JP5809860B2 - Noise filter - Google Patents

Description

  The present invention relates to a noise filter connected in parallel between distribution lines, and in particular, in addition to absorbing transient fluctuations such as spikes and surges applied to the so-called fundamental voltage of distribution lines, the so-called basics of distribution lines. The present invention relates to a noise filter that filters high-frequency noise superimposed on a wave voltage.

  Distribution lines are easy to react to spikes, surges, and high-frequency noise, but at the same time, machines and devices connected to distribution lines themselves generate transient fluctuations such as spikes and surges, so-called basics of distribution lines. It will be superimposed on the wave voltage. Also when the switch is turned off and turned on, an electrical impulse is superimposed on the so-called fundamental voltage of the distribution line. When starting and stopping the motor, a surge is caused, and the AC waveform of the distribution line is distorted by harmonics generated by power converters that drive various motors. In this way, the alternating current of the distribution line is distorted by these types of spikes, surges, etc., and reduces the efficiency of the motor and other equipment. Moreover, high frequency noise is easily superimposed on the distribution line. High-frequency noise is an unnecessary voltage or current component superimposed on alternating current, and is generated from an electronic device, a control circuit, a switching power supply, or the like. In addition, high frequency noise can cause problems such as data errors and device malfunctions.

JP 2004-159376 A

  An object of the present invention is to provide a noise filter that can absorb transient fluctuations such as spikes and surges applied to a distribution line and remove high-frequency noise superimposed on the distribution line.

  The noise filter according to the present invention is a noise filter connected in parallel between distribution lines, connecting a series connection body of an overcurrent cutoff element and an overvoltage absorption element between the distribution lines, and the overvoltage absorption element, A series connection body of a capacitor and a resistor and a light emitting device are connected in parallel.

  The overcurrent interruption element is not particularly limited, but is preferably a fuse.

  The overvoltage absorbing element is not particularly limited, but is preferably a metal oxide varistor.

  In the noise filter of the present invention, the capacitor acts with an inductance component of the distribution line to constitute at least a secondary low-pass filter, and high frequency noise superimposed on the distribution line can be removed.

  If the resistor is formed of a resistor having a low inductance, the attenuation characteristic of the noise filter does not need to be deteriorated even in the high frequency region. This resistance can be constituted by a plate-like resistance or a non-inductive resistance.

  The distribution line is a pair of distribution lines between an AC power source and a load, and the wiring inductance of the pair of distribution lines, the capacitor in the noise filter connected in parallel between the distribution lines, and the When the attenuation coefficient of the transfer function of the circuit composed of the resistor and the load is selected to be 0.7 or more, the noise superimposed on the wiring can be effectively attenuated.

  It is preferable that the capacitance value and the resistance value of the capacitor are set so that a time constant that is a product of the capacitance value (μF) and the resistance value (Ω) of the resistor is 10 to 40 (μ seconds). . For example, the capacitance value of this capacitor can be set to 10 to 30 (μF). In the time constant range, if the wiring inductances on the power supply side and the load side to which the noise filter is connected are considered to be about 0.2 mH, the cutoff frequency of the noise filter can be about 3 kHz.

  It is preferable that a second capacitor and a series connection of a second resistor are further connected in parallel to the resistor. In this case, the capacitor and the second capacitor interact with the inductance component of the distribution line to form a third-order low-pass filter, and the high-frequency noise superimposed on the alternating current flowing through the distribution line can be more sharply removed. .

  When the distribution line is a three-phase distribution line and each noise filter is connected between each phase line in the three-phase distribution line, it is preferable to connect each noise filter in a delta connection.

  By preventing the ground current from flowing between the components constituting the noise filter and the ground, it is possible to contribute to the improvement of the performance of the noise filter. Since the case of the noise filter is grounded, for example, it is preferable to prevent a ground current from flowing between the part and the case. As the method, it is conceivable to arrange the component in a state where it is floated from the case, or to interpose an insulating material between the component and the case.

  In the noise filter of the present invention, transient fluctuations such as spikes and surges applied between distribution lines can be absorbed by an overvoltage absorbing element such as a metal oxide varistor, and the capacitor acts on the inductance component of the distribution line. Accordingly, since the low-pass filter can be configured, the high-frequency noise superimposed on the distribution line can be suppressed or removed by the low-pass filter. An overcurrent interrupting element such as a fuse is provided in order to prevent a fire when the overvoltage absorbing element or the low-pass filter is damaged by a short circuit. Further, the light emitting device is provided so that it does not emit light when the overcurrent interrupting element interrupts the current, and it is possible to visually confirm whether or not the noise filter is in operation.

