JP2001136658A - Grounding characteristic converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grounding characteristic converting device which can select the object of grounding and the pattern of grounding easily so as to reduce the noise flowing into an electric apparatus. SOLUTION: The series circuit of capacitors C1 and C2 is connected between both terminals of the output side of an AC power supply ACV. The potential of the connection point of the capacitors C1 and C2 is the arithmetical mean of the potentials of both terminals on the output side of the AC power supply ACV. If the acom contact and a1 contact of a switch SW1 and the bcom contact and b1 contact of a switch SW2 are closed, the flow of common mode noise generated by the AC power supply ACV into a load Z is blocked. If the acom contact and a2 contact of the switch SW1 are closed, the common mode noise is consumed by a resistor R1. If the acom contact and a3 contact of the switch SW1 and the bcom contact and b3 contact of the switch SW2 are closed, the load Z is not influeneced by the noise of the ground side of the AC power supply ACV. If the bcom contact and b2 contact of the switch SW2 are closed, the common mode noise is consumed by a resistor R2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grounding characteristic converter for changing a grounding state of a power supply or an electric device.

[0002]

2. Description of the Related Art In general, when using electric equipment, it is necessary to secure the electric equipment (that is, to prevent danger to the human body or the like due to earth leakage, or to prevent the destruction of the electric equipment due to lightning, etc.), or In order to prevent noise from flowing into the electric device, a predetermined node of a circuit constituting the electric device is grounded to a conductor outside the electric device.

[0003]

However, when the potential of a ground terminal (for example, a ground terminal provided in an outlet of a commercial power supply) included in a power supply fluctuates due to noise, electric equipment is connected to the ground terminal. When the grounding is performed by connecting the power supply, there is a problem that noise that changes the potential of the ground terminal of the power supply flows into the electric device.

There is also a problem that a current path flowing from the above-described predetermined node of the electric device to the external conductor has a reactance component, and the current path resonates with noise to enhance the noise. Further, when the current path flowing from the above-described predetermined node to the external conductor forms a closed loop, a noise drop circulating in the closed loop causes a voltage drop in the closed loop, and a noise voltage is generated in the current path, There is also a problem that the potential of the above-mentioned predetermined node becomes unstable.

In order to solve these problems, conventionally, each time a failure due to noise occurs in an electric device, an external conductor to be grounded and a manner of grounding are individually determined and grounded. Work was underway to change the target and the mode of grounding. However, it is difficult to appropriately select a target to be grounded and a mode of grounding, and construction for changing the target of grounding and the mode of grounding is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a grounding characteristic conversion for enabling easy selection of a grounding target and a grounding mode so as to reduce the flow of noise into electric equipment. It is intended to provide a device.

[0007]

To achieve the above object, a grounding characteristic converter according to a first aspect of the present invention provides a single-phase AC power supplied from an external power source having a first grounding terminal. An average potential generating means for generating, at a first node provided therein, a potential corresponding to an arithmetic average of the potentials of a pair of transmission paths for transmitting to an external load; and an average potential generating means connected to the first ground terminal. A second node, a first resistor having one end connected to the first ground end, a third node connected to the other end of the first resistor, and , A first switch connecting the first node to one of the second and third nodes.

According to such a ground characteristic converter, when the common mode noise applied to each transmission line in almost the same phase is bypassed, the first node and the second node are connected to each other, and the common mode noise is connected. When you consume
By performing an operation such as connection between the third node and the third node, the object to be grounded and the mode of grounding are easily selected, and the inflow of noise into the electric device is reduced.

[0009] The ground characteristic conversion device may further include a fourth node connected to an external field ground that is not substantially connected to the first ground terminal. The switch may connect the first node to one of the second to fourth nodes in accordance with an operation of an operator. Thus, even when the potential of the first ground terminal is likely to fluctuate, the potential of the first ground terminal is stabilized.

