JP2001099475A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent switching noise of a switching element or the like, which is transferred to a metallic chassis through a stray capacity between a reactor and the metallic chassis, from being radiated through a pipeline and the like. SOLUTION: Noise, propagated from a switching element 23 or the like to a reactor 24, a stray capacity 23 and a metallic chassis 34, can be prevented by a ferrite core 35, inserted into the connecting line 36 of the reactor 24 through a common mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner having an active filter.

[0002]

2. Description of the Related Art In recent years, a booster type active filter having a switching element has been mounted on an air conditioner for the purpose of improving a power factor, increasing efficiency, increasing the maximum output, and the like. Speeding up has been done.

Hereinafter, a conventional air conditioner will be described with reference to FIG.

[0004] As shown in FIG. 4, a rectifier 2 for rectifying an AC power supply 1 to DC, a switching element 3, a reactor 4,
An active filter 10 including a diode 5, a first voltage detecting means 6, a current detecting means 7, a second voltage detecting means 8, and a control circuit 9, a smoothing capacitor 11, and a load 12
, A noise reduction noise filter 13, and a metal chassis 14.

Hereinafter, the operation will be described. When the switching element 3 is off, the AC power supply 1 is rectified by the rectifier 2, and a current flows to the smoothing capacitor 11 via the reactor 4 and the diode 5.

When the switching element 3 is on,
A current flows from the rectifier 2 to the reactor 4 and the switching element 3.

Then, the switching element 3 is turned on and off at a frequency of 20 kHz by the control circuit 9, and the voltage of the smoothing capacitor 11 detected by the second voltage detecting means 8 is controlled to a desired voltage.

Further, the voltage / current detected by the first voltage detecting means 6 and the current detecting means 7 are calculated, and the current flowing through the reactor 4, that is, the current of the AC power supply 1 is controlled so as to be substantially sinusoidal. This improves power factor and reduces harmonic current. Further, a noise filter 13 is inserted to prevent switching noise of the switching element 3 and the like from being superimposed on the AC power supply 1.

The reactor 4 is screwed to a metal chassis 14 of the air conditioner.

[0010]

However, in the above-mentioned conventional configuration, the superposition of noise on the AC power supply 1 is prevented by the noise filter 13, but the superposition of noise on the AC power supply 1 is prevented through the stray capacitance 15 between the reactor 4 and the metal chassis 14. There is a problem that switching noise of the switching element 3 and the like propagates to the metal chassis 14 having the same potential as the ground, and is radiated through a pipe fixed to the metal chassis 14 with screws or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to prevent the propagation of noise from a reactor to a metal chassis and to reduce the loss of the reactor in an air conditioner.

[0012]

According to a first aspect of the present invention, there is provided an active filter including a reactor, a switching element, and the like, wherein the reactor has a same potential as a ground. Touch the chassis,
Further, a common mode ferrite core is inserted into a connection line connected to the reactor.

[0013] Further, the invention described in claim 2 is approximately 15 k
An active filter that operates at a frequency in the range of 25 kHz to 25 kHz, and a reactor for an active filter in which a plurality of strands each having an insulating film and having a diameter of 0.9 mm or less are twisted to form a winding. is there.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

The invention as set forth in claim 1 has an active filter 30 including a reactor 24, a switching element 23 and the like as shown in FIG. 1, and the reactor 24 is connected to the ground as shown in FIG. A connection line 36 for contacting a metal chassis 34 of potential and connecting to the reactor 24;
In this configuration, a common mode ferrite core 35 is inserted. With this configuration, the propagation of noise from the reactor 24 to the metal chassis 34 can be prevented.

Further, the invention described in claim 2 is approximately 15
As shown in FIG. 3, an active filter 30 that operates at a frequency in the range of 25 kHz to 25 kHz, and as shown in FIG. The active filter reactor 24 has a configuration as described above. With this configuration, it is possible to prevent a problem that the high-frequency ripple current of 15 kHz to 25 kHz is concentrated on the surface of the copper wire due to the skin effect and almost no current flows in the center of the copper wire.

[0017]

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

(Embodiment 1) First, Embodiment 1 of the present invention will be described with reference to FIGS. As shown in FIG.
A rectifier 22 for rectifying the AC power supply 21 to DC, a switching element 23, a reactor 24, a diode 25,
An active filter 30 comprising a voltage detecting means 26, a current detecting means 27, a second voltage detecting means 28, and a control circuit 29; a smoothing capacitor 31; a load 32; a noise filter 33 for reducing noise; And a ferrite core 35.

Next, the operation and action will be described. When the switching element 23 is off, the AC power supply 2
1 is rectified by a rectifier 22, a reactor 24, a diode 2
5, a current flows through the smoothing capacitor 31. When the switching element 23 is on, a current flows from the rectifier 22 to the reactor 24 and the switching element 23.

The control circuit 29 drives the switching element 23 on and off at a frequency of 20 kHz,
The voltage of the smoothing capacitor 31 detected by the voltage detecting means 28 is controlled to a desired voltage.

