JP3389001B2 - Ground detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground detection device for detecting a disconnection of a ground wire of a load device and notifying a detection result.

[0002]

2. Description of the Related Art For example, as a grounding detecting device for detecting a disconnection of a grounding wire of a load device such as a motor with a fail-safe structure, there is one proposed by the present applicant in Japanese Patent Application No. 7-182781. The ground detection principle of such a ground detection device will be described with reference to FIG.

That is, two ground wires 4 and 5 are provided in a motor case 3 which houses a motor coil 2 of a motor 1 as a load device, and one ground wire 5 is provided with a secondary winding N ₁₂ of a transformer T1. Connect in series. Then, an AC signal is applied from the signal generator 6 to the primary winding N ₁₁ of the transformer T1. When both the ground lines 4 and 5 are normal, the impedance of the primary winding N ₁₁ of the transformer T1 is small, and the terminal voltage of the resistor R connected in series with the primary winding N ₁₁ becomes high level. on the other hand,
When any of the ground lines 4 and 5 is broken, the impedance of the primary winding N ₁₁ of the transformer T1 increases and the terminal voltage of the resistor R decreases.

Therefore, for example, by supplying the terminal voltage output of the resistor R to the light emitting diode, turning on the light emitting diode at the high level output when the ground line is normal, and turning off the light emitting diode at the low level output, grounding is performed. It is possible to detect and notify the presence / absence of disconnection of the lines 4 and 5. By the way, when using the ground detection principle to detect ground,
In reality, the impedance of the primary winding N ₁₁ of the transformer T1 does not become infinite even when the ground is disconnected, and a current flows through the resistor R to generate a terminal voltage, which requires a device for turning off the light emitting diode. Become.

FIG. 9 shows an example of a concrete ground detection device. The same parts as those in FIG. 8 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 9, a commercial AC power supply for supplying the motor coil 2 of the motor 1 is used as the AC signal supplied to the primary winding N ₁₁ of the transformer T1 in which the secondary winding N ₁₂ is connected in series to the ground line 5. . In addition, the primary winding N ₁₁ of the transformer T1
The primary winding N ₂₁ of the transformer T2 for extracting the detection output is inserted in series to the power feeding line of the above. Secondary winding N of transformer T2
_A rectifying diode D, a zener diode ZD, and a light emitting diode PD are connected in series to ₂₂ .

According to this structure, when the ground lines 4 and 5 are normal, the output of the secondary winding N ₂₂ of the transformer T2 becomes equal to or higher than the threshold voltage of the Zener diode ZD, and the light emitting diode PD lights up to notify the normal ground. . On the other hand, when one of the ground lines 4 and 5 is broken, the output of the secondary winding N ₂₂ of the transformer T2 becomes lower than the threshold voltage of the Zener diode ZD, and the light emitting diode PD is turned off to notify the ground line break.

[0007]

However, in the method using the Zener diode ZD as shown in FIG.
When a short-circuit failure occurs in the Zener diode ZD, the light emitting diode PD may not be turned off even when the ground wire is disconnected, and there is a possibility that the normal grounding may be notified despite the disconnection of the ground wire. Have a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly reliable ground detection device which can reliably notify a ground wire disconnection without using a Zener diode. Another object of the present invention is to provide a ground detection device that also has a function of informing that the detection sensitivity of ground line abnormality has decreased.

[0009]

Therefore, according to the first aspect of the present invention, there is provided a grounding detection device for detecting the presence or absence of disconnection of the grounding wire of a load device, wherein the primary winding to which an AC signal is applied and the load. A first transformer having a secondary winding connected in series to one of two grounding wires connected to the case of the device, a primary winding connected in series with the primary winding of the first transformer, and the primary winding A second transformer having a secondary winding for extracting a change in the input signal of the line, and a sensor means for generating a sensor output according to the output of the secondary winding of the second transformer; and a sensor output of the sensor means. A notification means for notifying the presence or absence of a break in the grounding wire by directly applying commercial power to the primary winding of the first transformer, while the sensor means is connected to the secondary winding of the second transformer. Generates a constant voltage lower than the output voltage based on the output. Constant voltage generating means and a constant voltage output of the constant voltage generating means as a driving power source, and the rectified output of the secondary winding of the second transformer is directly input and level-verified to generate an output when a predetermined threshold value is exceeded. The level detecting means is provided, and the notifying means notifies that the ground line is normal when an output is generated from the level detecting means.

