JPH11146557A - Leakage current suppress circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce leakage current which flows via a housing and clear a regulation value easily, even if new coolant is used. SOLUTION: A current suppress circuir 20, which consists of two Zener diodes 25a and 25b connected to each other bidirectionally, is provided between the connection point of two Y-capacitors 22 in a common mode filter and a housing A so as to make a current flow, only when a voltage higher than a predetermined voltage is applied so as to suppress a current flowing through the housing A. Further, a phase regulating circuit 26 is formed by setting the capacitances of the Y-capacitors 22 and the inductances of common mode reactors 23 so that optimum conditions are realized, including making the direction of the current opposite to the direction of a current flowing into the housing from another path. With this constitution, a leakage current flowing into the ground from the housing A can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage current suppression circuit capable of suppressing a leakage current generated in a device through a plurality of paths into a housing and then flowing to the ground.

[0002]

2. Description of the Related Art Compressors used in air-conditioning air and the like today are composed of a compression mechanism, a motor for applying a driving force to the compression mechanism, and the like, which are housed in a case. The compression mechanism receives the driving force from the motor, and the compression mechanism sucks and compresses the refrigerant.

[0003] In recent years, rotary compressors and scroll compressors have become the mainstream of such compressors. In such compressors, the compressed refrigerant is once discharged into a case (the atmosphere inside the case and the atmosphere inside the case). ), And the structure is generally discharged to the outside through a pipe fixed to the case.
Therefore, since the inside of the case is filled with the compressed high-pressure refrigerant, the case is a closed case.

[0004] Such a motor housed in a closed case includes a DC motor and an AC motor, but an inverter-driven DC motor is used from the viewpoints of noiseless driving, easy control, and miniaturization of the device. A brushless DC motor that does not require brush repair or the like because of its closed case is used.

FIG. 3 shows an example of a drive circuit for performing such inverter drive. The driving circuit includes a noise filter circuit 11 for attenuating common mode noise, an active filter circuit 12, and a three-phase inverter circuit 13 as main circuits. The active filter circuit 12 boosts an AC voltage to a DC voltage by a chopper (the chopper cycle is For example, 30
kHz) while smoothing the three-phase inverter circuit 1
Numeral 3 switches the DC voltage from the active filter circuit 12 at a predetermined cycle (for example, 5 kHz) to supply power to the DC motor M. The symbol k indicates a sealed case, and the symbol A indicates a housing for air-conditioned air or the like.

[0006]

However, in the above configuration, a refrigerant such as R-22 (hereinafter referred to as an old refrigerant), which has recently become a cause of ozone hole generation, has been replaced by a refrigerant such as HFC (hereinafter referred to as a new refrigerant). Switching to refrigerant) has the problem of increasing the leakage current.

Normally, an air conditioner or the like provided with a compressor is grounded from the viewpoint of safety such as electric shock prevention, and an electronic circuit such as a drive circuit is grounded from the viewpoint of stable operation. In this specification, a compressor and an electronic circuit are collectively called an electric device.

[0008] As described above, a metal pipe (not shown) is fixed to the sealed case k of the compressor by welding or the like, and the pipe has electrical contact with the housing A. It is grounded via A.

In such a situation, the three-phase inverter circuit 13
When the intermittent DC current that has been switched at high speed is supplied to the DC motor M, the DC current flows, and the power lines and windings (the stator of the DC motor M) in the sealed case k pass through the new refrigerant. Capacitively coupled with the closed case k. The current flowing by such capacitive coupling is high-frequency noise and becomes a leakage current.

[0010] Such a capacitive coupling has also occurred in a compressor using an old refrigerant, but the new refrigerant has a lower resistivity and a higher dielectric constant than the old refrigerant, so that the capacitive coupling becomes large and the leakage current increases. It is difficult to clear the legal regulation value (1 mA).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a leakage current suppressing circuit which can easily reduce the leakage current with a simple configuration even when a new refrigerant is used, so that the regulation value can be cleared. And

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that noise generated in a device equipped with electric equipment is transmitted to at least two or more paths to a housing of the device. In a leakage current suppression circuit for suppressing a leakage current flowing from the housing to the ground via a ground line, at least one of a plurality of paths is provided with a current suppression circuit for suppressing a current flowing through the path. Thereby, the leakage current flowing through the ground line is suppressed.

According to a second aspect of the present invention, at least one of a plurality of paths is provided with a phase adjusting circuit for controlling a phase of a current flowing through the path. The phase of the current flowing into the housing via a plurality of paths is changed to cause mutual interference, thereby reducing the current flowing from the housing to the ground.