[0010] The load may have a second ground terminal. In this case, the ground characteristic conversion device may include a fifth node connected to the second ground terminal, and one end connected to the first ground terminal. A second resistor connected to a ground end, a sixth node connected to the other end of the second resistor, and the fifth node, the second node being connected to the second node according to an operation of an operator. A second switch connected to one of the fourth and sixth nodes. According to such a grounding characteristic converter, when the potential at the ground terminal of the load is fixed to the arithmetic mean of the potentials of the respective transmission paths, the fifth node and the second node are connected to each other so that the potential is substantially in phase with the load. When the applied noise is consumed, the fifth node is connected to the sixth node, and the potential of the ground terminal of the power source is changed to the field ground in order to prevent the fluctuation of the potential of the ground terminal of the power source from affecting the load. When the potential is fixed to the potential of the fifth node and the fourth node, the operation of connecting the fifth node to the fourth node, etc., is performed, so that the grounding target and the mode of the grounding are easily selected. It is reduced.

The average potential generating means includes, for example, a first capacitor having one end connected to one of the pair of transmission lines and the other end connected to the first node, and one end connected to the pair of transmission lines. And a second capacitor having the other end connected to the first node and having a capacitance substantially equal to that of the first capacitor. At the first node.

Further, the ground characteristic conversion device according to a second aspect of the present invention has a first node connected to a first ground terminal of an external power source, and one end connected to the first ground terminal. A first resistor connected thereto, a second node connected to the other end of the first resistor, and a single-phase AC power supplied by the external power source according to an operation of an operator. A first switch that connects an external node that generates a potential corresponding to an arithmetic average of potentials of the pair of transmission paths for transmitting to the load to one of the first and second nodes; , Is provided.

According to such a ground characteristic converter, when the common mode noise applied to each transmission line in almost the same phase is to be bypassed, an external node is connected to the first node, and the common mode noise is reduced. When the power is consumed, an operation such as connection between the external node and the second node is performed, so that the grounding target and the grounding mode can be easily selected, and the flow of noise into the electric device can be reduced.

[0014] The grounding characteristic converter may further include a third node connected to an external field ground that is not substantially connected to the first grounding terminal. The switch may connect the external node to one of the first to third nodes in accordance with an operation of an operator. Thus, even when the potential of the first ground terminal is likely to fluctuate, the potential of the first ground terminal is stabilized.

The load may include a second ground terminal. In this case, the ground characteristic conversion device may include a fourth node connected to the second ground terminal, and one end connected to the first ground terminal. A second resistor connected to a ground end, a fifth node connected to the other end of the second resistor, and the fourth node according to an operation of an operator. And a second switch connected to one of the third node and the fifth node. According to such a grounding characteristic conversion device, when the potential at the ground end of the load is fixed to the arithmetic mean of the potentials of the respective transmission paths, the connection between the fourth node and the first node is established, and the potential is substantially in phase with the load. When the applied noise is consumed, the fourth node is connected to the fifth node, and the potential of the ground terminal of the load is changed to the field ground in order to prevent the fluctuation of the potential of the ground terminal of the power source from affecting the load. When the potential is fixed to the potential of the fourth node and the third node, the operation of connecting the fourth node to the third node and the like are performed, so that the grounding target and the mode of the grounding can be easily selected, and the inflow of noise into the electric equipment is reduced. It is reduced.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a grounding characteristic converter according to an embodiment of the present invention will be described with reference to a grounding switch for reducing the flow of noise into a load driven by AC power.

FIG. 1 shows a physical configuration of a grounding switch according to an embodiment of the present invention. As shown in the figure, this grounding switch includes capacitors C1 and C2 and a switch SW.
1 and SW2, and resistors R1 and R2.

The capacitors C1 and C2 have substantially equal capacitance and are cascaded to form a series circuit. Both ends of the series circuit formed by the capacitors C1 and C2 are connected one-to-one to a pair of poles provided at an output end of an external AC power supply ACV that supplies single-phase AC power. Note that the AC power supply ACV generates a single-phase AC voltage between both poles of its own output terminal.

Further, both poles of the output terminal of the AC power supply ACV are:
It is connected one-to-one to a power input terminal of an external load Z having a power input terminal composed of a pair of poles. The load Z includes an electric device to which single-phase AC power is supplied.
The AC voltage applied between both poles of the power input terminal of the load Z is
For example, in order to drive an electric device constituting the load Z, the voltage is applied to the electric device. The load Z has a ground end, and the ground end of the load Z is connected to, for example, a housing made of a conductor of an electric device constituting the load Z.

