JPH10241976A - Ac current detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the number of parts in a circuit and reduce the circuit scale by comprising a noise filter and a current transformation means wherein, with the noise filter coil as primary side, the primary current is transformed with a secondary coil for detecting a current value. SOLUTION: A coil L1 is inserted into one power source line between an AC power source and a rectification bridge 20, while a coil L2 is inserted into the other power source line between the AC power source and the rectification bridge 20. The coils L1 and L2 are wound oppositely in phase, forming a line coil 10a together with a core, as a whole. Here, relating to the line coil 10a, the coils L1 and L2 are wound for different turns. And the current flowing a primary side line coil 10a is transformed with a secondary side coil L3. Thus, the line coil 10a and the coil L3 constitute a current transformation means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an AC current detecting device for detecting a current value of an AC power supply.

[0002]

2. Description of the Related Art Conventionally, an inverter air conditioner utilizing this type of AC current detecting device is shown in FIG. The AC power supply uses a commercial power supply, and is connected to the rectifying bridge 2 via the line coil 1.
The output of the rectifying bridge 2 is smoothed and connected to the compressor driving DC motor 3. Of course, the line coil 1 operates as a noise filter, and is configured by winding two windings in opposite phases around a core (not shown). On the other hand, a line coil 1 and a rectifying bridge 2 for controlling the load of the DC motor 3 for driving the compressor.
And a current detection transformer 4 interposed therebetween, and the inverter control circuit 5 controls the output of the DC motor 3 for driving the compressor based on the output of the current detection transformer 4.

[0003]

In the case of the above-described conventional AC current detecting apparatus, a line coil is used together with the current detecting transformer, and two parts are provided, which requires an assembling space and increases the number of parts. There was a problem to do.

[0004] The present invention has been made in view of the above problems, and has as its object to provide an AC current detection device capable of reducing the number of components in a circuit and reducing the circuit scale.

[0005]

In order to achieve the above object, the invention according to claim 1 comprises a noise filter for reducing noise on a power supply line by a winding inserted in one line or each line of an AC power supply line. In addition, the noise filter has a winding on the primary side and a current transformer for detecting a current value by transforming a primary current in the winding on the secondary side.

[0006] In the invention according to claim 1 configured as described above, the noise filter reduces noise on the power supply line by a wire inserted into one line or each line of the AC power supply line. . The winding may be any winding that is connected in series with at least the power supply to reduce noise on the power supply line. Therefore, it can be constituted by an LC circuit or the like composed of a winding and a capacitor inserted into the power supply line.

Of course, the winding characteristics and the material of the winding are not particularly limited.
Since a current always flows from a power supply in many cases, it is more advantageous to use a winding made of a material having low heat generation due to resistance and high dielectric strength. On the other hand, the current transformer means
While the winding of the noise filter is used as a primary side, a primary current is transformed by a secondary side winding to detect a current value. That is, if an alternating current flows through the primary winding, an exciting current flows by forming a closed circuit in the secondary winding, and the primary current is measured by measuring the exciting current value on the secondary side. Estimate the value.

According to a second aspect of the present invention, there is provided a first winding inserted in a stage preceding a load connected to an AC power supply,
A line coil comprising a second winding having a number of turns different from the number of turns of the first winding and inserted into the latter stage of the load so as to have a phase relationship opposite to that of the first winding. And a current transformer for detecting the current value by transforming the primary current with the third winding on the secondary side while using the line coil as the primary side.

[0010] In the invention according to claim 2 configured as described above, the line coil is inserted into the first winding inserted before the load connected to the AC power supply, and inserted into the second winding after the load. And a second winding. Further, the first winding and the second winding have different numbers of turns, and the currents flowing through both windings are in opposite phase relation to each other. For this reason, the magnetic field generated in the first winding and the magnetic field generated in the second winding are opposite to each other, and a certain amount of the magnetic field is canceled out. A corresponding magnetic field will be generated. The line coil having such a configuration is particularly effective as a noise reduction circuit in an AC power supply line, and more specifically, has a function of blocking common mode noise conducted between the power supply line and the ground.