According to this structure, the constant voltage generating means generates a constant voltage based on the output from the secondary winding of the second transformer, and the level detecting means is driven by using this constant voltage as a driving power source. The second voltage before inputting to the constant voltage generating means
The output of the secondary winding of the transformer is directly input to the level detecting means as an input signal. If this input signal is greater than or equal to the predetermined threshold value set by the level verification means, the notification means operates with the output from the level verification means to notify that the ground line is normal. On the other hand, when the secondary winding output of the second transformer is lower than the threshold value, no output is generated from the level verification means and the notification means does not operate to notify the ground abnormality.

Further, it is not necessary to separately provide a drive power source for the level verification means, and further, if the secondary winding output of the second transformer becomes lower than the constant voltage generated by the constant voltage generation means, the level verification means can be driven. No output from the level verification means. Further, in the invention according to claim 2, when the sensor means and the notification means are housed in a metal case, one of the two ground wires connected to the load device is connected via the metal case. Grounded.

According to this structure, it is possible to simultaneously detect whether or not the grounding of the storage case of the sensor means and the notification means is normal. According to a third aspect of the invention, in the ground detection device for detecting the presence or absence of a break in the ground wire of the load device, one of the primary winding to which an AC signal is applied and one of the two ground wires connected to the case of the load device. Transformer having a secondary winding connected in series to the first winding and a tertiary winding for transmitting a change in the input signal of the primary winding, and a primary connected in series with the tertiary winding of the first transformer A winding, a secondary winding connected in series to the secondary winding of the first transformer on the one ground line, and a tertiary winding for extracting the differential output of the primary winding and the secondary winding of the secondary winding. A second transformer having a wire, an electric signal extracted by the third winding of the second transformer, and electricity transmitted to a series circuit of the third winding of the first transformer and the primary winding of the second transformer Consists of an alarm means for notifying the presence / absence of disconnection of the ground wire and a decrease in abnormality detection sensitivity based on the signal It was.

In such a configuration, the electrical signal extracted by the tertiary winding of the second transformer changes depending on whether the ground wire is normal or disconnected. The disconnection of the ground wire can be detected based on this change. In addition, the third winding of the first transformer and the first winding of the second transformer
When a disconnection occurs in the series circuit of the next winding, the differential function of the second transformer is lost, and the detection sensitivity of the increase in the ground resistance of the ground wire is reduced. This decrease in detection sensitivity can be known by the change in the electric signal of the series circuit.

According to a fourth aspect of the present invention, the notifying means includes a first light emitting diode and a second transformer which are inserted in a series circuit of the tertiary winding of the first transformer and the primary winding of the second transformer. And a second light emitting diode connected in series to the third winding of the above. In such a configuration, it is possible to know the disconnection or abnormality of the ground line by turning on / off each of the first and second light emitting diodes.

According to a fifth aspect of the invention, the notifying means includes a light projecting element inserted in a series circuit of the tertiary winding of the first transformer and the primary winding of the second transformer, and the light projecting element. Photocoupler composed of a light receiving element for receiving the optical signal, a first rectifier circuit for rectifying the AC output of the first photocoupler, and a light projecting device connected in series to the tertiary winding of the second transformer. Element and a light receiving element for receiving an optical signal from the light projecting element
A second photocoupler including a child, a second rectifier circuit that rectifies the AC output of the second photocoupler, and a logical product circuit that performs a logical product operation of the rectified outputs of the first and second rectifier circuits. A third light which is turned on by the output of the logical value 1 of the AND circuit
And a light emitting diode.

In such a configuration, when an abnormality occurs in each photocoupler or the like, the output from each corresponding rectifier circuit is stopped and the light emitting diode is turned off. Therefore, the configuration is fail-safe. According to a sixth aspect of the present invention, the notifying means is the secondary winding of the first transformer and the second winding of the second transformer.
A third photocoupler including a light projecting element that is inserted in the one ground line in series with the next winding and a light receiving element that receives an optical signal from the light projecting element, and an AC output of the third photocoupler. A third rectifying circuit for rectifying, a light projecting element inserted in a series circuit of the tertiary winding of the first transformer and a primary winding of the second transformer, and a light receiving element for receiving an optical signal from the light projecting element. And a fourth photocoupler that rectifies the AC output of the fourth photocoupler and superimposes the rectified output of the third rectifier circuit on the rectified output, and outputs the third transformer. A fifth rectifier circuit for rectifying the AC output extracted by the next winding, and a logical product circuit for generating an output when each output level of the fourth and fifth rectifier circuits is higher than each preset threshold level. , the fourth light emitting die lit by the output of the logical product circuit Constituted by a chromatography mode.

