JP2007300700A - Noise reducing reactor and noise reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise reducing reactor which can reduce noise generated by an inverter device and a load, without causing an increase in the number of part items, which is inexpensive and can be reduced in size, and to provide a noise reducing device. <P>SOLUTION: The noise reducing reactor La is inserted into a power supply cable from a three-phase four-line type AC power supply 1, reduces the noise that propagates to the power supply cable, and comprises a first magnetic core 5a, having a penetration hole 51 at its center and forming a first closed magnetic passage; a first winding 10R, a second winding 10S, a third winding 10T and a fourth winding 10N, which are arranged so as to correspond to the power supply cable from the three-phase four-line type AC power supply 1, and wound to the first magnetic core 5a; a second magnetic core 6a, which is inserted into the penetration hole 51 of the first magnetic core 5a, passes a part of the first closed magnetic passage of the first magnetic core 5a at each winding, and forms a second closed magnetic passage; and an insulating body 7a, set up between the first magnetic core 5a and the second magnetic core 6a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise reduction reactor and a noise reduction device which are inserted into a power supply line from a three-phase four-wire AC power supply and reduce noise propagated to the power supply line.

  FIG. 8 shows a connection diagram of a general motor. The inverter device 3 converts the power supplied from the three-phase AC power source 1 into a predetermined power and supplies it to the motor 4.

  In this power conversion device, the inverter device 3 converts power by turning on / off a switching element (not shown), so that switching noise is generated due to switching of the switching element. Since the frequency of the switching noise is very high, the noise is suppressed to a level that does not adversely affect other peripheral devices by using the filter circuit 2 having a wide band and a large attenuation characteristic.

  Further, the inverter device 3 and the motor 4 have a capacitance including a stray capacitance between the ground and switching noise due to switching of the switching element via the capacitance becomes a high-frequency leakage current to the ground line. Flowing. When this leakage current flows through the ground line, the voltage level of the frame (housing) of the inverter device 3 varies. When this leakage current is large, the leakage breaker is cut off.

  In order to reduce such noise, a filter circuit composed of a capacitor and a reactor is usually used. FIG. 9 is a conventional filter circuit composed of a capacitor and a reactor. A filter circuit 2a shown in FIG. 9 includes a line-to-line capacitor 21a to 21c and common mode coils 22a and 22b between a three-phase four-wire three-phase AC power source 1 including three phase power sources 11 to 13 and an inverter device 3. The line-to-ground capacitor 23 is provided. Inter-line capacitors 21a to 21c include capacitors C11 to C19 that reduce normal mode noise flowing between the R, S, T, and N phases. The line-to-earth capacitor 23 includes capacitors C20 to C23 that reduce common mode noise flowing between the R, S, T, and N phases and the ground E (earth).

  As shown in FIG. 9, line-to-line capacitors 21a to 21c, line-to-ground capacitor 23 and common mode coils 22a and 22b are provided to ensure a noise reduction effect. However, this configuration uses a large number of line-to-line capacitors 21a to 21c and common mode coils 22a and 22b, resulting in a large circuit.

  For this reason, devices that reduce common mode noise using active elements are known (Patent Documents 1 and 2). FIG. 10 is a conventional filter circuit diagram including a common mode noise current detector (hereinafter abbreviated as CT) and a common mode noise reduction circuit.

  In the circuit shown in FIG. 10, the inter-line capacitor 21c and the common mode coil 22b are deleted and a CT 24 and a common mode noise reduction circuit 25 are added to the circuit shown in FIG. As shown in FIG. 11, the CT 24 has an R, S, T, N-phase power supply line (input line) WR, WS, WT, WN connected to an annular magnetic core 26 made of a ferrite core like the common mode coil 22a. A common mode current detection winding (output line) WO is wound around the annular magnetic core 26 in the same manner as the R, S, T, and N phases.

  The R, S, T, and N-phase power lines WR, WS, WT, and WN are wound so that the magnetic flux in the magnetic core 26 is formed in the same direction when current flows in the same direction. Thus, the normal mode component is canceled. Therefore, only the common mode component appears as a magnetic flux in the magnetic core 26, and a change in the magnetic flux is detected as a common mode noise current in the common mode current detection winding WO.