The switch SW1 is composed of a rotary switch having three contacts in one circuit, and has terminals acom and a1 to a3. The switch SW1 is operated between the terminal acom and the terminal a1, the terminal acom and the terminal a2, and the terminal acom and the terminal a2 in accordance with the operation of the operator.
3 and one of them is made conductive.

The terminal acom of the switch SW1 is connected to a connection point between the capacitors C1 and C2. Terminal a1
Are connected to a ground terminal of the AC power supply ACV.
The terminal a2 is connected to the ground terminal of the AC power supply ACV via the resistor R1. The terminal a3 is connected to a field ground FG including a ground electrode buried in the ground. The ground end of the AC power supply ACV is connected to, for example, a conductor housing of a device constituting the AC power supply ACV.

The switch SW2 has substantially the same configuration as the switch SW1, and has terminals bcom and b1 to b
3 is provided. The switch SW2 is connected to the terminal bco between the terminal bcom and the terminal b1 according to the operation of the operator.
Any one of between m and the terminal b2 and between the terminal bcom and the terminal b3 is conducted.

The terminal bcom of the switch SW2 is connected to the load Z
Connected to the ground end of the Terminal b1 is an AC power supply
V is connected to the ground terminal provided. The terminal b2 is connected to the ground terminal of the AC power supply ACV via the resistor R2. The terminal b3 is connected to the field ground FG.

The resistor R1 is connected to the switch SW as described above.
1 terminal a2 and the ground terminal of the AC power supply ACV. The resistor R2 is connected to the switch SW2 as described above.
Of the AC power supply ACV.

A state in which the terminals acom-a1 of the switch SW1 are connected to each other (hereinafter, referred to as a "first state").
Thus, an AC voltage is generated between the two electrodes at the output end of the AC power supply ACV. In this case, the AC voltage is applied across the load Z.

On the other hand, the potential at the connection point between the capacitors C1 and C2 is substantially equal to the arithmetic average of the potentials at the respective poles at the output terminal of the AC power supply ACV. Therefore, the potential of the ground terminal of the AC power supply ACV, which is connected to the connection point of the capacitors C1 and C2, is also substantially equal to the arithmetic average of the potential of each pole of the output terminal of the AC power supply ACV.

As a result, in the first state, the AC power supply AC
Noise (normal mode noise) applied to both poles of the output terminal of V so that the potentials of both poles fluctuate at substantially the same amplitude and in opposite phases is substantially equal to the potential of the ground terminal of the AC power supply ACV. Do not fluctuate.

In the first state, noise (common mode noise) is applied to both poles of the output terminal of the AC power supply ACV so that the potentials of both poles fluctuate substantially in equal amplitude and in phase. AC power supply on the other hand
If the potential of the ground terminal of the capacitor is not affected by the variation of the potential caused by the common mode noise, the capacitors C1 and C2
A current flows between the connection point (1) and the ground terminal of the AC power supply ACV. As a result, substantially no noise current due to the common mode noise flows through the load Z.

Then, in the first state, the switch S
If the terminals bcom-b1 of W2 are connected to each other, the potential of the ground terminal of the load Z becomes substantially equal to the potential of the ground terminal of the AC power supply ACV. Therefore, noise current caused by the common mode noise generated by the load Z itself also flows to the ground terminal of the AC power supply ACV.

When the AC power supply ACV itself generates common mode noise, the common mode noise is usually
It is applied to both poles of the output terminal of the AC power supply ACV. Therefore,
In the first state, the common mode noise generated by the AC power supply ACV is substantially removed from the power supplied to the load Z.

In the first state, the switch SW
When the two terminals bcom-b2 are connected to each other, and when common mode noise is applied to both poles of the power input terminal of the load Z, a noise current caused by the common mode noise flows through the resistor R2. Then, as a result of the noise current flowing through the resistor R2, the common mode noise applied to the power input terminal of the load Z is converted into heat energy by power loss between both ends of the resistor R2 and consumed. Except when the common mode noise applied to the load Z substantially functions as a constant current source, the noise current flowing through the resistor R2 decreases as the resistance value of the resistor R2 increases. Therefore, as the resistance value of the resistance value R2 increases,
The noise current flowing through the load Z due to the common mode noise is effectively removed.