The voltage and current detected by the first voltage detecting means 26 and the current detecting means 27 are calculated by a microcomputer (not shown) constituting the control circuit 29, and the current flowing through the reactor 24, that is, By controlling the current of the AC power supply 21 to have a substantially sinusoidal shape, the power factor is improved and the harmonic current is reduced.

As shown in FIG. 2, a ferrite core 35 is inserted into a connection line 36 from the connection terminal 24a of the reactor 24 to A and B shown in FIG.

Further, the reactor 24 is brought into contact with a metal chassis 34 having the same potential as the ground, and is fixed with screws 37. As a result, a stray capacitance 38 exists between the winding 24 c or the core 24 d of the reactor 24 and the metal chassis 34.

The switching noise of the switching element 23 (FIG. 1) and the noise at the time of recovery of the diode 25 (FIG. 1) are transmitted not only through the point B in FIG. 1 but also through the control circuit 29 and the first voltage detecting means 26. Although propagated to point A, as shown in FIG. 2, both connection wires 36 of the reactor 24 are inserted in a common mode inserted into the hole 35a of the ferrite core 35, so that the reactor 24, Noise propagation to the stray capacitance 38 and the metal chassis 34 can be prevented. As a result, noise radiated from pipes or the like can be prevented.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIGS.

In FIG. 3 (a), a winding 24c of the reactor 24 is composed of a stranded wire 41 obtained by twisting a wire 40 made of an insulating copper wire (polyurethane copper wire in this embodiment) having a diameter of 0.5 mm. As shown in FIG. 3B, this is a configuration wound up around a core 24d.

The operation and operation will be described below.

The operation of the active filter 30 is the same as that of the first embodiment, and the description is omitted. Switching element 23
Is 20k outside the audible range and with small switching loss
On / off operation is performed at a frequency of Hz, and a high-frequency ripple current of 20 kHz is superimposed on the reactor 24.

Here, the material of the wire 40 is copper, and the penetration depth of the high-frequency ripple current at a frequency of 20 kHz is 0.46 mm due to the skin effect.
The current concentrates in an area within 6 mm.

Therefore, almost no current flows in a region 0.46 mm or more from the surface, but in this embodiment, the polyurethane copper having a diameter of 0.9 mm has a diameter of the wire 40 of the reactor 24 substantially equal to the penetration depth at 20 kHz. Wire 4 consisting of wires
Since the stranded wire 41 is used to form the stranded wire 41, current flows in the entire cross-sectional area of the stranded wire 41, and the resistance value does not increase even with respect to the high-frequency ripple current, so that the loss can be reduced.

The penetration depth varies depending on the metal material, and is calculated by a calculation formula based on the resistivity, relative permeability and frequency of the metal. When the wire 40 is copper, the penetration depth at a frequency of 20 kHz is used. The value of the depth is a known value of 0.46 mm.

[0032]

As apparent from the above embodiment, the invention according to claim 1 has an active filter including a reactor, a switching element, and the like, and the reactor is brought into contact with a metal chassis having the same potential as the ground, In addition, since the ferrite core is inserted into the connection line connected to the reactor in a common mode, the propagation of noise from the switching element to the reactor, the stray capacitance, and the metal chassis can be prevented. Noise radiated from the device can be prevented.

[0033] The invention described in claim 2 is approximately 15
By having an active filter that operates at a frequency in the range of 25 kHz to 25 kHz, and a reactor for an active filter in which a plurality of strands each having a diameter of 0.9 mm or less and having an insulating film are twisted and wound as a winding. Even when the active filter is operated outside the audible range and at the operating frequency of 20 kHz, which is the minimum switching noise, the current flows through the entire area of the cross section of the stranded wire 41, and the resistance value with respect to the high-frequency ripple current is also small. The loss can be reduced without increasing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an active filter of an air conditioner showing an embodiment of the present invention.

FIG. 2 is a perspective view of a main part showing a configuration of an active filter of the present invention.

FIG. 3 is a cross-sectional perspective view of a main part showing a configuration of a winding of a reactor showing another embodiment of the present invention.

FIG. 4 is a circuit diagram of an active filter of an air conditioner showing a conventional example.

[Explanation of symbols]

 24 Reactor 30 Active filter 34 Metal chassis 35 Ferrite core 36 Connection wire 40 Element wire 41 Twisted wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takato Ueshima 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Yuji Tani 1006 Kadoma Kadoma, Kadoma City Osaka Prefecture F-term (reference) 3L061 BA07

Claims (2)

[Claims] 1. An active filter comprising at least a reactor, a switching element and the like, wherein the reactor is brought into contact with a metal chassis having the same potential as the ground, and a ferrite core is inserted in a common mode into a connection line connected to the reactor. Air conditioner. 2. An active filter operating at a frequency in a range of approximately 15 kHz to 25 kHz, and an active filter reactor having a winding of a stranded wire having a plurality of strands having a diameter of 0.9 mm or less and having an insulating film wound thereon. Having an air conditioner.