  The common mode noise reduction circuit 25 is configured to flow a compensation current so that the common mode noise current detected by the CT 24 does not flow to the AC power supply 1 side.

  FIG. 12 is a block diagram of the common mode noise reduction circuit shown in FIG. The common mode reduction circuit 25 shown in FIG. 12 is provided with a DC voltage generation circuit including resistors r1 to r3, capacitors C1 to C2, diodes D1 to D3, and a PNP transistor Q1 (Patent Document 3).

The DC voltage generation circuit generates a DC voltage of about 160 V from an AC voltage having an effective value of 230 V between TN, for example. First, after the AC power supply voltage is applied, when the voltage is positive, current flows through a path of r3 → D1 → C1 → D2 → C2, and the capacitors C1 and C2 are charged. When the AC power supply voltage starts to decrease from the positive peak,
AC power supply voltage <(voltage across C1 + voltage across C2)
Thus, the diode D1 is reverse-biased and the transistor Q1 is turned on. In this case, a current path of C1 → Q1 → C2 → D3 is formed. In either case, the voltage at both ends of the capacitor C2 is always charged with a voltage that is about ½ of the peak value of the AC power supply voltage. By using the voltage between both ends of the capacitor C2 as an operating power supply for the common mode noise reduction circuit 25, a direct current voltage can be easily obtained with little loss and the number of parts.

  The common mode noise reduction circuit 25 is provided with an amplifier circuit including capacitors C3 to C5, resistors r4 and r5, an NPN transistor Q2, a PNP transistor Q3, and diodes D4 and D5 (Patent Document 4). The amplifier circuit supplies a compensation current for the common mode noise current detected by CT24 to the ground line E through the capacitor C5.

  First, when the common mode noise current flows to the output line WO of the CT 24 in the direction from P11 to P12, the base current flows to the transistor Q2, and the current flows through the path C2-> Q2-> P11-> P12-> C5 and C3. Flowing. The shunt ratio between the capacitor C5 and the capacitor C3 is determined by the current amplification factor hfe of the transistor Q2.

Current flowing in the capacitor C5: Current flowing in the capacitor C3 = hfe: 1
Thus, most of the current flows through the capacitor C5 under the condition of hfe >> 1.

  Further, when the common mode noise current flows in the CT24 output line WO in the direction from P12 to P11, the current flows to the base of the transistor Q3, and the ground line E → C5 → P12 → P11 → Q3 → N phase and Current flows through the path C4. The ratio of splitting into N phase and capacitor C4 is determined by hfe of transistor Q3.

Current flowing in N phase: Current flowing in C4 = hfe: 1
And almost all flows in the N phase under the condition of hfe >> 1.

Thus, the common mode noise current is canceled by the compensation current, and the common mode noise component flowing to the AC power supply side can be reduced.
Japanese Patent Laid-Open No. 9-266677 JP 2003-174777 A JP 2004-32885 A JP 2003-250270 A

  However, the conventional filter circuits described in Patent Documents 1 to 4 can reduce common mode noise, but cannot reduce normal mode noise. For this reason, a coil for normal mode must be added.

  The present invention provides an inverter device having a switching element and a noise reduction reactor and a noise reduction device that can reduce noise generated by a load without increasing the number of components and can be reduced in size and size.

  In order to solve the above problems, the present invention employs the following means. A noise reduction reactor which is inserted into a power supply line from a three-phase four-wire AC power supply according to the invention of claim 1 and reduces noise propagating to the power supply line. A first magnetic core that forms a closed magnetic path; a first winding that is provided corresponding to a power supply line from the three-phase four-wire AC power supply and is wound around the first magnetic core; a second winding; A third winding and a fourth winding are inserted into the through hole of the first magnetic core, and a second closed magnetic path is formed for each winding through a part of the first closed magnetic path of the first magnetic core. And a second magnetic core, and an insulator provided between the first magnetic core and the second magnetic core.

  According to a second aspect of the present invention, in the noise reduction reactor according to the first aspect, the second magnetic core includes a cross-shaped magnetic core, and the first winding, the second winding, and the third winding. And the fourth winding is wound around the first magnetic core so as to pass through four gaps formed when the cross-shaped second magnetic core is inserted into the through hole of the first magnetic core. It is characterized by being turned.