On the other hand, the potential of the ground terminal of the load Z is equal to the potential of the ground terminal of the AC power supply ACV minus the voltage corresponding to the voltage drop generated across the resistor R2 (the resistance is equal to the resistance of the resistor R2). The direction of the current flowing through the switch R2 is a positive direction from the terminal b2 of the switch SW2 to the ground terminal of the AC power supply ACV.) However, AC power supply ACV
Is substantially equal to the potential of the connection point between the capacitors C1 and C2, the resistor R2 receives a current caused by the normal mode noise applied between the two electrodes at the output terminal of the AC power supply ACV. Practically does not flow.

Therefore, in the first state, the switch S
When the terminals bcom and b2 of W2 are connected to each other, the common mode noise applied to both poles of the power input end of the load Z is substantially removed.

In the first state, the switch SW
If the two terminals bcom-b3 are connected to each other,
The potential of the ground terminal of the load Z becomes substantially equal to the potential of the field ground FG. Therefore, even if the potential of the ground terminal of the AC power supply ACV fluctuates, the potential of the ground terminal of the load Z does not substantially fluctuate. Therefore, in the first state, and
When the terminals bcom and b3 of the switch SW2 are connected to each other, the noise current flowing to the ground terminal of the AC power supply ACV is prevented from flowing to the ground terminal of the load Z.

Next, the terminal acom-a of the switch SW1
It is assumed that an AC voltage is generated between both poles of the output terminal of the AC power supply ACV in a state where the two are connected to each other (hereinafter, referred to as a “second state”). In the second state, the AC power source A
The AC voltage generated between the two terminals of the output terminal of the CV is applied across the load Z, and the potential at the connection point of the capacitors C1 and C2 is substantially the arithmetic average of the potential of each of the output terminals of the AC power supply ACV. Is equal to

The potential at the ground terminal of the AC power supply ACV is obtained by subtracting a voltage corresponding to a voltage drop generated between both ends of the resistor R1 from an arithmetic average of potentials at respective poles of the output terminal of the AC power supply ACV. (Note that the resistor R1
The direction of the current flowing through the switch SW1 from the terminal a2 of the switch SW1 to the ground terminal of the AC power supply ACV is a positive direction). As a result, even in the second state, the normal mode noise applied to both poles of the output terminal of the AC power supply ACV does not substantially change the potential of the ground terminal of the AC power supply ACV.

In the second state, when common mode noise is generated at both ends of the output terminal of the AC power supply ACV, a noise current caused by the common mode noise is generated by the resistor R.
Flow to 1. Therefore, if the resistance value of the resistor R1 is sufficiently lower than the output impedance of the external noise source that generates the common mode noise that causes the noise current to flow through the resistor R1, the noise generated by the noise source The magnitude of the voltage applied to the load Z is negligible compared to the magnitude of the entire noise voltage, including the magnitude canceled by the voltage drop inside the noise source. Then, as a result of the noise current flowing through the resistor R1, the common mode noise is converted into thermal energy by power loss between both ends of the resistor R1 and consumed.

Then, in the second state, the switch S
If the terminals bcom-b1 of W2 are connected to each other, the potential of the ground terminal of the load Z becomes substantially equal to the potential of the ground terminal of the AC power supply ACV. Therefore, the normal mode noise applied to both poles of the output terminal of the AC power supply ACV does not substantially change the potential of the ground terminal of the load Z.

However, in the second state, and when the switch S
In a state where the terminals bcom and b1 of W2 are connected to each other, a part of the common mode noise applied to both poles of the output terminal of the AC power supply ACV passes through the AC power supply AC via the load Z.
V flows to the ground end. Therefore, this ground switch is set in the second state and at the terminal bcom-b of the switch SW2.
1 are connected to each other so that the load Z
In order to prevent the application of common mode noise to the common mode noise, it is desirable that the input impedance of the load Z to the common mode noise be sufficiently high.

