Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
1998-09-18
2001-06-26
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S251000, C327S511000, C335S018000, C361S187000
Reexamination Certificate
active
06252389
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a current detector for detecting a current in a main circuit of a power switching apparatus and to a power switching apparatus having the function of protecting an apparatus or a device under a load due to an overcurrent.
2. Description of the Related Art
A power switching apparatus is used to open or close an electric path between a single- or three-phase power source and an apparatus or a device under a load as a fixed contact and a movable contact are made to open or close by driving an iron core and the movable contact leading thereto by energization of an electromagnetic coil.
FIG. 9
is a partially sectional view of a conventional power switching apparatus shown in Japanese Patent No. 1,751,690, and
FIG. 10
is a partially sectional front view of the power switching apparatus.
In
FIG. 9
, a base
1
and a mounting base
2
, which are formed of an insulating material, constitute a casing for fixing and holding internal component parts. An operating-coil driving circuit board
6
has a circuit for converting a signal supplied from an external power source to a coil driving signal. An operating coil
5
drives an iron core through a magnetic field generated by the coil driving signal. A fixed core
4
and a movable core
3
form magnetic paths for the magnetic field generated by the operating coil
5
, and the movable core
3
is attracted to the fixed core
4
by the electromagnetic force acting in the gap between the fixed core
4
and the movable core
3
.
A movable contact
9
, which is connected to the movable core
3
, comes into contact with a fixed contact
8
through the action of the movable core
3
. As a result, a fixed contact point
11
and a movable contact point
12
attached to the contacts come into contact with each other, thereby making the electric path.
When the operating-coil driving signal is off, the driving force of the operating coil
5
is not present, and the movable core
3
and the fixed core
4
are separated by the force of a tripping spring
7
, so that the fixed contact point
11
and the movable contact point
12
are separated, thereby breaking the electric path.
Incidentally, a terminal screw
10
connects an electric wire from an external circuit to the fixed contact
8
.
FIG. 11
shows the structure of a conventional current transformer type current detector, and
FIG. 12
shows the structure of a conventional Hall-effect type current detector.
In the drawings, a conducting portion
13
and a terminal screw
14
are for allowing the current sensor to be energized by the current of the apparatus or device under the load, a current transformer
15
is for detecting the current at the conducting portion
13
, and an output line
16
outputs the current from a secondary winding of the current transformer
15
.
A magnetic core
17
is formed of a magnetic material disposed around the conducting portion
13
, and allows the magnetic flux generated by the current flowing across the conducting portion
13
to flow therethrough. The magnetic field is detected by a Hall-effect device
18
, and is outputted as a current signal.
With the conventional current detectors, the current is detected by the through type current transformer or by the magnetic core having a gap and the Hall-effect sensor disposed in the gap. In either method, it is necessary to form the closed loop in which the core of the current transformer or the magnetic core serving as a passage for the magnetic flux is disposed around the conducting portion. As a result, the magnetic core becomes larger than the current sensor, so that the current detector is difficult to be built into a power switching apparatus.
In addition, since it is necessary to provide the magnetic core around the conductive portion, it is necessary to use a small-diameter conducting portion and pass it through the magnetic core during the assembly into a product. Hence, there is a problem in that after the terminal screw is fitted, the conducting portion cannot be built into the product.
Furthermore, in an area where the working current is large, the conducting portion becomes large, so that the magnetic core is also bound to be large in shape. Additionally, it is necessary to make the sectional area of the magnetic core large to prevent the magnetic saturation in the large current area, with the result that the magnetic core tends to become large, and higher cost of the current sensor portion is entailed.
In addition, the conventional current detector is difficult to be built into the power switching apparatus, and it has been difficult for the power switching apparatus to be provided with the functions of protecting the apparatus or device under the load, monitoring the operation of the apparatus or device under the load, and detecting a fault of the power switching apparatus.
SUMMARY OF THE INVENTION
The present invention has been devised to overcome the above-described problems, and its object is to obtain a compact current detector in which a current detection circuit is made compact and a power switching apparatus provided with the functions of protecting an apparatus or a device under a load, monitoring the operation of the apparatus or device under the load, and detecting a fault of the power switching apparatus.
In order to solve the above object, according to the present invention, there is provided a current detector comprising: a Hall-effect sensor for detecting a magnetic field generated by a current flowing across a conducting portion; a magnetic core having a first end face for concentrating a magnetic flux and a second end face having a smaller area than the first end face, only the second end face being disposed at a position in close proximity to or in abutment against a magnetic field detecting surface of the Hall-effect sensor; and a signal processing circuit for processing an output signal from the Hall-effect sensor into a signal representing the current flowing across the conducting portion.
In addition, there are provided a pair of magnetic cores having their second end faces respectively disposed at the positions in close proximity to or in abutment against magnetic field detecting surfaces of the Hall-effect sensor on both sides thereof.
In addition, a flat plate-shaped magnetic core whose longitudinal direction is set in an energizing direction of the conducting portion, whose sectional area changes toward a position of the magnetic field detecting surface of the Hall-effect sensor, and which is arranged along a configuration of a surface of the conducting portion is disposed in close proximity to or in abutment against the conducting portion.
In addition, there are provided a pair of magnetic cores having their second end faces respectively disposed at the positions close to or contacting magnetic field detecting surfaces of the Hall-effect sensor on both sides thereof, and a distance between two mutually opposing surfaces of the pair of magnetic cores is arranged to be smaller than their spaced-apart dimension with respect to another magnetic member disposed in close proximity to the pair of magnetic cores.
In addition, a U-shaped conducting portion is provided, and the magnetic core and the Hall-effect sensor are provided on an inner surface of a U-shaped portion of the U-shaped conducting portion.
In addition, the magnetic core is disposed on three surfaces of a flat-shaped conductor.
In addition, in accordance with the present invention, there is provided a power switching apparatus having a current detector, characterized in that an output signal of a Hall-effect sensor passed through a temperature compensating circuit is set as a first output signal, the first output signal is processed into a current signal as a second output signal which is not subjected to temperature compensation, the first and second output signals are subjected to subtraction processing, and an output signal of a result of the processing is set as a signal proportional to a temperature of a terminal, so as to detec
Baba Sadaaki
Inoue Satoru
Mitsubishi Denki & Kabushiki Kaisha
Strecker Gerard R.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Current detector having magnetic core for concentrating a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Current detector having magnetic core for concentrating a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Current detector having magnetic core for concentrating a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2467186