  The invention of claim 3 is a noise reduction device for reducing noise that is inserted into a power line from a three-phase four-wire AC power source and propagates to the power line, and is a common mode noise that flows from the power line to a ground line. A common mode noise current detector for detecting a current, and a common mode noise for supplying the common mode noise current detected by the common mode noise current detector to the ground line in a direction to cancel the common mode noise current. A reduction circuit and the noise reduction reactor according to claim 1 or 2 are provided.

  According to a fourth aspect of the present invention, in the noise reduction device according to the third aspect, the common mode noise reduction circuit is disposed closer to the three-phase four-wire AC power source than the common mode noise current detector, and the noise reduction is performed. The reactor is arranged on the three-phase four-wire AC power supply side with respect to the common mode noise reduction circuit.

  According to the noise reduction reactor of the present invention, magnetic flux due to the common mode noise current is generated in the first closed magnetic circuit of the first magnetic core. In the second magnetic core, a second closed magnetic path is formed for each winding through a part of the first closed magnetic path of the first magnetic core, and a magnetic flux due to normal mode noise current is generated in the second closed magnetic path for each winding. appear. A magnetic flux generated by a two-phase current passes through the second magnetic core, and the two-phase current has a phase difference of 120 degrees. For this reason, the magnetic flux by the normal mode noise current equivalent to the main current is generated in the second magnetic core. Therefore, common mode noise and normal mode noise can be reduced without increasing the number of parts, and the cost and size can be reduced.

  Moreover, since the noise reduction apparatus using the noise reduction reactor is configured, the same effect as that of the noise reduction reactor can be obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a noise reduction reactor and a noise reduction device of the present invention will be described in detail with reference to the drawings. In the following description, the noise reduction reactor is abbreviated as a reactor.

  FIG. 1 is a structural diagram of a reactor having a quadrangular magnetic core according to the first embodiment. A reactor La shown in FIG. 1 includes a rectangular magnetic core 5a made of a magnetic material such as ferrite, a cross-shaped magnetic core 6a made of a magnetic material such as ferrite, four insulators 7a, and four windings 10R. , 10S, 10T, 10N.

  The quadrangular magnetic core 5a corresponds to the first magnetic core of the present invention and is a magnetic core without a gap. The quadrangular magnetic core 5a has a quadrangular through hole 51 at the center and a closed magnetic circuit. The winding 10R, winding 10S, winding 10T and winding 10N (corresponding to the first winding, the second winding, the third winding and the fourth winding of the present invention) are three-phase four-wire AC power supplies. 1 is provided corresponding to the power lines 1 (symmetrical three-phase AC R-phase, S-phase, T-phase and N-phase which is the neutral point thereof) and is wound around the rectangular magnetic core 5a.

  The cross-shaped magnetic core 6a corresponds to the second magnetic core of the present invention, and is inserted into the through hole 51 of the rectangular magnetic core 5a with a predetermined gap and is square for each of the windings 10R, 10S, 10T, and 10N. A second closed magnetic path is formed through a part of the first closed magnetic path of the shaped magnetic core 5a. An insulator 7a is provided in a predetermined gap between the quadrangular magnetic core 5a and the protrusion 9a of the cross-shaped magnetic core 6a.

  The winding 10R, the winding 10S, the winding 10T, and the winding 10N pass through the four gaps 8a formed when the cross-shaped magnetic core 6a is inserted into the through hole 51 of the quadrangular magnetic core 5a. The same number of turns are wound around the rectangular magnetic core 5a.

  The winding 10R is connected between the port P1 and the port P2, the winding 10S is connected between the port P3 and the port P4, the winding 10T is connected between the port P5 and the port P6, and the winding 10N. Are connected between the port P7 and the port P8.

FIG. 2 is a diagram showing a magnetic flux generated by a normal mode current and a common mode current in the reactor of FIG. In the case of a three-phase four-wire AC power supply, the relationship of each current at the commercial frequency that is the main current is
Ir + Is + It + In = 0 (1)
It becomes.

