JPH0897060A - Higher harmonic electric current restraining device - Google Patents

Abstract

PURPOSE: To enhance a higher harmonic electric current restraining device in restraining capacity by a method wherein two coils connected in parallel between a load and a power supply are provided winding around the same toroidal main magnetic circuit in the same direction, and a toroidal bypass magnetic circuit smaller than the main magnetic circuit in amount of saturation magnetic flux is formed penetrating through the coils respectively, wherein a bypass magnetic flux is oriented circulating outwards from inside the coil. CONSTITUTION: A higher harmonic current restraining device 1 is interposed between a load L and a power supply S. The higher harmonic current restraining device 1 is composed of two coils which are connected in parallel and wound around the lateral sides of the same rectangular toroidal main iron core 3 in the same direction. A bypass iron core 4 is set smaller than the toroidal main iron core 3 in amount of saturation magnetic flux. A toroidal main magnetic circuit is formed of the toroidal main iron core 3, and toroidal bypass magnetic circuits 5 are composed of the toroidal main iron core 3 and the bypass iron core 4 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current suppressor for suppressing the influence of harmonic current.

[0002]

2. Description of the Related Art Recently, accidents such as explosion, burnout, and power failure of capacitor equipment, which are considered to be caused by harmonic interference, have frequently occurred in urban areas. These harmonics are generated by semiconductors such as rectifiers and thyristors built into industrial equipment and household appliances, and these harmonic currents are generated by generators via transmission and distribution lines. It is a source of the above-mentioned various accidents due to the fact that the current flows back to (1) and the voltage drop distorts the distribution voltage, and the harmonic component becomes a noise component and affects the equipment. The 5th harmonic and the 7th harmonic are particularly problematic at this time.

FIG. 8 shows the waveform distortion due to this harmonic, and it can be seen that the fundamental waveform component A and the harmonic component B are combined to form a distorted waveform C.

As a countermeasure against this, in a phase advancing capacitor, a measure is taken to increase the reactance of the series reactor used in the capacitor to suppress the inflow amount of the fifth harmonic.

[0005]

By the way, the above-mentioned series reactor has been used exclusively in a situation where the amount of harmonics before the practical use of the inverter or the like is small, and the series reactor is used rapidly. Due to the widespread use, it is not possible to effectively cope with the situation in which the harmonics are significantly increasing, and it is said that not only the phase-advancing capacitor but also the series reactor itself as a countermeasure against it will be burnt out by heating.

That is, when a commonly used series reactor (6% L) is used, the combined impedance of the capacitor and the reactor at the fifth harmonic is only 10% of the reactance value of the capacitor at the fundamental frequency. . Therefore, the series reactor in this case merely serves as an inductive load when the capacitor circuit is viewed from the power supply, and has no effect on suppressing the harmonic current flowing into the capacitor circuit.

Furthermore, even if a 13% series reactor is used, its composite impedance is only 45%, and in order to have a composite impedance of the same value as the reactance value of the capacitor at the fundamental frequency in the fifth long wave, 24%
Reactor must be used. If the 24% reactor is used, the reactor reactance is not only increased, but a reactor voltage drop occurs at the fundamental frequency, and further, the capacitor becomes overheated when the voltage becomes larger than the 6% reactor. Further, iron loss of the reactor (hysteresis loss, eddy current loss) becomes large, and cooling becomes a problem.

As described above, the series reactor has a low suppressing ability and does not exhibit a sufficient suppressing effect. Therefore, in the past, in addition to using a series reactor, the capacitor circuit was unified into a flame-retardant device, a protection circuit for temperature rise detection was provided, and a circuit for detecting abnormality of the capacitor was provided to open the circuit. It was necessary to take measures such as preventing power outages and monitoring harmonic levels using a harmonic checker.

Further, the series reactor has iron loss at the fundamental frequency, is large in size and heavy in weight, and is expensive.
For example, the reactance of the fifth harmonic is only 5 times the reactance of the fundamental frequency, and the cross-sectional area of the iron core of the main magnetic path must be determined from the sum of the fundamental frequency magnetic flux and the harmonic magnetic flux. Since the design is troublesome and there is a gap, there is a problem that the noise is larger than that of the transformer.

