JPH067727B2 - Insulation monitoring device - Google Patents

Description

The present invention relates to a device for monitoring a state in which a line for supplying electric power to medical electrical equipment is semi-insulated from a ground level to prevent electric shock, for example, in a hospital or the like.

The safety standards for such hospital electrical equipment are specified in Japanese Industrial Standards. According to the standard, the secondary output line of the isolation transformer used to supply electric power to medical electrical equipment is a non-grounded line, and the ground impedance of one of the lines decreases, and in this state, another line is grounded. It is stipulated that an alarm be issued when the value of the ground fault current flowing when it is assumed that a fault has occurred is 2 mA or more.

A typical prior art is disclosed in Japanese Utility Model Laid-Open No. 58-118838, which is shown in simplified form in FIG.
Electric power is supplied to the load from the secondary side output lines 92 and 93 of the insulating transformer 91, and the resistors 95 and 9 are connected to the neutral point 94 thereof.
6 is connected and line 97 is grounded. Z1, Z2
Is the ground insulation impedance, the current flowing through the resistor 95 is indicated by i21 and i22, the resistance value of the resistor 95 is R, the voltage across the resistor 95 is V1, and the angular frequency is ω. The formula holds.

V1 = R · i21 · sin (ωt + π) + R · (−i22) · sinωt In the prior art, the voltage V1 of the resistor 95 is detected. This voltage V1 corresponds to the difference between the insulation impedances Z1 and Z2. Therefore, insulation impedance Z1, Z2
Of the same impedance, their insulation impedance Z
If Z1 and Z2 have the same value, insulation impedance Z1,
Despite the deterioration of Z2, it becomes impossible to detect it.

An object of the present invention is to provide an insulation monitoring device capable of surely detecting the deterioration of the two secondary output lines of the insulation transformer even if the ground insulation impedances Z1 and Z2 have the same value. That is.

The present invention comprises: (a) connecting first and second resistors R1 and R2 having the same resistance value in series between the ungrounded secondary side output lines 7 and 8 of the insulating transformer 4, and (b) the first and second resistors R1 and R2. Connection point 3 between the second resistors R1 and R2
The third and fourth resistors R3; VR1 and R4 are connected in series to 0, and (c) the anodes of the pair of first and second diodes D1 and D2 are provided on the opposite side of the fourth resistor R4 from the third resistor R3. (D) The cathodes of the first and second diodes D1 and D2 are connected to the secondary side output lines 7 and 8, respectively. (E) The anode is the fifth resistor R5, VR2 and the sixth resistor in series. It is grounded through the resistors R6 and R36, and (f) the connection point 3 between the third and fourth resistors R3 and R4.
0a and the node 31 between the anodes of the first and second diodes D1 and D2 and the node 31 between them are the reference voltage V11, and the node 34 between the fifth and sixth resistors R5; R6 and R36, and The voltage between the mutual connection point 31 of the anodes of the first and second diodes D1 and D2 is the detection voltage V1.
2, the reference voltage V11 and the detection voltage V1
The insulation monitoring device is characterized by comprising difference detection means 38, 39, 40 for obtaining a difference from 2.

FIG. 1 is an electric circuit diagram of an embodiment of the present invention. Electric power from the commercial AC power supply is applied to the primary winding 5 of the insulating transformer 4 from the lines 1 and 2 through the wiring or the breaker 3. The secondary winding 6 of the insulation transformer 4 is used for wiring from the secondary side output lines 7 and 8 and power is supplied from the medical plug-in connectors 12, 13 and 14 to medical electrical equipment via the disconnectors 9, 10 and 11. Is supplied. The medical grounding center 15 is grounded via a grounding trunk line 16. The insulation state of the secondary side output lines 7 and 8 from the ground level is monitored by the insulation monitoring device 19 according to the present invention. The ground fault current of the secondary side output lines 7 and 8 is
It is displayed by the meter 20. When the ground fault current is less than 2 mA, the normal indicator lamp 21 lights up. When the ground fault current becomes 2 mA or more, the abnormality display lamp 22 is turned on and the buzzer 23 emits an alarm sound. To stop the ringing operation of the buzzer 23, the buzzer stop switch 24 may be operated. The test switch 25 causes a state in which the ground fault current becomes 2 mA or more in the one secondary output line 8 by pressing the test switch 25, whereby the insulation monitoring device 19 operates normally. It was confirmed that it was ready to do.