  However, Ir is an R-phase current, Is is an S-phase current, It is a T-phase current, and In is an N-phase current. Each of the currents Ir, Is, It has a phase difference of 120 degrees, but the amplitude is not the same. Therefore, In = − (Ir + Is + It) ≠ 0. As a result, the magnetic flux generated in the rectangular magnetic core 5a by the phase current at the commercial frequency at any moment becomes 0, and the rectangular magnetic core 5a is not magnetically saturated.

  In addition, the magnetic flux generated by the high-frequency common mode noise current flowing through the grounding line E without the expression (1) is added to the magnetic flux generated by all the currents in the R, S, T, and N phases. As shown by a solid line, a magnetic flux φc due to a common mode noise current proportional to the total value of Ir + Is + It + In is generated in the rectangular magnetic core 5a. Since the magnetic flux φc due to the common mode noise current is much smaller than the main current at the commercial frequency, the rectangular magnetic core 5a without a gap is used.

On the other hand, in the cross-shaped magnetic core 6a, as shown by the dotted line in FIG. 2, the closed magnetic circuit (corresponding to the first closed magnetic circuit of the present invention) of the rectangular magnetic core 5a is provided for each of the windings 10R, 10S, 10T, and 10N. Four magnetic fluxes φ _R , φ _S , φ _T , and φ _N due to normal mode noise current are generated in the closed magnetic circuit formed through a part (corresponding to the second closed magnetic circuit of the present invention). Since two gaps are inserted in each closed magnetic path, the magnetic resistance is larger than that of the quadrangular magnetic core 5a.

Further, a magnetic flux generated by a two-phase current passes through each of the four protrusions 9a of the cross-shaped magnetic core 6a, as shown by the dotted lines in FIG. Since the two-phase current has a phase difference of 120 degrees, it is not canceled out. Therefore, magnetic fluxes φ _R , φ _S , φ _T , and φ _N are generated in the cross-shaped magnetic core 6a due to a large normal mode noise current equivalent to a large main current. Therefore, it is necessary to insert the gap GP so that the cross-shaped magnetic core 6a is not magnetically saturated.

  By adjusting the gap length of the gap GP, the magnetic flux density passing through the cross-shaped magnetic core 5a can be adjusted, and the inductance effective for the normal mode noise component can be adjusted. The four gaps GP have the same interval so that the inductance values of the respective phases are the same.

  In addition, the rectangular magnetic core 5a of the reactor La has two U-shaped magnetic cores, each of which has two U-shaped magnetic cores by inserting two bobbins each having a pre-wound winding around each short piece of the two U-shaped magnetic cores. It can be produced by bringing the core into close contact. Unlike the generally used rectangular magnetic core 5a, the wire can be wound around the bobbin by a machine without manually winding the wire, so that the manufacturing cost can be reduced.

Instead of the cross-shaped magnetic core 6a, four L-shaped magnetic cores (not shown) obtained by equally dividing the cross-shaped magnetic core 6a into four parts may be used. Also in this case, as shown by the dotted lines in FIG. 2, normal mode noise is generated in the closed magnetic circuit formed through a part of the closed magnetic circuit of the rectangular magnetic core 5a for each winding 10R, 10S, 10T, 10N. Four magnetic fluxes φ _R , φ _S , φ _T , and φ _N are generated by the current.

  When the four L-shaped magnetic cores and the cross-shaped magnetic core 6a are compared, the number of the cross-shaped magnetic core 6a is one, which is advantageous in that it is easy to manufacture. Further, since the two-phase current of the cross-shaped magnetic core 6a has a phase difference of 120 degrees, there is an advantage that it is not canceled and becomes zero.

  FIG. 3 is a structural diagram of a reactor having a quadrangular magnetic core according to the second embodiment. The reactor Lb of Example 2 shown in FIG. 3 arrange | positions the insulator 7b over the whole internal peripheral surface of the square-shaped magnetic core 5a with respect to the reactor La of Example 1 shown in FIG. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to the same portions, and detailed descriptions thereof are omitted.

  Even if it is the reactor Lb of such Example 2, the effect similar to the reactor La of Example 1 is acquired.