According to a third aspect of the present invention, at least one of the current suppressing circuit and the phase adjusting circuit comprises a Zener diode. Then, a current of a voltage lower than the Zener voltage is prevented from flowing into the housing to function as a current suppressing circuit, and a junction capacitance of the Zener diode changes a phase of a current flowing through the Zener diode to function as a phase adjustment circuit. It is characterized by doing so.

According to a fourth aspect of the present invention, there is provided a common circuit comprising two capacitors connected in series so as to short-circuit an AC line for supplying power to an electric device of the apparatus, and a coil connected to the AC line. In the mode filter, a Zener diode is connected bidirectionally between the connection point of the two capacitors and the housing to form a current suppression circuit, and the capacitance and inductance are set so that the two capacitors and the coil form a phase adjustment circuit. It is characterized by having been set.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals are used for the same components as those in the related art, and description thereof is omitted as appropriate.

Prior to the description of the embodiment, the principle of operation of the present invention will be briefly described. In a circuit as shown in FIG.
The sealed case k of the compressor is connected to the housing A, and the noise filter circuit 11 is connected to the housing A. Therefore, a current path flowing through the line from the noise filter circuit 11 and a current path from the sealed case k exist in the housing A.

The currents flowing through the two paths are noises generated in the apparatus and are generally switching frequency noises. Therefore, the currents merge in the housing A and become leakage currents, which interfere when flowing to the ground. Therefore, it is considered that when these currents are in opposite phases, they interfere with each other and the leakage current is minimized.

It is also considered that shutting off the two currents more directly is effective in reducing the leakage current. However, if the current from the noise filter circuit 11 is completely cut off,
Since the noise filter circuit 11 does not function and EMI noise such as a noise terminal voltage increases, it is considered necessary to supply a current to such an extent that the function of the noise filter circuit 11 can be maintained.

FIG. 1 is a circuit diagram of a drive circuit 10 having a current suppression circuit 20 configured based on the above considerations. The drive circuit 10 includes a noise filter circuit 11, an active filter circuit 12, a three-phase inverter circuit 13, It comprises a current suppression circuit 20 according to the present invention.

The noise filter circuit 11 includes an X capacitor (capacitor connected between AC lines) 21, a Y capacitor (two capacitors connected in series between AC lines) 22,
The common mode reactor coil 23 provided between them has a main configuration.

The current suppressing circuit 20 has zener diodes 25a and 25b bidirectionally connected.
It is provided between the connection point of the capacitor 22 and the housing A.

In the above description and the following description, the current path flowing into the housing A is limited to two paths, that is, a path from the noise filter circuit 11 and a path from the sealed case k. I do. However, it is added that the generality of the present invention is not lost even in such a case.

FIG. 2 shows the measurement results of the leakage current when the Zener voltage of the Zener diodes 25a and 25b in the current suppressing circuit 20 is changed in the above configuration. From the figure, it can be seen that the Zener voltage is a specific voltage value (about 20 V in FIG. 2).
It can be seen that the leakage current has a minimum value at the time.

In FIG. 2, the unit of the leakage current is voltage. This is because the value measured by the leakage current measuring device according to the leakage current measurement standard is shown as it is. In the leakage current measuring device, when the measurement voltage is 1 V, the leakage current is 1 mA, and the regulated value of the leakage current is 1 m.
A.

Changing the Zener voltage in this way has the following meaning. That is, in the measurement in FIG. 2, the Zener voltage is changed by exchanging the Zener diodes 25a and 25b.

The Zener diodes 25a and 25b are formed by high-concentration PN junctions, and the Zener voltage changes by changing the concentration. However, when the concentration of the PN junction is changed (when the Zener voltage is changed), the junction capacitance also changes.

Therefore, the measurement results shown in FIG. 2 are considered to be the effect of changing the zener voltage and the effect of changing the junction capacitance.

The effect of changing the zener voltage suppresses the current flowing from the noise filter circuit 11 to the housing A while maintaining the function of the noise filter circuit 11. The effect of changing the junction capacitance changes the phase of the two currents flowing into the housing A. Then, it is determined that a minimum value has occurred in the leakage current as a result of these.

In a real device such as an air conditioner, the phase of the current flowing into the housing A is not always substantially opposite due to the junction capacitance of the Zener diodes 25a and 25b.

In such a case, it is preferable to provide a separate phase adjusting circuit so that the ground line provided actually has the opposite phase.