FIG. 1 is a circuit diagram of a noise filter according to an embodiment of the present invention. FIG. 2A is an AC waveform diagram in which a transient overvoltage is applied, and FIG. 2B is an AC waveform diagram in which the transient overvoltage is clamped. 3A is an AC waveform diagram in which high-frequency noise is superimposed, and FIG. 3B is an AC waveform diagram from which high-frequency noise is removed. FIG. 4 is a circuit diagram of a noise filter according to another embodiment. FIG. 5 is a frequency vs. gain characteristic diagram of the noise filter of FIG. FIG. 6 is a circuit diagram of a noise filter according to still another embodiment.

  Hereinafter, a noise filter according to an embodiment of the present invention will be described with reference to the accompanying drawings. Referring to FIG. 1, a noise filter 5 is connected between a pair of distribution lines 3 and 4 between an AC power supply 1 and a load 2. The distribution lines 3 and 4 have inductance, and the inductance component is indicated by L in the figure. The noise filter 5 includes a first series connection body 8 including a fuse 6 and a metal oxide varistor 7 connected in parallel between the distribution lines 3 and 4, a capacitor 9 connected in parallel to the metal oxide varistor 7, and A second series connection body 11 of the resistor 10 and a light emitting device 12 connected in parallel to the metal oxide varistor 7 are included.

  When the metal oxide varistor 7, the capacitor 9, the resistor 10, and the light emitting device 12 are damaged as a short circuit, the fuse 6 in the first series connection body 8 generates heat and blows out, and the noise filter 5 To prevent fire.

  The metal oxide varistor 7 has a high resistance value as an overvoltage absorbing element when an overvoltage such as a surge is not applied to the alternating current, and when the overvoltage is applied, the resistance becomes very low, and the overvoltage is clipped. Absorb.

  The capacitor 9 in the second series connection body 11 works with the inductance L of the distribution lines 3 and 4 to form a low-pass filter that removes high-frequency noise superimposed on alternating current. In this case, the resistor 10 is also included in the low-pass filter.

  The resistor 10 has an angular frequency ω, the capacitance of the capacitor 9 is C, and does not resonate in the vicinity of ωL = 1 / ωC so that no overcurrent flows between the distribution lines 3 and 4. That is, resonance is suppressed.

  The wiring inductance 2L of the pair of distribution lines 3 and 4, the capacitance C of the capacitor 9 and the resistance value R1 of the resistor 10 in the noise filter 5 connected in parallel between the distribution lines 3 and 4, If the attenuation coefficient of the transfer function of the circuit constituted by the resistance value R2 of the load 2 is selected to be 0.7 or more at which resonance does not appear, noise on the wiring can be attenuated. In this case, the load 2 is equivalently a resistance.

  If the resistor 10 is a resistor having a low inductance, the attenuation characteristics do not need to deteriorate even in the high frequency region. As the resistor 10, for example, a plate-like resistor or a non-inductive resistor can be used.

  The capacitance value (μF) of the capacitor 9 is preferably set so that the time constant, which is the product of the capacitance value and the resistance value (Ω) of the resistor 10, is 10 to 40 (μsec). The capacitor 9 preferably has a capacitance value in the range of 10 to 40 (μF). With such a time constant, when the total wiring inductance on the power supply side and load side to which the noise filter is connected is considered to be about 0.2 mH, the cutoff frequency of the noise filter is about 1 to 5 kHz. can do.

  When the resonance does not occur, the resistor 10 is not necessarily essential and can be omitted.

  The light emitting device 12 is not particularly limited, and any element that can emit light when a current flows can be used.

In the embodiment, a secondary low-pass filter is configured by the inductance component L of the distribution lines 3, 4, the capacitance of the capacitor 9, and the resistance of the resistor 10 to suppress or remove high-frequency noise superimposed on alternating current. Can do.

  FIG. 2A is an AC waveform diagram distorted by a transient voltage. In the noise filter 5 of the embodiment, even if a transient voltage is applied to the distribution lines 3 and 4, as shown in FIG. 2 (b), a dotted line is shown at a location where the noise filter 5 is connected by the metal oxide varistor 7. Clipped to a predetermined voltage of the level indicated by and absorbed. The metal oxide varistor 7 appears as an infinitely high resistance in the circuit before the transient voltage occurs. When a transient voltage is applied, the metal oxide varistor 7 becomes a very low resistance element and clips the transient voltage. When the transient voltage is no longer applied, the metal oxide varistor 7 returns to a high resistance element. The metal oxide varistor 7 becomes a very low resistance element, and substantially clamps the voltage between the distribution lines 3 and 4 to a predetermined value.