  FIG. 4 is a structural diagram of a reactor having an annular magnetic core according to the third embodiment. A reactor Lc shown in FIG. 4 includes an annular magnetic core 5c made of a magnetic material such as ferrite, a cross-shaped magnetic core 6c made of a magnetic material such as ferrite, an annular insulator 7c, and four windings 10R and 10S. , 10T, 10N.

  An annular insulator 7c is provided on the inner peripheral surface of the annular magnetic core 5c, and a cross-shaped magnetic core 6c is provided on the inner peripheral surface of the annular insulator 7c. Four windings 10R, 10S, 10T, and 10N are wound around the gap 8c between the annular insulator 7c and the cross-shaped magnetic core 6c.

  Even if it is the reactor Lc of such Example 3, the effect similar to the reactor La of Example 1 is acquired.

  FIG. 5 is a structural diagram of a reactor having a quadrangular magnetic core according to the fourth embodiment. The reactor Ld shown in FIG. 5 differs from the reactor La of the first embodiment shown in FIG. 1 in a quadrangular magnetic core 5d and an I-shaped magnetic core 6d.

  The quadrangular magnetic core 5d has two protrusions 9d formed at positions facing the magnetic core. The I-shaped magnetic core 6d is inserted into the through hole 51 of the quadrangular magnetic core 5d with a predetermined gap, and the first closed magnetic circuit of the quadrangular magnetic core 5d is provided for each winding 10R, 10S, 10T, 10N. A second closed magnetic circuit is formed through a part. An insulator 7a is provided in a predetermined gap between the quadrangular magnetic core 5d and the I-shaped magnetic core 6d.

  The winding 10R, the winding 10S, the winding 10T, and the winding 10N pass through the four gaps 8d that are formed when the I-shaped magnetic core 6d is inserted into the through hole 51 of the quadrangular magnetic core 5d. Thus, the same number of turns are wound around the rectangular magnetic core 5d.

  According to the reactor Ld of the fourth embodiment, in the I-shaped magnetic core 6d, the windings 10R, 10S, 10T, and 10N have a closed magnetic circuit formed through a part of the closed magnetic circuit of the rectangular magnetic core 5d. Four magnetic fluxes are generated by the normal mode noise current. Since two gaps are inserted in each closed magnetic path, the magnetic resistance is larger than that of the quadrangular magnetic core 5d.

  Further, the magnetic flux generated by the two-phase current passes through the I-shaped magnetic core 6d. Since the two-phase current has a phase difference of 120 degrees, it is not canceled out. For this reason, the I-shaped magnetic core 6d generates a magnetic flux due to a large normal mode noise current equivalent to a large main current. Therefore, it is necessary to insert the gap GP so that the I-shaped magnetic core 6d is not magnetically saturated.

  Thus, even if it is the reactor Ld of Example 4, the effect similar to the reactor La of Example 1 is acquired.

  FIG. 6 is a configuration diagram of the noise reduction apparatus according to the fifth embodiment. The filter circuit 2c, which is the noise reduction device of the fifth embodiment shown in FIG. 6, detects the common mode noise current flowing from the power line to the ground line E, between the line capacitors 21a and 21b, the reactor L, the line-ground capacitor 23, and the ground line E. CT 24 and a common mode noise reduction circuit 25 that supplies the common mode noise current detected by CT 24 to the ground line E in a direction to cancel the common mode noise current.

  That is, in the noise reduction device of the fifth embodiment shown in FIG. 6, the common mode coil 22a of the noise reduction device shown in FIG. 10 is replaced with a reactor L (reactor La shown in FIG. 1, reactor Lb shown in FIG. 3, or shown in FIG. The reactor Lc is replaced with the reactor Ld) shown in FIG. The inter-line capacitors 21a and 21b are connected to the previous stage of the CT 24.

  Further, the common mode noise reduction circuit 25 is arranged closer to the three-phase four-wire AC power supply 1 than the CT 24, and the reactor L is arranged closer to the three-phase four-wire AC power supply 1 than the common mode noise reduction circuit 25. The

  According to such a configuration, since the noise reduction reactor L is used in the noise reduction device, the same effects as those of the first to fourth embodiments can be obtained. In addition, since the amplification factor of the common mode noise reduction circuit 25 can be reduced and oscillation is eliminated, the circuit can be stabilized.