In such a configuration, the abnormality detection sensitivity can be set with high accuracy because the abnormality detection sensitivity can be set by the threshold value of the AND circuit that tests the extraction level of the tertiary winding of the second transformer. .

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of a first embodiment of a ground detection device according to the present invention. The same parts as those in the conventional example shown in FIG. 9 are designated by the same reference numerals. In FIG.
For example, in a motor 1 as a load device, a motor coil 2 is built in a metal motor case 3. Motor coil 2
Is connected to a commercial AC power supply (not shown) via a pair of power supply lines 7A and 7B. Two ground wires 4 and 5 are connected to the motor case 3, and the motor case 3 and the ground wires 4 and 5 are connected to each other.
5 and the earth closed circuit.

The first transformer T1 is connected to the AC power source.
Primary winding on the power supply lines 7A and 7B in parallel with the data coil 2
N₁₁Are connected in series and the secondary winding N is connected to the ground wire 5.₁₂Are in series
Connecting. Primary winding N of second transformer T2_{twenty one}Is the above
Primary winding N of 1 transformer T1 ₁₁And the feeder lines 7A and 7B
It is inserted in series between and. The above configuration is shown in FIG.
It has the same configuration as the one.

The output terminal of the secondary winding N ₂₂ for extracting the input signal change of the primary winding N ₂₁ of the second transformer T2 is connected to the rectifier circuit 11. The rectified output of the rectifier circuit 11 is input to a constant voltage regulator 12 as a constant voltage generating means which is smoothed by a smoothing capacitor C and is composed of a transistor and a resistor. The constant voltage output of the constant voltage regulator 12 is used as a power supply for driving and a window comparator as a level verification means.
Supplied to 13. The window comparator 13 uses the constant voltage output V _CC from the constant voltage regulator 12 as a power source and level-checks the smoothed output V from the smoothing capacitor C directly input to the input terminal. AC output is generated when the smoothed output level is within a predetermined threshold range set in advance, and no output is generated when the smoothed output level is outside the threshold range. In the present embodiment, the window upper limit of the threshold value of the comparator 13 it shall properly sets only the lower limit of the threshold V _TH as sufficiently large (V _CC <V _TH) as compared to the smoothed output. AC output window fin dough comparator 13 is supplied to the light-emitting diode PD of the notification means is rectified by a voltage doubler rectifier circuit 14. A constant voltage regulator is provided on the cathode side of the light emitting diode PD.
The constant voltage output V _CC from 12 is applied.

Here, the first and second transformers T1,
T2, the rectifier circuit 11, the constant voltage regulator 12, the window comparator 13, and the voltage doubler rectifier circuit 14 constitute a sensor means, and a commercial AC power source is used as a drive power source for the sensor means. The window comparator 13 has a power supply voltage V
It is a fail-safe configuration that generates an AC signal only when an input signal with a level within a predetermined threshold range higher than _CC is input and does not generate an AC signal at the time of failure, and such a fail-safe window comparator is US patent as a fail-safe window comparator / AND gate composed of multiple resistors and transistors
It is conventionally known in the specification of 4,661,880 and WO94 / 23303.

The voltage doubler rectifier circuit 14 is composed of two capacitors and two diodes to generate an output in which the voltage V _CC is superimposed on the rectified output based on the input signal. US Pat. No. 5,027,114 Book and international publication
It is conventionally known in WO94 / 23303 and the like. Next, the operation will be described.

When the ground wires 4 and 5 are normal, the primary winding N ₁₁ of the first transformer T1 is in a short-circuited state, so that the first transformer
The primary winding N ₁₁ of the impedance T1 is in a low impedance state.
Therefore, the potential between the feeder lines 7A and 7B is almost the same as that of the second transformer.
It is applied across the primary winding N _{21 of} T2 . Therefore, the high level output from the secondary winding N ₂₂ is input to the rectifier circuit 11. The window comparator 13 is driven by the constant voltage output V _CC input from the smoothing capacitor C to the window comparator 13 via the constant voltage regulator 12 based on the rectified output of the rectifier circuit 11. Then, the smoothing output V directly input from the smoothing capacitor C to the window comparator 13
Is higher than the threshold value V _{TH of} the window comparator 13, and an AC output is generated from the window comparator 13. The AC output of the window comparator 13 is the voltage doubler rectifier circuit 14
And is applied to the cathode side of the light emitting diode PD at a voltage higher than V _CC . Therefore, the light emitting diode PD
Lights up and indicates that the ground lines 4 and 5 are normal.

On the other hand, when either or both of the ground lines 4 and 5 are disconnected, the impedance of the primary winding N ₁₁ of the first transformer T1 increases and the primary winding N ₂₁ of the second transformer T2 increases. The input voltage becomes low, and the output from the secondary winding N ₂₂ becomes low level. Therefore, the window comparator 13
The smoothing output V that is input to is also decreased, and when the smoothing output V becomes lower than the threshold value V _TH , the AC output of the window comparator 13 is stopped. As a result, the light emitting diode PD is turned off and the disconnection of the ground lines 4 and 5 is notified.

Further, the decrease in the output level of the secondary winding N ₂₂ of the second transformer T2 due to the disconnection of the ground lines 4 and 5 is large,
If the constant voltage V _CC from the constant voltage regulator 12 becomes lower than the drive voltage level of the window comparator 13, the operation of the window comparator 13 is stopped and the output is stopped, so that the light emitting diode PD is also turned off and the disconnection is notified. .

Further, although the ground lines 4 and 5 are not broken, the second transformer T can be used even when the ground resistance becomes large.
The output level on the secondary winding N ₂₂ side of No. 2 decreases (the degree of decrease is smaller than that at the time of disconnection). Therefore, by appropriately setting the threshold value V _TH of the window comparator 13, it is possible to turn off the light emitting diode PD even when the ground resistance exceeds a predetermined value. Therefore, the circuit of this embodiment has an advantage that not only the disconnection of the ground lines 4 and 5 but also the abnormality of the ground resistance can be detected and notified.

Further, since the commercial AC power supply supplied to the motor coil 2 is directly used as the drive power supply for the sensor means, the wiring system can be simplified as compared with the case where a separate drive power supply for the sensor means is provided. . Further, when the signal generator 6 shown in FIG. 8 is used as the driving power source for the sensor means, it is normally configured to generate a high frequency signal from a commercial power source using a transformer and a rectifier circuit. By directly using the commercial power supply, these circuits become unnecessary and the circuit configuration can be simplified.

Even when the window comparator 13 or the voltage doubler rectifier circuit 14 fails, the output of each circuit is stopped and the light emitting diode PD is turned off. Therefore, fail-safe property at the time of circuit failure can be ensured and reliability is improved. high. Next, a second embodiment of the present invention will be described. FIG. 2 shows a circuit diagram of the second embodiment. The same parts as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, the drive power supply for the window comparator 13 and the input signal are generated in different systems. 2, a second transformer T2 to the tertiary winding N ₂₃ is provided, provided the 3 rectifier circuit 11 for rectifying an output of the winding N ₂₃ 'and the rectifier circuit 11' smoothing capacitor C the rectified output to smoothing ' , The smoothed output of the smoothing capacitor C ′ is used as the input signal of the window comparator 13.
On the other hand, the output of the secondary winding N ₂₂ of the second transformer T2 is as shown in FIG.
Similarly, it is supplied as a driving power source for the window comparator 13 via the rectifying circuit 11, the smoothing capacitor C and the constant voltage regulator 12.

Even if the circuit is constructed as in the second embodiment, the same effect as that of the first embodiment can be obtained. However,
Since the rectifier circuit 11 'and the smoothing capacitor C'are increased, the configuration of the first embodiment can be made cheaper than the configuration of the second embodiment. Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the third embodiment, when the sensor means and the notification means are housed in a metal storage case, the grounded state of the storage case can be detected at the same time.
In FIG. 3, a metal housing case 20 houses a first transformer T1, a second transformer T2, a disconnection detection circuit unit 21, and a light emitting diode PD. Where disconnection detection circuit
In the circuit of FIG. 1, 21 is a rectifying circuit 11, a smoothing capacitor C,
The circuit of FIG. 2 includes a constant voltage regulator 12, a window comparator 13, a voltage doubler rectifier circuit 14, and the like.
11, 11 ', smoothing capacitors C, C', constant voltage regulator 12, window comparator 13, and voltage doubler rectifier circuit 14
Etc. shall be included.

One end of the primary winding N ₁₁ of the first transformer T1 is connected to the power supply line 7B via the terminal 22A, and one end of the primary winding N ₂₁ of the second transformer T2 is connected via the terminal 22B. Connect to the power supply line 7A. Further, one end of the secondary winding N ₁₂ of the first transformer T1 is connected to the ground wire 5 via the terminal 22C, and the other end is connected to the ground via the terminal 22D, the storage case 20 and the terminal 22E, The motor case 3 is grounded via the storage case 20.

According to this structure, if the grounding wires of the motor case 3 and the housing case 20 are normally connected, the light emitting diode PD is lit by the same operation as described above to notify that the grounding is normal. . On the other hand, if any one of the terminals 22C to 22E is disconnected, the light emitting diode PD is turned off, so that it is possible to detect and inform whether or not the housing case 20 is normally grounded simultaneously with the motor case 3. The terminal 22A, even light-emitting diode PD If 22B is out of course be off.

Since the ground detection operation based on the output of the secondary winding N ₂₂ of the second transformer T2 is the same as that in each of the above-mentioned embodiments, its explanation is omitted here. Next, a first embodiment of the ground detection device for detecting the disconnection of the ground wire using the principle of the differential transformer will be described with reference to FIG. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 4, there are three first transformers T1 '.
Winding N₁₁, N₁₂, N₁₃Have. Winding N₁₁With Figure 1
Similarly, connect the power supply lines 7A and 7B in series, and connect the winding N₁₂Figure 1
Connect to the ground wire 5 in series in the same manner as₁₃Will be described later
Winding N of the second transformer T2 ' _{twenty one}And current path connected in series
l₁Make up. The second transformer T2 'also has three windings N
_{twenty one}, N_{twenty two}, N_{twenty three}Have. Winding N_{twenty one}Is the first as mentioned above
Winding N of transformer T1 '₁₃And current path l₁In series connection
And winding N _{twenty two}Is a second light emitting diode for notifying disconnection via a resistor.
Connected in series with the light emitting diode PD as an ion
Flow path l₂Forming a winding N_{twenty three}Of the first transformer T1 '
Winding N₁₂Is connected to the ground wire 5 in series.

In order to ensure that the ground resistance detection sensitivity does not decrease in the current path l _{1 in} which the winding N ₁₃ of the first transformer T1 'and the winding N ₂₁ of the second transformer T2' are connected in series. Light emitting diode P as the first light emitting diode of
D'and a resistor are inserted in series. In the present embodiment, the light emitting diodes PD and PD ′ form a notification means. Then, in the winding N _22, which is an output winding of the second transformer T2 ′, a differential output between the winding N ₂₁ and the winding N ₂₃ is generated,
Each winding N of the first transformer T1 'and the second transformer T2'
The winding directions of ₁₁ , N ₁₂ , N ₁₃ , N ₂₁ , N ₂₂ , and N ₂₃ are determined.

Next, the operation will be described. AC power supply line
Winding N of the first transformer T1 'via 7A and 7B₁₁Exchange
Current voltage V_inThe current flowing through the ground wire 5 when
i_EAnd current path l₁The current flowing through_rAnd then the current
Route l₂The current flowing through₀And Ground lines 4 and 5 are positive
In normal cases, ground wire 5, current path l₁, L₂Each electric current flowing to
Flow i _E, I_r, I₀The relationship between the size and direction of
As shown. That is, section t in FIG.₁Well then
In the 2 transformer T2 ', the current i_EAnd i_rDifference of
Flow i₀Is the current path l₂In the forward direction of the light emitting diode PD
Flowing. At this time, the current path l₁Also current i_rIs a light emitting die
It flows in the forward direction of the ode PD '. Section t₂Then, section t
₁And current i_EFlows in the opposite direction, and the current i_rWhen
i₀Flow direction is the opposite direction of the light emitting diodes PD, PD '
It will be blocked and will not flow.

As described above, when the ground lines 4 and 5 are normal, the current i ₀ is generated in the current path l ₂ and the light emitting diode PD is turned on to report the normality of the ground lines 4 and 5. Also,
The current i _r flowing through the current path l ₁ also turns on the light emitting diode PD ′, which indicates that the disconnection detection sensitivity is good. On the other hand, if any one of the ground lines 4 and 5 is broken, the current i _E does not flow and only the current i _r shown by the broken line in FIG.
The flow direction of the current i ₀ is limited by the light emitting diode PD and does not flow, so that the light emitting diode PD does not light up and a disconnection can be reported.

As the ground resistance of the ground lines 4 and 5 increases, the current i _E decreases, the difference between the currents i _E and i _{r in} the section t ₁ decreases, and the current i ₀ decreases. When the ground resistance exceeds a certain value, the difference becomes substantially zero or less, and the light emitting diode PD is turned off. Therefore, an abnormality in the ground resistance can also be reported. In addition, the current path l
_{When 1} is disconnected, the light emitting diode PD 'is turned off. Since the current i _r does not flow, the current i ₀ has a value corresponding to the current i _E. In this case, since the second transformer T2 'does not have a differential function, the light emitting diode PD can be provided if the current i _E flows even if the ground resistance exceeds the normal range and becomes large.
Lights up and reports normality. Therefore, when the current path l ₁ is broken, the detection sensitivity of the ground resistance is lowered, and the light emitting diode PD ′ is turned off.
It is possible to report a decrease in ground resistance detection sensitivity.

Next, FIG. 6 shows a second embodiment of a structure in which one light emitting diode serves to notify the detection sensitivity decrease and the ground line abnormality by using a photo coupler. The same parts as those in the embodiment of FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 6, a first photocoupler composed of a light emitting diode PD1 and a phototransistor PT1 is provided on the current path l1 side.
31 is provided. On the side of the current path l2, the light emitting diode PD2
And a second photocoupler 32 including a phototransistor PT2 is provided. Each phototransistor PT1, PT
The respective collector outputs of 2 are rectified by the voltage doubler rectifier circuits 33 and 34 as the first and second rectifier circuits. Double voltage rectifier circuit 3
3, 34 superimpose the constant voltage Vcc on the rectified output and output it to the window comparator 13 shown in FIG. The output of the window comparator 13 turns on the light emitting diode PD corresponding to the third light emitting diode in the present embodiment.
The window comparator 13 corresponds to the above-mentioned U.S. Pat.
880 Specification and International Publication WO94 / 23303
As described above, it substantially has the function of an AND gate, performs a logical product operation of both voltage doubler rectifier circuits 33 and 34, and outputs the logical output to the voltage doubler rectifier circuit 14. Therefore, the window comparator 13 corresponds to a logical product circuit.

Next, the operation will be described. When the ground lines 4 and 5 are normal, the currents i _r and i ₀ flow as described with reference to FIG. 4, so that an AC signal is generated from the first and second photocouplers 31 and 32, and the double voltage rectification is performed. The rectified output from the circuits 33 and 34 causes the window comparator 13 to output a logical value of 1, and the light emitting diode PD is turned on through the voltage doubler rectifier circuit 14 to report that the ground lines 4 and 5 are normal.

On the other hand, when one of the ground lines 4 and 5 is disconnected,
When the ground resistance becomes large, the current i ₀ is limited by the light emitting diode PD2 and does not flow.
The output from 32 is stopped, the output level of the voltage doubler rectifier circuit 34 becomes smaller than the threshold value of the window comparator 13, the output from the window comparator 13 is stopped, and the light emitting diode PD is turned off. Also, the current path l ₁ is broken
When the detection sensitivity of the ground resistance decreases, the first photo coupler
Since the output from 31 is stopped, the output of the window comparator 13 is also stopped and the light emitting diode PD is turned off.

Then, the first and second photocouplers 31, 32
Alternatively, when the voltage doubler rectifier circuits 33, 34 fail, the input level of the window comparator 13 becomes smaller than the threshold value and the output of the window comparator 13 stops. Also, when the window comparator 13 fails, the output of the window comparator 13 becomes a logical value 0. Therefore, the ground detection circuit of the present embodiment has a fail-safe configuration because the light emitting diode PD is turned off to report an abnormality when the circuit fails.

Next, another embodiment will be described with reference to FIG. In FIG. 7, in the circuit of this embodiment, the current path l
The second photo coupler 32 provided on the ₂ side is removed, and the ground wire 5
On the side, the light emitting diode PD3 and the phototransistor PT
A third photo coupler 41 composed of 3 is provided. The output of the third photocoupler 41 is voltage-doubled and rectified by the voltage doubler rectifier circuit 42 corresponding to the third rectifier circuit, and the constant voltage V _CC is superposed and output to the voltage doubler rectifier circuit 33 'corresponding to the fourth rectifier circuit. The voltage doubler rectifier circuit 33 ′ superimposes the output of the voltage doubler rectifier circuit 42 on the rectified output of the first photocoupler 31 functioning as the fourth photocoupler in the present embodiment, and the window comparator 13 ′.
Output to. On the other hand, the current i ₀ flowing in the current path l ₂ is
It is directly rectified by the voltage doubler rectifier circuit 34 'corresponding to the fifth rectifier circuit and input to the window comparator 13'. According to the output of the window comparator 13 ', the light emitting diode P that functions as the fourth light emitting diode in this embodiment.
Turn on D.

The window comparator 13 'sets the threshold value on the input terminal side to which the rectified output of the voltage doubler rectifier circuit 33' is input.
Double voltage rectification circuits 33 ', 42 based on photocouplers 31, 41
When the rectified output was set to V ₀ of, V _CC + V ₀ and V _CC + 2V
Set between ₀ . Next, the operation will be described. Ground wire 4,
When 5 is normal, the AC output is generated from the first and third photocouplers 31 and 41, so that the output V ₀ + V _CC is generated from the voltage doubler rectifier circuit 42 and V is output from the voltage doubler rectifier circuit 33 '. ₀ by superimposing V _CC + V _0, the output of V _CC + 2V ₀ is generated. Further, since the rectified output higher than the threshold value of the window comparator 13 'is also generated from the voltage doubler rectifier circuit 34', both input levels of the window comparator 13 'become higher than the threshold value, and the logical value from the window comparator 13' is changed. The output of 1 is generated and the light emitting diode PD is turned on.

On the other hand, when disconnection occurs in the ground lines 4 and 5,
The output of the voltage doubler rectifier circuit 42 becomes V _CC ,
33 'output was superimposing V _CC to V _0, V _CC + V _0, and the window comparator 13' is smaller than the threshold. Therefore, no output is generated from the window comparator 13 'and the light emitting diode PD is turned off. When the current path l ₁ is broken, the output from the first photocoupler 31 is stopped, so the output from the voltage doubler rectifier circuit 33 'is
The output from the voltage doubler rectifier circuit 42 becomes V _CC + V ₀ , and the output of the window comparator 13 'stops.

In the circuit of this embodiment, assuming that the two input terminals of the window comparator 13 'are A and B, the output of the voltage doubler rectifier circuit 34' of the window comparator 13 'is input because the detection sensitivity of the ground resistance is lowered. It is determined by the threshold value on the input terminal B side. That is, the current i _E changes according to the magnitude of the ground resistance of the ground lines 4 and 5. The current i ₀ flowing through the current path l ₂ changes in proportion to this change, and the voltage doubler rectifier circuit 34 '
The output level of changes. Therefore, if the threshold value of the input terminal B of the window comparator 13 'is set high, the light emitting diode PD can be turned off even if the ground resistance is slightly increased, and the detection sensitivity can be increased. And
Since the threshold value can be set more accurately than in the case of FIG. 6, the accuracy of the ground resistance detection sensitivity can be increased.

[0048]

As described above, according to the first aspect of the present invention, the disconnection state of the ground line can be reliably notified without using the Zener diode. In addition, even if the ground wire is not broken, it is possible to notify even when the ground resistance is abnormal.

According to the second aspect of the present invention, the abnormality of the grounding wire of the storage case for storing the sensor means and the like can be notified at the same time. According to the inventions of claims 3 and 4, when the ground wire is broken or the ground resistance increases,
The second light emitting diode can be turned off and a notification can be given by a change in the extraction output of the tertiary winding of the second transformer. In addition, when the differential function is lost due to the disconnection of the series circuit of the tertiary winding of the first transformer and the primary winding of the second transformer, and the detection sensitivity of the increase in the ground resistance of the ground line decreases, , Can be notified by turning off the first light emitting diode.

According to the invention of claim 5, in addition to the effect of being able to report the disconnection of the ground wire, the increase of the ground resistance and the decrease of the detection sensitivity, the output of the AND circuit is stopped at the time of the circuit failure and the third light emitting diode is It can be turned off to notify the abnormality, and the configuration becomes fail-safe. According to the invention of claim 6, in addition to the effect of notifying the disconnection of the ground wire, the increase of the ground resistance and the decrease of the detection sensitivity, the abnormality detection sensitivity can be set by the threshold value of the AND circuit , and the abnormality detection sensitivity setting can be performed. Can be performed with high precision.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a ground detection device of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a ground detection device of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the ground detection device of the invention.

FIG. 4 is a circuit diagram showing an embodiment using a differential transformer function.

5 is a relational diagram of respective currents flowing in the circuit of FIG.

FIG. 6 is a diagram showing another embodiment using a differential transformer function.

FIG. 7 is a diagram showing still another embodiment using a differential transformer function.

FIG. 8 is an explanatory diagram of the detection principle of the ground detection device of the present invention.

FIG. 9 is a circuit diagram of a conventional ground detection device.