In the second state, the switch SW
If the terminals bcom and b2 are connected to each other, and if a noise voltage caused by the common mode generated by the load Z itself is generated between both poles of the power input terminal of the load Z,
The noise current caused by this common mode noise is the resistance R
Flow to 2. As a result, this common mode noise is consumed by the resistor R2.

On the other hand, the potential of the ground terminal of the load Z is equal to the potential of the ground terminal of the AC power supply ACV minus the voltage corresponding to the voltage drop across the resistor R2, and is equal to the potential of the ground terminal of the AC power supply ACV. Is substantially equal to the potential at the junction of capacitors C1 and C2 plus a voltage corresponding to the voltage drop across resistor R1. Therefore, the resistor R
A current caused by normal mode noise applied between both electrodes of the output terminal of the AC power supply ACV substantially does not flow through 1 and R2.

Accordingly, in the second state, the switch S
In a state where the terminals bcom and b2 of W2 are connected to each other, the common mode noise applied to both poles of the output terminal of the AC power supply ACV and the common mode noise generated by the load Z itself are reduced.

In the second state, the switch SW
If the two terminals bcom-b3 are connected to each other,
The potential of the ground terminal of the load Z is substantially equal to the potential of the field ground FG. Even if the potential of the ground terminal of the AC power supply ACV fluctuates, the potential of the ground terminal of the load Z does not substantially fluctuate. Therefore, in the second state and when the terminals bcom and b3 of the switch SW2 are connected to each other, the noise applied to the ground terminal of the AC power supply ACV is not substantially supplied to the load Z.

Next, the terminal acom-a of the switch SW1
It is assumed that an AC voltage is generated between both poles of the output terminal of the AC power supply ACV in a state where the three are connected to each other (hereinafter, referred to as a “third state”).

Also in this case, the potential at the connection point between the capacitors C1 and C2 is substantially equal to the arithmetic average of the potential at each pole at the output terminal of the AC power supply ACV. In addition, the capacitor C
The potential at the connection point of 1 and C2 is also substantially equal to the potential of the field ground FG connected to the connection point of the capacitors C1 and C2 via SW1. And
In the third state, normal mode noise applied to both poles of the output terminal of the AC power supply ACV does not substantially change the potential of the ground terminal of the AC power supply ACV. Therefore, noise current caused by common mode noise applied to both poles of the output terminal of the AC power supply ACV flows between the connection point between the capacitors C1 and C2 and the field ground FG.

Then, in the third state, the switch S
If the terminals bcom-b1 of W2 are connected to each other, the potential of the ground terminal of the load Z becomes substantially equal to the potential of the ground terminal of the AC power supply ACV. Therefore, the noise current caused by the common mode noise generated by the load Z itself is
Of the AC power supply ACV. As a result, in the third state, the terminal b of the switch SW2
com-b1 are connected to each other,
The potential of the ground terminal of the AC power supply ACV is prevented from fluctuating due to the common mode noise applied between both electrodes of the output terminal of the CV, and the noise current is prevented from flowing through the ground terminal of the AC power supply ACV. However, it is desirable that the amount by which the potential of the ground terminal of the AC power supply ACV fluctuates due to the noise current flowing to the ground terminal of the AC power supply ACV due to the common mode noise generated by the load Z itself be as small as possible.

In the third state, the switch SW
If the two terminals bcom-b2 are connected to each other,
When common mode noise is applied to both poles of the power input terminal of the load Z, or when the load Z itself generates common mode noise, noise current caused by these common mode noises flows through the resistor R2. . Then, this noise current flows through the resistor R2. This common mode noise is consumed by the resistor R2.

On the other hand, the potential of the ground terminal of the load Z is equal to the potential of the ground terminal of the AC power supply ACV minus a voltage corresponding to the voltage drop generated across the resistor R2. , The current caused by the normal mode noise applied between the two electrodes at the output terminal of the AC power supply ACV does not substantially flow.

Therefore, in the third state, the switch S
When the terminals bcom and b2 of W2 are connected to each other, the noise current flowing through the load Z due to the common mode noise applied to both poles of the power input end of the load Z is reduced.

