 =√{square root over (1−2 a 1 cos ω e +a 1 2 )}

wherein Δn is a phase difference number of samples;

ω
e

=

2
⁢

Assignees

• Eaton Corp
• Eaton Intelligent Power Ltd

Inventors

• Gao Zhi
• Hosko Daniel A
• Miller Theodore J

Classifications

• H03H17/04

  Recursive filters · CPC title

• G01R15/181 Primary

  using coils without a magnetic core, e.g. Rogowski coils · CPC title

• H01F5/02 Primary

  wound on non-magnetic supports, e.g. formers · CPC title

• H01F38/20

  Instruments transformers · CPC title

• G01R19/2506

  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 title