[Explanation of symbols]

1 motor 2 motor coils 3 motor case 4,5 ground wire 7A, 7B power supply line 12 Constant voltage regulator 13, 13 'window comparator 21 storage case 22A to 22E terminals T1, T1 '1st transformer T2, T2 '2nd transformer PD, PD 'light emitting diode 31, 32, 41 Photo coupler 33, 33 ', 34, 34', 42x voltage rectifier circuit

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02H 3/00 H02H 3/16 G01R 19/165 G01R 31/02

Claims (6)

(57) [Claims] 1. A ground detection device for detecting the presence or absence of a break in the ground wire of a load device, wherein one of two ground wires connected to the primary winding to which an AC signal is applied and the case of the load device. A first transformer having a secondary winding connected in series and the first transformer
A second transformer having a primary winding connected in series with the primary winding of the transformer and a secondary winding extracting the change in the input signal of the primary winding; A sensor unit for generating a corresponding sensor output, and a notifying unit for notifying the presence / absence of disconnection of the ground line based on the sensor output of the sensor unit, wherein a commercial power supply is provided to the primary winding of the first transformer. While being directly applied, the sensor means drives a constant voltage generating means for generating a constant voltage lower than the output voltage based on the output of the secondary winding of the second transformer, and a constant voltage output of the constant voltage generating means. The power supply is provided with a level verification means for directly inputting the rectified output of the secondary winding of the second transformer and performing a level verification to generate an output when a predetermined threshold value is exceeded, and an output is generated from the level verification means. Sometimes the notification means is grounded A ground detection device having a configuration for notifying a normal line. 2. When the sensor means and the notifying means are housed in a metal case, one of two ground wires connected to the load device is grounded via the metal case. The ground detection device according to claim 1. 3. A grounding detection device for detecting the presence or absence of a break in the grounding wire of a load device, wherein a primary winding to which an AC signal is applied and one of two grounding wires connected to the case of the load device are connected in series. A primary winding having a secondary winding and a tertiary winding to which the input signal change of the primary winding is transmitted, and a primary winding connected in series with the tertiary winding of the first transformer, A secondary winding connected in series with the secondary winding of the first transformer and a tertiary winding for extracting a differential output of its own primary winding and secondary winding are provided on the one ground line. Based on the electric signal extracted by the second transformer and the tertiary winding of the second transformer and the electric signal transmitted to the series circuit of the tertiary winding of the first transformer and the primary winding of the second transformer It is characterized in that it is provided with an informing means for informing the presence / absence of disconnection of the ground wire and a decrease in abnormality detection sensitivity. Ground detection apparatus according to. 4. The notifying means includes a first light-emitting diode inserted in a series circuit of a tertiary winding of the first transformer and a primary winding of a second transformer and a tertiary winding of the second transformer. The ground detection device according to claim 3, further comprising a second light emitting diode connected in series. 5. The light emitting device, which is inserted into a series circuit of a tertiary winding of the first transformer and a primary winding of the second transformer, and an optical signal from the light emitting element. A first photocoupler including a light receiving element, a first rectifying circuit for rectifying an AC output of the first photocoupler, a light projecting element connected in series to a tertiary winding of the second transformer, and the light projecting element. Photocoupler including a light receiving element that receives an optical signal from the second photocoupler, a second rectifier circuit that rectifies an AC output of the second photocoupler, and a logical product of rectified outputs of the first and second rectifier circuits An AND circuit that performs an operation and a logical value 1 of the AND circuit
The ground detection device according to claim 3, further comprising a third light emitting diode that is turned on by the output of the above. 6. The light emitting element, which is inserted into the one ground line in series with the secondary winding of the first transformer and the secondary winding of the second transformer, and the informing means. A third photocoupler including a light receiving element for receiving an optical signal, and the third photocoupler
A third rectifier circuit that rectifies the AC output of the photocoupler, a light projecting element that is inserted in a series circuit of the tertiary winding of the first transformer and a primary winding of the second transformer, and light from the light projecting element. A fourth photocoupler including a light receiving element for receiving a signal,
A fourth rectifier circuit that rectifies the AC output of the fourth photocoupler and superimposes the rectified output of the third rectifier circuit on the rectified output, and the AC output extracted by the tertiary winding of the second transformer A rectifying circuit for rectifying the above, an AND circuit for generating an output when each output level of the fourth and fifth rectifying circuits is higher than each preset threshold level, and an output from the AND circuit. The ground detection device according to claim 3, wherein the ground detection device comprises a fourth light emitting diode that is turned on.