Of course, the noise filter circuit 11 shown in FIG.
Of the component values such as the capacity of the Y-capacitor 22 and the inductance of the common-mode reactor coil 23, which are used in the above-described method, including the configuration in which the phase of the current flowing into the housing A is made substantially opposite to that of the component A. It is also possible to use

In this case, since the Y capacitor 22 and the common mode reactor coil 23 function as the phase adjustment circuit 26, there is an advantage that it is not necessary to provide an independent circuit.

[0034]

As described above, according to the first aspect of the present invention, when noise generated in a device equipped with an electric device flows into a housing of the device via at least two or more paths, Since at least one path is provided with a current suppression circuit or a phase adjustment circuit for suppressing a current flowing through the path, it is possible to easily suppress a leakage current flowing through the ground line.

According to the second aspect of the present invention, at least one of the plurality of paths is provided with the phase adjustment circuit for controlling the phase of the current flowing through the path. The leakage current flowing from the housing to the ground due to the interference of the flowing current can be reduced.

According to the third aspect of the present invention, at least one of the current suppressing circuit and the phase adjusting circuit is constituted by a Zener diode, so that a current having a voltage lower than the Zener voltage is prevented from flowing into the housing. In addition to functioning, the phase of the current flowing through the Zener diode is changed by the junction capacitance of the Zener diode to function as a phase adjustment circuit, thereby making it possible to reduce leakage current.

According to a fourth aspect of the present invention, two capacitors connected in series so as to short-circuit an AC line for supplying power to the electric equipment of the apparatus are connected, and a coil is connected to each AC line. In a common mode filter, a Zener diode is connected bidirectionally between the connection point of two capacitors and the housing to form a current suppression circuit, and the capacitance and inductance so that the two capacitors and the coil form a phase adjustment circuit. Is set, it is possible to easily and inexpensively suppress the leakage current.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram including a leakage current suppression circuit according to the present invention.

FIG. 2 is a diagram showing a measurement result of a leakage current when a Zener voltage is changed.

FIG. 3 is a drive circuit diagram applied to the description of the conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Drive circuit 11 Noise filter circuit 20 Current suppression circuit 22 Y capacitor 23 Common mode reactor coil 25a, 25b Zener diode 26 Phase adjustment circuit M DC motor k Closed case A Housing

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[Procedure amendment]

[Submission date] February 25, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

Nowadays, compressor used in an air conditioner or the like is constituted by a motor for providing a driving force to the compression mechanism and the compression mechanism, they are housed in the case. The compression mechanism receives the driving force from the motor, and the compression mechanism sucks and compresses the refrigerant.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

FIG. 3 shows an example of a drive circuit for performing such inverter drive. The driving circuit includes a noise filter circuit 11 for attenuating common mode noise, an active filter circuit 12, and a three-phase inverter circuit 13 as main circuits. The active filter circuit 12 boosts an AC voltage to a DC voltage by a chopper (the chopper cycle is For example, 30
kHz) while smoothing the three-phase inverter circuit 1
Numeral 3 switches the DC voltage from the active filter circuit 12 at a predetermined cycle (for example, 5 kHz) to supply power to the DC motor M. Reference numeral k denotes a sealed case, reference symbol A denotes a housing of the air conditioner or the like.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007] Usually, air conditioner or the like compressor is disposed in the housing from the viewpoint of safety such as prevention electric shock is grounded.
In this specification, a compressor and an electronic circuit are collectively called an electric device.

Claims (4)

[Claims] 1. A leakage current which suppresses a leakage current generated in an apparatus provided with an electric device through at least two paths to a housing of the apparatus and flowing from the housing to the ground via a ground line. In the suppression circuit, a current suppression circuit for suppressing a current flowing through at least one of the plurality of paths is provided. 2. The leakage current suppression circuit according to claim 1, wherein at least one of the plurality of paths is provided with a phase adjustment circuit for controlling a phase of a current flowing through the path. 3. The leakage current suppression circuit according to claim 1, wherein at least one of said current suppression circuit and said phase adjustment circuit comprises a Zener diode. 4. A common mode filter in which two capacitors connected in series to an AC line for supplying electric power to the electric equipment of the device and a coil is connected to the AC line are provided. The Zener diode is bidirectionally connected between the connection point and the housing to form the current suppression circuit, and the capacitance and inductance are set so that the two capacitors and the coil form the phase adjustment circuit. The leakage current suppressing circuit according to claim 3, wherein: