JPH09102723A - Line filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and lightweight line filter which can eliminate electromagnetic wave noises and also can shape the waveform by connecting a series transformer between an AC power supply and a load to make the phase reverse to the power voltage. SOLUTION: The secondary winding of a series transformer TR is connected in series between an AC power supply 1 and a load L as a means that shapes the waveform of the power voltage E1, so that the phase difference is set to 180 deg. against the voltage E1. In such a constitution, the power source higher harmonics and the electromagnetic noise component passing through a filter circuit 2 of the voltage E1 are subtracted from the power supply via the TR. The noise component E2 is removed out of the voltage E1 and the load voltage E4 is obtained. Therefore, only the sine wave voltage is applied to the load L. As a result, the power source higher harmonics and the electromagnetic noises entering from a power line and a signal line can be eliminated and also the waveform of the inverter output, etc., can be shaped in a comparatively simple way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform of a line filter or an inverter output for removing power source harmonics and electromagnetic noise intruding from a power source line or a signal line, which have become a problem in recent years due to the increase of digital equipment. Relating to a line filter for shaping.

[0002]

2. Description of the Related Art Most conventional line filters mainly combine a reactor, a capacitor and a resistor.

[0003]

However, in the conventional line filter, the higher the power becomes, the more difficult it is to remove power source harmonics and electromagnetic noise and to shape the waveform of the inverter output. Therefore, the object of the present invention is to solve the above problems, to remove electromagnetic noise that intrudes from power supply harmonics and power supply lines and signal lines, and to perform waveform shaping such as inverter output with a relatively simple method. The purpose of the present invention is to improve the size, weight, conversion efficiency, reliability, manufacturing cost, etc. of a conventional line filter, and bring about an economic effect in various fields.

[0004]

In the line filter of the present invention, the secondary winding of a series transformer is connected in series between the AC power supply and the load in a reverse polarity to the power supply as a means for shaping the power supply waveform. , The input side of the filter circuit is connected to the AC power supply, and the output side of the filter circuit is connected to one of the series transformers.
It is connected to the next winding.

[0005]

The line filter of the present invention having the above-mentioned structure passes through the filter circuit for the power supply voltage by inserting the series transformer between the AC power supply and the load so as to have a phase opposite to the power supply voltage. Only clean sine wave voltage is applied to the load because power supply harmonics and electromagnetic noise components are subtracted from the power supply through the series transformer.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Example) The line filter of the example is
As shown in FIG. 1, the secondary winding of the series transformer TR is connected in series between the AC power supply 1 and the load L so as to shape the power supply waveform so that the phase difference from the power supply voltage is 180 °. Connect, connect the input side of the filter circuit 2 to the AC power supply 1,
The output side of the filter circuit 2 is connected to the primary winding of the series transformer TR.

FIG. 2 (a) shows the waveform of the power supply voltage E1 and FIG.
When − (b) is the waveform of the output voltage E3 of the filter circuit 2, the load voltage E4 is given by the following equation. E4 = E1-E2 As can be seen from this equation, the noise component E from the power supply voltage E1
The voltage obtained by removing only 2 is the load voltage. The filter circuit 2 is a simple combination of a reactor, a capacitor, and a resistor, or an active filter circuit using an operational amplifier. The AC power supply may be a sine wave from which noise is removed even if it is a square wave, a triangular wave or other distorted waveform of the inverter output, instead of a sine wave. The same effect can be obtained by applying the above embodiment to a single-phase three-wire power supply, a three-phase power supply, and a three-phase four-wire power supply. The same noise removal effect can be obtained with the signal line.

[0009]

According to the present invention having the above-described operation, the capacity of the filter circuit is reduced by inserting the series transformer between the AC power supply and the load so as to have a phase opposite to the power supply voltage. In addition, high-performance active filters used in electronic circuits can also be used for electric power, and in the future, high performance, small size, light weight, high efficiency, and low cost of line filters can be significantly achieved.

[Brief description of the drawings]

FIG. 1 is an electric circuit block diagram showing an entire embodiment of the present invention.

FIG. 2 is a diagram showing voltage waveforms according to an embodiment of the present invention.

[Explanation of symbols]

 1 is AC power source 2 is filter circuit TR is series transformer L is load

Claims (1)

[Claims] 1. A secondary winding of a series transformer is connected in series between an AC power supply and a load as a means for shaping a power supply waveform, and an input side of a filter circuit is connected to the AC power supply, A line filter, characterized in that the output side of the circuit is connected to the primary winding of the series transformer.