In the third state, the switch SW
If the two terminals bcom-b3 are connected to each other,
Both the potential of the ground terminal of the AC power supply ACV and the potential of the ground terminal of the load Z are substantially equal to the potential of the field ground FG. For this reason, regardless of the potential of the ground terminal of the AC power supply ACV, the smaller the ground resistance of the field ground FG, the smaller the fluctuation of the potential. On the other hand, the larger the ground resistance, the smaller the noise current flowing to the load Z.

The configuration of the ground switch is not limited to the above. For example, the ground switch may include a plurality of resistors, not limited to the resistor R1, to be connected between the connection point of the capacitors C1 and C2 and the ground terminal of the AC power supply ACV. In this case, the switch SW1 is
According to the operation of the operator, one of the plurality of resistors may be connected between the connection point of the capacitors C1 and C2 and the ground terminal of the AC power supply ACV.

The ground switch may include a plurality of resistors for connection between the ground terminal of the load Z and the ground terminal of the AC power supply ACV, not limited to the resistor R2. In this case, the switch SW2 may connect one of the plurality of resistors between the ground terminal of the load Z and the ground terminal of the AC power supply ACV according to the operation of the operator.

The resistors R1 and R2 need not be elements having only a pure resistance component, but may have a reactance component. Therefore, this grounding switch is connected to a resistor R1 or R2 (otherwise, a resistor connected between the connection point of the capacitors C1 and C2 and the grounding terminal of the AC power supply ACV, Instead of a resistor connected between the power supply ACV and the ground terminal), a filter having an arbitrary frequency characteristic may be provided.

[0054]

As described above, according to the present invention, the grounding characteristics for enabling easy selection of the grounding target and the grounding mode so as to reduce the flow of noise into the electric equipment. A conversion device is realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a grounding switch according to an embodiment of the present invention.

[Explanation of symbols]

 ACV AC power supply C1, C2 Capacitor FG Field ground R1, R2 Resistor SW1, SW2 Switch Z Load

Claims (7)

[Claims] An electric potential corresponding to an arithmetic average of electric potentials of a pair of transmission paths for transmitting single-phase AC power supplied from an external power source having a first ground terminal to an external load is calculated. An average potential generating means for generating a voltage at a first node included in a first node; a second node connected to the first ground terminal; a first resistor having one end connected to the first ground terminal; A third node connected to the other end of the first resistor; and a second node connected to the second node according to an operation of an operator.
And a first switch connected to one of the third nodes. 2. The apparatus according to claim 1, further comprising: a fourth node connected to an external field ground that is not substantially connected to the first ground terminal, wherein the first switch is connected to the second switch according to an operation of an operator. The ground characteristic converter according to claim 1, wherein one node is connected to one of the second to fourth nodes. 3. The load has a second ground terminal, a fifth node connected to the second ground terminal, and a second resistor having one end connected to the first ground terminal. A sixth node connected to the other end of the second resistor; and a fifth node connected to one of the second, fourth, and sixth nodes according to an operation of an operator. The second to connect
The ground characteristic conversion device according to claim 2, further comprising: a switch. 4. The average potential generating means includes: a first capacitor having one end connected to one of the pair of transmission lines and the other end connected to the first node; And a second capacitor having the other end connected to the first node and having a capacitance substantially equal to the first capacitor. 4. The grounding characteristic converter according to item 2 or 3. 5. A first node connected to a first ground terminal provided in an external power source; a first resistor having one end connected to the first ground terminal; and the first resistor. A second node connected to the other end of the vessel, and a potential of each of a pair of transmission paths for transmitting single-phase AC power supplied from the external power source to an external load in accordance with an operation of an operator. A first switch that connects an external node that generates a potential equivalent to an arithmetic average to one of the first and second nodes. 6. The semiconductor device according to claim 1, further comprising a third node connected to an external field ground not substantially connected to the first ground terminal, wherein the first switch is connected to the external field according to an operation of an operator. The ground characteristic conversion device according to claim 5, wherein the first node is connected to one of the first to third nodes. 7. The load has a second ground terminal, a fourth node connected to the second ground terminal, and a second resistor having one end connected to the first ground terminal. A fifth node connected to the other end of the second resistor; and a fourth node connected to one of the first, third, and fifth nodes according to an operation of an operator. The second to connect
The ground characteristic conversion device according to claim 6, further comprising: a switch.