JPH01293005A - Harmonic filter - Google Patents

Abstract

PURPOSE:To obtain a harmonic filter which has excellent higher harmonic absorbing characteristics and can be miniaturized by constituting an inductance with a superconducting coil. CONSTITUTION:A series resonance circuit is constituted of the superconducting coil 6 and a capacitance 2. The frequency characteristics of the resultant impedance of the coil 6 and capacitance 2 show the lowest impedance Z0 at a resonance frequency fo as indicated by the Z1+2 of the appended figure. The frequency characteristics of power source impedance Z4, moreover, is as shown in the figure. Therefore, when the resonance frequency fo which can be set by using the L-value of the coil 6 and C-value of the capacitance 2 is selected so that the frequency fo can coincide with the frequency of a higher harmonic current, the value of the power source impedance Z4 becomes Zo at the resonance frequency fo. Therefore, it is possible to cause the higher harmonic current In flowing out of a nonlinear load 5 to be absorbed by the series resonance circuit so that the current cannot flow out to a power source.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a harmonic filter.

[Conventional technology]

Figure 3 is a circuit diagram showing a conventional harmonic filter. In the figure, 1 is the inductance, 2 is the inductance 1
This capacitance 2 and inductance 1 constitute a series resonant circuit. 3 is a power supply, 4 is an impedance of the power supply 3, and 5 is a nonlinear load, and this nonlinear load 5 is grounded via a series resonant circuit.

Next, the operation will be explained. The frequency characteristic of the composite impedance z1+2 of inductance 1 and capacitance 2 is the resonance frequency f, as shown as 21+2 in Figure 4.
It is well known that the minimum impedance Zo is 0. On the other hand, the frequency characteristic of impedance 4 of the power supply is
It is shown as Z in the figure. The value of inductance 1 and the value C of capacitance 2 are selected to match the resonance frequency f0, and at the resonance frequency f0, the value of power supply impedance Z4 is 2. > 2°, the harmonic current In flowing out from the nonlinear load 5 is absorbed into the inductance 1 and capacitance 2 side, and is prevented from flowing to the power source 3 side as much as possible.

[Problem to be solved by the invention]

Since the conventional harmonic filter is configured as described above, the harmonic current flowing out to the power supply 3 side is the harmonic type flowing out from the nonlinear load 5.
), and the power supply impedance Z4 is determined by the conditions of the power supply 1, and cannot be arbitrarily selected within a wide range. Therefore, in order to improve the filter performance, the minimum impedance Zo must be made smaller. However, there is a problem in that the minimum impedance Z0 is almost limited by the internal resistance of the inductance 1 and the iron loss of the iron core used for the inductance 1, and cannot be reduced indefinitely.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a harmonic filter that is small and has good absorption characteristics.

[Means to solve the problem]

The harmonic filter according to the present invention is one in which the inductance of a series resonant circuit is composed of a superconducting coil.

[For production]

Since the inductance in this invention has low loss,
Low impedance can be obtained, and good absorption characteristics can be obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, the capacitance 2, the power source 3, the impedance 4 of the power source 3, and the nonlinear load 5 are the same as those in the conventional example shown in FIG. 3, so their explanation will be omitted. A superconducting coil 6 is connected in series with the capacitance 2, and the superconducting coil 6 and the capacitance 2 constitute a series resonant circuit.

Next, the operation will be explained.

The frequency characteristics of the combined impedance of the superconducting coil 6 and the capacitance 2 are as shown in FIG. 2 as 21+1, which shows the lowest impedance Z0 at the resonance frequency f0, and the frequency characteristics of the power supply impedance Z4 are as shown in FIG. . Therefore, by selecting the resonant frequency f0, which can be set by the L value of the superconducting coil 6 and the C value of the capacitance 2, to match the frequency of the harmonic current to be absorbed, the value of the power supply impedance Z4 can be changed to Z at the resonant frequency fo. ->Zo. Therefore, the harmonic current In flowing out from the nonlinear load 5 can be absorbed by the series resonant circuit side, and can be prevented from flowing out to the power supply 3.

〔Effect of the invention〕

As described above, according to the present invention, since the inductance of the series resonant circuit is constituted by a superconducting coil, it is possible to obtain an apparatus which has very good harmonic absorption characteristics and can be miniaturized.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a harmonic filter according to an embodiment of the present invention, Figure 2 is its frequency characteristics, Figure 3 is a circuit diagram showing a conventional harmonic filter, and Figure 4 is its frequency characteristics. . 2 is a capacitance, and 6 is a superconducting coil. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Figure 1 og f

Claims (1)

[Claims] In a harmonic filter that absorbs current at a specific frequency by taking advantage of the fact that the impedance decreases at the series resonance point of a series resonant circuit in which an inductance and a capacitance are connected in series, the above inductance is constructed with a superconducting coil. Characteristic harmonic filter.