It is an object of the present invention to provide a harmonic current suppressor which has a large capability of suppressing harmonic current and which can be made compact and lightweight.

[0011]

According to the present invention, two coils, which are inserted between a load and a power source and connected in parallel, are arranged in the same annular main magnetic path by being wound in the same direction, Further, the harmonic current suppressor is characterized in that an annular bypass magnetic path having a smaller saturation magnetic flux amount than the main magnetic path is formed in each coil from the inside to the outside thereof.

As an example of such a harmonic current suppressor, two coils inserted between a load and a power source and connected in parallel are wound around the same annular main iron core in the same direction. A bypass iron core, which is provided and has a smaller saturation magnetic flux amount than the annular main iron core, can be configured by bridging the annular main iron core such that the front and rear of both coils are short-circuited.

[0013]

[Function] When a current of a fundamental frequency flows through both coils, magnetic flux is generated, but since the magnetic flux directions of both coils are opposite,
The main magnetic paths cancel each other. Therefore, no back electromotive force is generated by this main magnetic path. On the other hand, although the magnetic flux also flows in the annular bypass magnetic path, the saturation magnetic flux amount in this magnetic path is small, and therefore the magnetic flux amount due to the fundamental frequency component is large, so that the magnetic flux enters the saturated state directly and there is no change in the magnetic flux. No back electromotive force is generated. Therefore, the inductance with respect to the fundamental frequency is small.

On the other hand, when a harmonic wave flows through both coils, the harmonic wave cannot saturate the annular bypass magnetic path, so that a counter electromotive force is generated by the annular bypass magnetic path. For this reason, the inductance with respect to harmonics becomes large.

Therefore, when a current is passed through this harmonic current suppressor, only the harmonic wave receives the counter electromotive force by the annular bypass magnetic path, and only the harmonic current is reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to the accompanying drawings.

1 and 2 show an embodiment of the present invention.

Here, the harmonic current suppressor 1 according to the present invention
Is inserted between the load L and the power source S. The harmonic current suppressor 1 is provided by winding two coils 2 and 2 connected in parallel on both sides of the same rectangular annular main iron core 3 in the same direction. Then, the upper and lower parts of the annular main iron core 3 are bridged by the bypass iron core 4 to short-circuit the front and rear of the coils 2, 2. The bypass iron core 4 has a cross-sectional area of
It is made smaller than the cross-sectional area of the annular main iron core 3, thereby making the bypass iron core 4 have a smaller saturation magnetic flux amount than the annular main iron core 3. As will be described later, the annular main iron core 3 constitutes an annular main magnetic path, and the annular main iron core 3 and the bypass iron core 4 constitute annular bypass magnetic paths 5, 5.

Next, general characteristics of such a configuration will be described.

A) When magnetic saturation does not occur

When a voltage is applied to each of the coils 2 and 2, a current flows and a magnetic flux is generated, but in the main magnetic path, the phases of both windings are opposite and the directions of the magnetic flux are opposite to each other. The magnetic flux of the wire flows to the bypass iron core 4 having a low magnetic resistance and is added. Here, if the bypass iron core 4 has a cross-sectional area that satisfies the following expression (1), the magnetic flux should recirculate in the annular bypass magnetic paths 5, 5 composed of the annular main iron core 3 and the bypass iron core 4. Then, the counter electromotive force is generated in the coils 2 and 2, and the inductance of the winding is expressed by the equation (2). Here, the arrow in FIG. 1 indicates the path of the magnetic flux.

S = E / (2 ^1/2 πfNB) (1)

Here, S; sectional area [m ² ] E; voltage [V] f; frequency [Hz] N; number of turns B; magnetic flux density [Wb / m ² ]

L = 4πN ² Sμ _s × 10 ⁻⁷ / l (2)

Here, L; inductance [H] S;
Bypass iron core cross-sectional area [m ² ] μ _s ; Bypass iron core relative permeability 1; Iron core magnetic path length [m]

B) When magnetic saturation occurs

When the magnetic flux generated in the coils 2 and 2 accompanying the voltage application flows to the bypass iron core 4 (bypass magnetic paths 5 and 5) having a low magnetic resistance, the bypass iron core 4 (bypass magnetic path 5 , 5) has a cross-sectional area smaller than the cross-sectional area satisfying the expression (1), the bypass magnetic path is in a magnetic saturation state. The magnetic saturation start angle at this time is shown in Expression (3).