  The light emitting device 12 emits light with a current flowing from the distribution lines 3 and 4 in a state where the fuse 6 is not blown. The light emitting device 12 stops emitting light when the fuse 6 is blown or no current flows. By the light emission of the light emitting device 12 and its stop, the user can know the application state of the overvoltage and others.

  Next, FIG. 3A is a diagram illustrating a state in which high-frequency noise is superimposed on the distribution lines 3 and 4. The noise filter 5 forms a secondary low-pass filter by the capacitor 9 and the resistor 10 together with the inductance component L of the distribution lines 3 and 4, and removes high-frequency noise from the alternating current as shown in FIG. . In the embodiment, the inductance component L of the distribution lines 3 and 4 is used to configure the secondary low-pass filter without separately providing an inductor as a lumped constant element. The capacitance of the capacitor 9 and the resistance value of the resistor 10 can be set according to the frequency of the high frequency noise.

FIG. 4 is a circuit diagram of a noise filter according to another embodiment of the present invention. Referring to FIG. 4, in the noise filter 5a of this embodiment, a third series connection body 15 of a second capacitor 13 and a second resistor 14 is connected in parallel to the resistor 10 in the noise filter 5 of the above embodiment. It is a thing. Thereby, the noise filter 5a of the embodiment includes the inductance component L of the distribution lines 3 and 4, the capacitance of the capacitor 9, the resistance of the resistor 10, the capacitance of the second capacitor 13 , and the resistance of the second resistor 14 . A third-order low-pass filter is configured. In the embodiment of FIG. 4, unlike the secondary low-pass filter in the noise filter 5 of FIG. 1, high-frequency noise can be more sharply removed from the distribution lines 3 and 4.

  FIG. 5 is a diagram showing the frequency-gain characteristics of the noise filter 5 and the noise filter 5a. A shows the characteristics of the noise filter 5, and B shows the characteristics of the noise filter 5a. The cutoff frequency of the noise filter 5 is fc1. The cutoff frequency of the noise filter 5a is fc2. In this embodiment, the addition of the capacitor 13 makes it possible to remove the high-frequency noise from the distribution lines 3 and 4 more sharply.

  When the total capacity of the capacitors 9 and 13 is set so that the time constant, which is the product of the total capacity value and the total resistance value (Ω) of the resistors 10 and 15, is 10 to 40 (μsec), When the total of the wiring inductance on the load side and the load side is considered to be about 0.2 mH, the cut-off frequency of the noise filter can be set to about 1 to 5 kHz. In this case, the total capacitance value of the capacitors 9 and 13 is 10 to 30 (μF).

  FIG. 6 is a circuit diagram of a noise filter according to still another embodiment of the present invention. The noise filter in FIG. 6 is delta-connected to the noise filter 5 in FIG. 1 and between each phase line (distribution line) 18 to 20 between the three-phase power source 16 and a three-phase motor 17 that is an example of a three-phase load. They are connected to each other. In FIG. 6, the noise filter 5 is connected between the phase lines 18 to 20, but of course, the noise filter 5 a may be connected.

  In the noise filter of the embodiment, it is preferable that no ground current flows. Therefore, it is preferable that components constituting the noise filter of each embodiment have a sufficiently large insulation resistance with respect to the ground.

DESCRIPTION OF SYMBOLS 1 Power supply 2 Load 3, 4 Distribution line 5 Noise filter 6 Fuse 7 Metal oxide varistor 8 1st series connection body 9 Capacitor 10 Resistance 11 2nd series connection body 12 Light emitting device

Claims (2)

A noise filter connected between a pair of distribution lines,
Between the distribution lines, connecting a series connection body of an overcurrent interruption element and an overvoltage absorption element,
A serial connection body of a capacitor and a resistor, and a light emitting device are connected in parallel to the overvoltage absorbing element ,
A secondary low-pass filter is constituted by the inductance component of the distribution line, the capacitance of the capacitor and the resistance,
A noise filter, wherein the resistor is a plate-like resistor or a low-inductance resistor that is a non-inductive resistor . A noise filter connected between a pair of distribution lines,
Between the distribution lines, connecting a series connection body of an overcurrent interruption element and an overvoltage absorption element,
A serial connection body of a capacitor and a resistor and a light emitting device are connected in parallel to the overvoltage absorbing element, and a second capacitor and a second resistor connected in series to the resistor are connected in parallel.
A third-order low-pass filter is constituted by the inductance component of the distribution line, the capacitance of the capacitor, the resistance, the capacitance of the second capacitor, and the second resistance,
A noise filter, wherein the resistor is a plate-like resistor or a low-inductance resistor that is a non-inductive resistor .

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