On the other hand, the current transformer detects the current value by transforming the primary current in the third winding on the secondary side with the line coil as the primary side. That is, as described above, since the first winding and the second winding have different numbers of turns, a magnetic field is generated as a whole line coil, and an exciting current is generated on the secondary side using this magnetic field. Is occurring. Here, if the first winding and the second winding have the same number of turns, the magnetic fields generated by the two windings are completely cancelled, and the line coil does not generate a magnetic field as a whole. In such a state, an exciting current cannot be generated on the secondary side, and in this sense, the first winding and the second winding have different numbers of turns.

In the above-described current transformer, if the core is magnetically saturated within the allowable range of the current flowing through the circuit, the magnetic flux density does not change with time even if the primary current increases. In such a case, even if the primary current increases, the secondary current does not change with time, and the primary current may not be correctly estimated. Therefore, an AC current detection device according to a third aspect of the present invention is the AC current detection device according to any one of the first and second aspects, wherein the core around which each winding is wound does not generate magnetic saturation. Is the gist.

To avoid magnetic saturation,
The iron core may be formed by laminating silicon steel sheets, or a core of a powder magnetic material having a high saturation magnetic flux density and a gentle magnetic saturation characteristic may be used, or the first and second windings may be used. May be reduced as a whole, or both may be used in combination, and may be appropriately changed. Also,
Ferrite or the like may be used from the viewpoint of a filter for reducing high frequency components.

[0013]

As described above, according to the present invention, the number of components in a circuit can be reduced and the circuit scale can be reduced by integrating a noise filter winding and a current detection transformer. An AC current detection device can be provided. According to the second aspect of the present invention, the circuit scale can be further reduced by integrating the line coil and the current detection transformer. Furthermore, according to the third aspect of the present invention, since the magnetic saturation of the core is not generated, the accuracy of current detection can be improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an inverter air conditioner using an AC current detection device according to an embodiment of the present invention. In the figure, a commercial AC power source is connected to a rectifying bridge 20 via an AC current detecting device 10, and the output of the rectifying bridge 20 is smoothed and connected to a compressor driving DC motor 30.

The AC current detecting device 10 comprises a core 11 made of a so-called CI-shaped ferrite shown in FIG. 2, and three windings L1 to L3 wound around the core 11. That is, as shown in FIG. 3, the windings L1 to L3 are wound around the core 11. The winding order is not particularly limited, and may be the order of the winding L1, the winding L2, and the winding L3, or the winding L1, the winding L3, and the winding L3.
The order of the winding L2 may be used, or the winding L3, the winding L
1, the order of the winding L2. Of course, core 11
Is not particularly limited, and may be an EI shape or a ring shape.

Of these windings L1 to L3, winding L1
Is inserted into one power supply line between the AC power supply and the rectifying bridge 20, and the winding L2 is inserted into the other power supply line between the AC power supply and the rectifying bridge 20.
Further, the winding L1 and the winding L2 are wound so as to have an opposite phase relationship to each other, and form a line coil 10a as a whole together with the core 11 to reduce noise from the AC power supply. Plays a role. Here, since the core 11 is made of ferrite, noise of high frequency components can be reduced efficiently.

In this embodiment, the core 11 having the shape shown in FIG. 2 is used. However, the shape is not necessarily limited to this shape. . Therefore, each of the windings L1 to L
As long as the magnetic flux is induced at the center of 3, the iron core of various shapes may be used, or it may be formed of a dust magnetic material or the like. In the present embodiment, the winding L
1, L2 and L3 are adjacent to each other, but may be overlapped as long as the magnetic flux is induced by the core 11 as described above.

In general, the line coil for the noise filter may have the same number of turns between the two windings.
, The winding L1 and the winding L2 are wound so as to have different numbers of turns. As a result, the magnetic field generated by the winding L1 and the magnetic field generated by the winding L2, which are in opposite phases, are partially cancelled. However, if the number of turns is different, the core 11 A magnetic field is generated inside.

Of course, even when the magnetic field is generated by changing the number of turns, the magnetic saturation of the core 11 is set to such an extent that the magnetic saturation does not occur. As will be described later in detail, since the exciting current based on the change in the magnetic field of the line coil 10a is generated in the winding L3, an accurate current value cannot be detected when the core 11 reaches magnetic saturation. Therefore, in the present embodiment, the core 11 is formed of ferrite so that the saturation magnetic flux density is high and the magnetic saturation characteristics are moderate, and the core number difference between the windings L1 and L2 is adjusted in advance. 1
No. 1 magnetic saturation is prevented.