Α = 2 × sin ⁻¹ (4.44 fNBS / E) ^1/2 (3) where α: magnetic saturation start angle

When magnetic saturation occurs in the bypass magnetic paths 5 and 5, the magnetic resistance remarkably increases, so that the magnetic fluxes do not pass through the bypass iron core 4 and cancel each other out on the main magnetic path (main iron core 3). At this time, a part of the magnetic flux recirculates without canceling each other and becomes a leakage magnetic flux. The voltage drop due to the leakage flux can be calculated by the same formula as the transformer reactance. Therefore, the reactance can be reduced by arranging the coils 2 and 2 coaxially symmetrically or alternately. FIG. 2 shows the path of magnetic flux.

The inductance of the winding at this time is obtained by dividing the reactance obtained by the following equation (4) by 2πf.

X _L = 7.9 fN ² U _m κ (d + 2a / 3) × 10 ⁻⁶ / h (4)

Where X _L ; leakage reactance [Ω]
U _m ; average circumference of coil [m] κ; Rogowski coefficient d; interval length of coil [m] a;
Coil thickness [m] h; Coil height [m]

The harmonic current suppressor 1 has the above-mentioned characteristics. Therefore, the response characteristics to the actual current will be described.

When a power supply voltage is applied, the magnetic flux generated in the coils 2 and 2 of the fundamental frequency component therein is large, and therefore, the bypass iron core 4 has a magnetic saturation start angle determined by the equation (3). Causes magnetic saturation. Then, when magnetic saturation occurs in the bypass iron core 4, the magnetic resistance becomes remarkably large, the leakage magnetic flux is removed without passing through the bypass magnetic path, and the annular main iron core 3 cancels each other. Therefore, the reactance of the coils 2 and 2 becomes substantially equal to the leakage reactance during the magnetic saturation period, and has almost no effect on the fundamental frequency current of the circuit. Therefore, if the windings are arranged alternately for the voltage drop, the leakage reactance of the transformer is usually 2
Since it is ~ 5%, it can be paid to about 4%. Further, it is possible to further reduce the size by adopting a coil structure such as an alternating arrangement.

On the other hand, since the magnetic flux due to the harmonic voltage does not cause magnetic saturation in the bypass magnetic path, only the harmonic magnetic flux flows back through the bypass magnetic path without canceling each other.
Therefore, the harmonic current is suppressed by the exciting inductance determined by the equation (2). Since the target frequency is several times higher than the commercial frequency, it is not difficult to suppress the exciting current to 5% or less of the circuit current, and a winding core type bypass magnetic path is adopted. Then
It can be easily reduced to 1% or less.

Further, the ratio of the reactance in the harmonic to the reactance in the fundamental frequency is at least 100 times or more, and the reactance change of the harmonic current suppressor 1 is compared with the fact that the reactance of an ordinary reactor is approximately proportional to the frequency. The size of is understood.

FIG. 5 shows a harmonic current suppressor 1 having such a configuration.
And the reactance with other conventional equipment. From this figure, it can be seen that as the harmonic order increases, the reactance for the harmonic increases.

FIG. 6 compares the currents of the harmonic current suppressor 1 and other conventional devices. Where f ₁
The (fundamental frequency) is better as it is closer to 1, and the smaller f _{3 to} f ₁₁ is, the better.

Further, FIG. 7 compares the synthetic current with the resonance frequency. The smaller this combined current, the better,
Moreover, it is better that there is no resonance frequency.

In the above-mentioned configuration, the bypass magnetic core 4 constitutes the bypass magnetic path, but at the fundamental frequency, the bypass iron core 4 only serves as a saturation path, The magnetic fluxes generated in 2 and 2 cancel each other out in the main magnetic path on the annular main iron core 3. Therefore, the bypass iron core 4 has the following relationship with the harmonic voltage:
It can be said that it has meaning for the first time. Therefore, a bypass magnetic path may be provided separately from the annular main iron core 3. 3 and 4 show an example thereof.