  FIG. 7 is a configuration diagram of the noise reduction apparatus according to the sixth embodiment. The noise reduction apparatus according to the sixth embodiment illustrated in FIG. 7 is characterized in that the connection position of the inter-line capacitor 21b is the latter stage of the CT 24 with respect to the noise reduction apparatus according to the sixth embodiment illustrated in FIG.

  According to such a configuration, since the noise reduction reactor L is used in the noise reduction device, the same effects as those of the first to fourth embodiments can be obtained. In addition, since the amplification factor of the common mode noise reduction circuit 25 can be reduced and oscillation is eliminated, the circuit can be stabilized.

  The present invention can be applied to a motor driven by a three-phase AC power source.

1 is a structural diagram of a reactor having a quadrangular magnetic core of Example 1. FIG. It is a figure which shows the magnetic flux by a normal mode electric current and a common mode electric current in the reactor of FIG. 6 is a structural diagram of a reactor having a quadrangular magnetic core of Example 2. FIG. 6 is a structural diagram of a reactor having an annular magnetic core according to Embodiment 3. FIG. 6 is a structural diagram of a reactor having a quadrangular magnetic core according to Embodiment 4. FIG. It is a block diagram of the noise reduction apparatus of Example 5. It is a block diagram of the noise reduction apparatus of Example 6. It is a connection diagram of a conventional motor. It is the conventional filter circuit diagram comprised with the capacitor | condenser and the reactor. It is the conventional filter circuit diagram provided with the common mode noise current detector (CT) and the common mode noise reduction circuit. It is a block diagram of the common mode noise current detector shown in FIG. It is a block diagram of the common mode noise reduction circuit shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2, 2a-2d Filter circuit 3 Inverter apparatus 4 Motor 5a, 5d Square-shaped magnetic core 5c, 26 Annular magnetic core 6a, 6c Cross-shaped magnetic core 6d I-shaped magnetic core 7a, 7b, 7c Insulator 8a, 8c, 8d Air gaps 9a, 9c, 9d Protrusions 21a, 21b, 21c Line-to-line capacitors 22a, 22b Common mode coil 23 Line-to-ground capacitor 24 Common mode noise current detector (CT)
25 Common mode noise reduction circuit 50 Side leg 51 Through hole L, La to Ld Reactor C11 to C23 Capacitor L11 to L18 Coil P1 to P8, P11 to P20 Port

Claims (4)

A noise reduction reactor that is inserted into a power line from a three-phase four-wire AC power source and reduces noise propagating to the power line,
A first magnetic core having a through hole in the center and forming a first closed magnetic path;
A first winding, a second winding, a third winding, and a fourth winding that are provided corresponding to a power supply line from the three-phase four-wire AC power supply and are wound around the first magnetic core;
A second magnetic core inserted into the through hole of the first magnetic core and forming a second closed magnetic path through a part of the first closed magnetic path of the first magnetic core for each winding;
An insulator provided between the first magnetic core and the second magnetic core;
The reactor for noise reduction characterized by comprising. The second magnetic core comprises a cross-shaped magnetic core,
The first winding, the second winding, the third winding, and the fourth winding are formed when the cross-shaped second magnetic core is inserted into a through hole of the first magnetic core. The noise reduction reactor according to claim 1, wherein the first magnetic core is wound so as to pass through the four gaps. A noise reduction device that is inserted into a power supply line from a three-phase four-wire AC power supply and reduces noise propagating to the power supply line,
A common mode noise current detector for detecting a common mode noise current flowing from the power line to the ground line;
A common mode noise reduction circuit that supplies the common mode noise current detected by the common mode noise current detector to the ground line in a direction that cancels the common mode noise current;
The noise-reducing reactor according to claim 1 or 2,
A noise reduction device comprising: The common mode noise reduction circuit is disposed on the three-phase four-wire AC power supply side than the common mode noise current detector,
The noise reduction device according to claim 3, wherein the noise reduction reactor is arranged closer to the three-phase four-wire AC power supply side than the common mode noise reduction circuit.

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