US 2009/0021237 A1Published application

Current transformer and electric energy meter

AssigneeMetglas, Inc.

InventorShin Nakajima

Life of this patent

Estimating the term…

Abstract

A current transformer detects a sine-wave alternating current having a maximum effective current value Imax(Arms) and a frequency f(Hz) and a half-sine-wave rectified current having a maximum peak value Ipeak(Aop) and a frequency f(Hz) in a primary winding, consisting of at least one magnetic core with one turn of primary winding and at least one multiple turns of secondary winding to which a detecting resistor is connected.

Claims6

Dependent claims

A current transformer to detect a sine-wave alternating current having a maximum effective current value Imax(Arms) and a frequency f(Hz), and a half-sine-wave rectified current having a maximum peak value Ipeak(Aop) and a frequency f(Hz) in a primary winding, comprising:

at least one magnetic core having one turn of primary winding and multiple turns of secondary winding to which a detecting resistor is connected in parallel, and having an effective cross section Ae of the magnetic core being determined by
A
e
≥
A
e

(
min
)
*


(
m
2
)
A
e

(
min
)
*
=
I
max
·
(
R
Cu
+
R
b
)
4.44
·
f
·
N
s
2
·
B
s


(
m
2
)
,
where
Bs is a saturation magnetic flux density of the magnetic core (T),
Ns is a number of turns of the secondary winding,
RCu is a resistance of the secondary winding (Ω),
Rb is a resistance of the detecting resistor (Ω), and
A
e
≥
A
e

(
min
)
**


(
m
2
)
A
e

(
min
)
**
=
(
R
Cu
+
R
b
)

(
D
i

(
min
)
+
1.5
×
10
-
3
)
2


f


μ
r

μ
0

N
s
2

tan


φ


(
m
2
)
D
i

(
min
)
=
a

I
max
+
b


(
m
)
0.75
×
10
-
3
≤
a
≤
1.25
×
10
-
3


(
m

/

A
0.5
)
8.0
×
10
-
3
≤
b
≤
12.0
×
10
-
3


(
m
)
,
where
Di(min) is a minimum value of an inner diameter of the magnetic core (m),
μr is an incremental relative permeability of the magnetic core,
μ0 is a permeability of a vacuum, 4π×10−7 (H/m), and
φ is a phase error of current transformer (rad),
and the mean magnetic path length le satisfies

l
e
≥
l
e

(
min
)
*


(
m
)
l
e

(
min
)
*
=
I
peak
π

〈
H
s
-
N
p
·
I
peak

(
R
Cu
+
R
b
)
2


π


μ
r

μ
0

N
s
2
·
A
e

{
T
2

[
cos

(
2


π


T
Vs


0
T
)
-
cos

(
2


π

[
(
T
/
2
)
-
T
Vs


0
]
T
)
]
+
2

T
Vs


0
-
(
T
/
2
)
}
〉


(
m
)



H
s
=
Bs
μ
r

μ
0


(
A

/

m
)



T
Vs


0
=
T
2


π

sin
-
1

(
1
π
)


(
s
)
,
where



T
=
1

/

f

:


period


(
s
)
,


and

l
e
≥
l
e

(
min
)
**


(
m
)



l
e

(
min
)
**
=
π

(
D
i

(
min
)
+
1.5
×
10
-
3
)


(
m
)
.

447 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/222,667Filed 13 Aug 2008
Priority: 9 Nov 2005
Published: 22 Jan 2009
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G01R 15/183
Using inductive devices, e.g. transformers: using transformers with a magnetic core
H01F 38/30
Current transformers: constructions
H01F 27/24
Details of transformers or inductances, in general: magnetic cores
H01F 27/34
Details of transformers or inductances, in general: special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load…

Family

Application60/734,789Us provisional application · filed 9 Nov 2005
Application12/222,667Continuation
US 7,656,149 B2Related patent
US 2009/0021237 A1This patent

From the US filing history. Foreign family members aren’t listed.

Timeline

Citations

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Abstract

at least one magnetic core having one turn of primary winding and multiple turns of secondary winding to which a detecting resistor is connected in parallel, and having an effective cross section Ae of the magnetic core being determined by
A
e
≥
A
e

(
min
)
*


(
m
2
)
A
e

(
min
)
*
=
I
max
·
(
R
Cu
+
R
b
)
4.44
·
f
·
N
s
2
·
B
s


(
m
2
)
,
where
Bs is a saturation magnetic flux density of the magnetic core (T),
Ns is a number of turns of the secondary winding,
RCu is a resistance of the secondary winding (Ω),
Rb is a resistance of the detecting resistor (Ω), and
A
e
≥
A
e

(
min
)
**


(
m
2
)
A
e

(
min
)
**
=
(
R
Cu
+
R
b
)

(
D
i

(
min
)
+
1.5
×
10
-
3
)
2


f


μ
r

μ
0

N
s
2

tan


φ


(
m
2
)
D
i

(
min
)
=
a

I
max
+
b


(
m
)
0.75
×
10
-
3
≤
a
≤
1.25
×
10
-
3


(
m

/

A
0.5
)
8.0
×
10
-
3
≤
b
≤
12.0
×
10
-
3


(
m
)
,
where
Di(min) is a minimum value of an inner diameter of the magnetic core (m),
μr is an incremental relative permeability of the magnetic core,
μ0 is a permeability of a vacuum, 4π×10−7 (H/m), and
φ is a phase error of current transformer (rad),
and the mean magnetic path length le satisfies

l
e
≥
l
e

(
min
)
*


(
m
)
l
e

(
min
)
*
=
I
peak
π

〈
H
s
-
N
p
·
I
peak

(
R
Cu
+
R
b
)
2


π


μ
r

μ
0

N
s
2
·
A
e

{
T
2

[
cos

(
2


π


T
Vs


0
T
)
-
cos

(
2


π

[
(
T
/
2
)
-
T
Vs


0
]
T
)
]
+
2

T
Vs


0
-
(
T
/
2
)
}
〉


(
m
)



H
s
=
Bs
μ
r

μ
0


(
A

/

m
)



T
Vs


0
=
T
2


π

sin
-
1

(
1
π
)


(
s
)
,
where



T
=
1

/

f

:


period


(
s
)
,


and

l
e
≥
l
e

(
min
)
**


(
m
)



l
e

(
min
)
**
=
π

(
D
i

(
min
)
+
1.5
×
10
-
3
)


(
m
)
.

447 more elements

Facts

Application

12/222,667Filed 13 Aug 2008

Priority

9 Nov 2005

Published

22 Jan 2009

Term ends

Not estimatedThe source records don’t support an estimate.

Classification6 codes

G01R 15/183
Using inductive devices, e.g. transformers: using transformers with a magnetic core
H01F 38/30
Current transformers: constructions
H01F 27/24
Details of transformers or inductances, in general: magnetic cores
H01F 27/34
Details of transformers or inductances, in general: special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load…