On the other hand, an inverter control circuit 40 for controlling the output of the DC motor 30 for driving the compressor is connected to the winding L3, and a closed circuit is formed as a whole on the winding L3 side. Therefore, as described above, the line coil 10a
, A magnetic field is generated, and an exciting current is generated on the winding L3 side. This exciting current is proportional to the current flowing through the line coil 10a as long as the turns ratio of each winding is constant.
Approximate the current flowing on the a side. That is, the current flowing through the primary side line coil 10a is transformed by the secondary side winding L3. In this sense, the line coil and the winding L
3 constitutes the current changing means.

The inverter control circuit 40 has a winding L
A current detection resistor connected in series to the power supply 3 is detected, a current value is detected by the current detection resistor, and the output of the compressor driving DC motor 30 is controlled based on the detection result. . Further, in the present embodiment, the AC current detection device is applied to an inverter air conditioner. However, it is needless to say that any device using an AC power supply can be applied to various AC current detections such as home appliances. No.

Next, the operation of this embodiment will be described.
The commercial AC power supply is connected to the rectifying bridge 20 via the AC current detecting device 10 and smoothes the output of the rectifying bridge 20 to make the DC motor 3
Connected to 0. As a result, a DC current always flows through such a circuit, and the DC motor 30 for driving the compressor operates. The AC current detection device 10 includes a core 11 and windings L1 to L3 wound around the core 11, and a winding L1 inserted into one power supply line between the AC power supply and the rectifying bridge 20. And a winding L2 inserted into the other power supply line between the AC power supply and the rectifying bridge 20 in a reverse phase relationship with the winding L1 to reduce noise on the power supply line. doing. Further, since the winding numbers of the winding L1 and the winding L2 are different from each other, the mutual magnetic fields are somewhat offset, but a magnetic field corresponding to the difference in the number of windings is generated in the entire line coil 10a. .

On the other hand, the winding L3 has an inverter control circuit 4
0 are connected to form a closed circuit as a whole. When a magnetic field is generated in the line coil 10a as described above, an exciting current flows. As is well known, as long as the number of turns of each winding is constant, the exciting current generated in the winding L3
It is proportional to the value of the current flowing on the a side. Therefore, the exciting current is measured by a current detecting resistor connected in series to the winding L3 in the inverter control circuit 40, and the output of the compressor driving DC motor 30 is controlled based on the measured current value.

FIG. 4A is a waveform diagram showing the time change of the detection current of the inverter control circuit 40 when the power consumption of the DC motor 30 for driving the compressor is a reference state using the AC 100 V power supply in the circuit having the above configuration. FIG. 4B is a waveform diagram showing a temporal change of a detection current of the inverter control circuit 40 when the power consumption is about 1.5 times the reference time. As is clear from the figure, the current value proportional to the output in each case can be detected.
The inverter control circuit 40 controls the output of the compressor driving DC motor 30 so that the current value becomes constant.

As described above, the line coil composed of the windings L1 and L2 inserted into the AC power supply line reduces noise on the power supply line, and connects the windings L1 and L2 having different windings to the primary side. And the secondary winding L3
Since the primary current is transformed to detect the current value, it is possible to provide an AC current detection device capable of reducing the number of components in the circuit and reducing the circuit scale.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an inverter air conditioner using an AC current detection device according to an embodiment.

FIG. 2 is a front view of a core.

FIG. 3 is a front view of a core in a state where a winding is wound.

FIG. 4 is a waveform diagram showing a time change of a detection current of the inverter control circuit.

FIG. 5 is a circuit diagram of an inverter air conditioner using a conventional AC current detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... AC current detection apparatus 10a ... Line coil 11 ... Core L1, L2, L3 ... Winding

Claims (3)

[Claims] 1. A noise filter for reducing noise on a power supply line by a winding inserted into one or each line of an AC power supply line, a winding of the noise filter being used as a primary winding and a secondary winding. And a current transformer for detecting a current value by transforming the primary current. 2. A first winding inserted before a load connected to an AC power supply, and a first winding inserted after the load so as to have an antiphase relationship with the first winding. And a line coil composed of a second winding having a different number of turns from the first winding, and a primary current flowing through the third winding on the secondary side while using this line coil as a primary side. And a current transformer for detecting a current value by transforming the current. 3. The AC current detecting device according to claim 1, wherein the core around which each winding is wound does not generate magnetic saturation. .