That is, the coils 2, 2 are provided with an annular main magnetic path 11 made of an annular main iron core, and each coil 2, 2
In addition, the annular bypass magnetic path 10 having a smaller saturation magnetic flux amount than the main magnetic path 11 is formed from the inside to the outside thereof. The annular bypass magnetic paths 10 and 10 are made of a flexible thin film metallic material made of an amorphous metal or the like whose cross-sectional area can be made significantly smaller than that of the annular main magnetic path 11 so that the saturation magnetic flux amount becomes small. Using the coils 2, 2
It can be easily constructed by winding the inner and outer peripheries of the same through an insulating material. Even with this configuration, the magnetic fluxes generated at the fundamental frequency are canceled out on the annular main magnetic path 11 and the annular bypass magnetic paths 10 and 10 of the coils 2 and 2 are saturated. On the other hand, in the case of harmonics, the magnetic flux circulates while maintaining the non-saturated state in each of the annular bypass magnetic paths 10 and 10, and the harmonic current is excited by the equation (2) similarly to the above. It is suppressed by the inductance, and
Only the harmonic current will be reduced.

FIG. 4 shows a concrete example of such a structure, in which U-shaped metal pieces 14, 14 are abutted against each other via insulating layers 13, 13 inside and outside the coils 2, 2 to form an annular structure. Thus, the annular bypass magnetic path 10 is provided around.
The annular bypass magnetic path 10 is also insulated from the main magnetic path 11 by the insulating layer 15.

The annular bypass magnetic paths 10 and 10 are constituted by a flexible thin film metal material, an annular iron plate or the like. Further, the magnetic powder may be held in a ring shape.

[0044]

According to the present invention, two coils, which are interposed between a load and a power source and connected in parallel, are arranged in the same annular main magnetic path so as to be wound in the same direction, and the respective coils are provided. From the inside to the outside, since an annular bypass magnetic path having a smaller saturation magnetic flux amount than the main magnetic path is formed, when a current of a fundamental frequency flows in both coils, they cancel each other out in the main magnetic path, When the higher harmonic wave flows through both coils, the higher harmonic wave cannot saturate the annular bypass magnetic path, so that the counter electromotive force is generated by the annular bypass magnetic path, and the inductance for the higher harmonic wave increases. Therefore, only the harmonic current can be effectively reduced. Comparing this with a conventional series reactor, not only is the ability to suppress harmonic currents dramatically improved, but iron loss does not occur at the fundamental frequency, and noise occurs only in the bypass magnetic path. It is small, the cross-sectional area of the iron core can be made small, the size and weight can be small, and the structure is simple, lightweight and inexpensive.
Further, there are advantages such as easy design.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a non-saturated state of a first embodiment.

FIG. 2 is a circuit diagram showing a saturated state of the first embodiment.

FIG. 3 is a circuit diagram of a second embodiment.

FIG. 4 is a vertical sectional side view of a main part.

FIG. 5 is a comparison diagram of reactances of the present invention and a conventional device.

FIG. 6 is a comparison diagram of currents of the present invention and a conventional device.

FIG. 7 is a comparison diagram of a synthetic current and a resonance frequency of the present invention and a conventional device.

FIG. 8 is a waveform diagram showing how the distorted waveform C is formed.

[Explanation of symbols]

 1 Harmonic current suppressor 2, 2 Coil 3 Annular main iron core (annular main magnetic path) 4 Bypass iron core 5, 5 Annular bypass magnetic path 10, 10 Annular bypass magnetic path 11 Annular main magnetic path

Claims (2)

[Claims] 1. Two coils, which are inserted between a load and a power source and connected in parallel, are arranged in the same annular main magnetic path so as to be wound in the same direction, and each coil is arranged from the inside thereof. A harmonic current suppressor characterized in that an annular bypass magnetic path having a smaller amount of saturation magnetic flux than the main magnetic path is formed outward. 2. Two coils, which are inserted between a load and a power source and are connected in parallel, are wound around the same annular main iron core in the same direction, and are arranged in the same direction. 2. The harmonic current suppressor according to claim 1, wherein the bypass iron core having a small saturation magnetic flux amount is bridged to the annular main iron core by short-circuiting the front and rear of both coils.