In the insulation monitoring device 19, when it is detected that the ground fault current is 2 mA or more, and therefore the buzzer 23 sounds, the medical plug-in connectors 12, 13,
Remove the medical electrical devices connected to 14 one by one. When the removed medical electrical equipment has poor insulation,
The ground fault current is, for example, 1.7 mA or less, which automatically stops the buzzer 23 from ringing. If the medical electrical equipment is removed from the medical plug-in connectors 12, 13, 14 and insulation is still in a defective state, the wiring breaker and the disconnectors 9, 10, 11 are shut off one by one to generate a buzzer. Check for automatic stop of ringing 23. In this way, the location of defective insulation can be examined.

FIG. 2 is an electric circuit diagram showing a specific configuration of the insulation monitoring device 19 according to the embodiment of the present invention. Insulation transformer 4-2
A series first resistor R1 and second resistor R2 having the same resistance value are connected between the secondary output lines 7 and 8 connected to the secondary winding 6. First and second resistors R1, R
The mutual connection point 30 of the two is connected to the connection point 3 via the resistor R3.
0a, and further the variable resistor VR1 and the resistor R
4 is connected to the connection point 31 of the anodes of the pair of first diode D1 and second diode D2. The resistor R3 constitutes a third resistor, and the variable resistor VR1 and the resistor R4 constitute a fourth resistor. First and second diodes D1, D
Each cathode 2 is connected to the secondary output lines 7 and 8, respectively. The anode connection point 31 of the first and second diodes D1 and D2 has a resistance R5 and a variable resistance VR2 that form a fifth resistance, and a resistance R that forms a sixth resistance.
6, via R36 to ground from line 32. The connection point 30a is connected to the line 33. The connection point 34 of the resistor R5 and the variable resistor VR2 forming the fifth resistor, and the resistors R6 and R36 forming the sixth resistor is connected to the line 3
Connected to 5.

The insulating impedances between the secondary output lines 7 and 8 and the ground level are equivalently indicated by reference signs Z1 and Z2, respectively. The test switch 25 and the resistor R7 are connected in series and interposed between the line 32 and the secondary output line 8.

The voltage between the lines 33 and 35 is zero when the insulation resistances Z1 and Z2 are substantially infinite. Line 8,
32 conducts through the resistance R7 by the operation of the test switch 25 as described above, and the insulation resistances Z1 and Z2.
Have a certain value different from each other or the same certain value, a connection point 3 with the resistor R3 and the variable resistor VR1.
0a and the connection point 31 as a reference voltage, and the difference between the reference voltage and the detection voltage between the connection point 34 and the connection point 31 is compared by an amplifier circuit 38, 39 described below. 40 to detect.

Smoothing capacitors 36 and 37 are connected between the lines 33 and 35 and the line 71, respectively. Lines 33,3
The output of 5 is amplified by the amplification circuits 38 and 39 of the amplification comparison circuit 61, respectively, and given to the input terminals 41 and 42 of the comparison circuit 40 which is a differential amplification circuit. Comparison circuit 40
Output 43 has a voltage difference between the detected voltage and the reference voltage, and is applied to the meter output circuit 45 via the relay switch S8 of the relay Ry2.

The meter output circuit 45 includes the meter 20 and has an insulation resistance Z.
The output from the comparison circuit 40 through the relay switch S8 is corrected and applied to the meter 20 so that the indicator needle of the meter 20 is angularly displaced by an angular displacement amount that is directly proportional to the sum of the currents flowing in 1 and Z2. The output from the meter output circuit 45 via the line 45a is given to one input terminal 48 of the comparison circuit 47 in the alarm circuit 46. The other input terminal 49 of the comparison circuit 47 has resistors R28 and R29 connected to it.
And a reference voltage determined by the variable resistor VR3. When the voltage applied to the input terminal 48 is equal to or higher than the reference voltage applied to the other input terminal 49 corresponding to the ground fault current of 2 mA or more flowing through the insulation resistances Z1 and Z2, the comparison circuit 47 has a low level. Signal is output to the output line 52. As a result, the transistor 51 becomes conductive. The variable resistor VR8 is connected in relation to the comparison circuit 47, and the voltage at the input terminal 48 is equal to that of the insulation resistors Z1 and Z.
When the voltage corresponding to the current of 1.7 mA flowing in 2 is lowered, the output line 52 is brought to a high level.

The transistor 51 has a relay coil L1 of the relay Ry1.
Are connected in series. The common contact 5 of the relay switch S1 is generated by exciting the relay coil L1.
3 switches from the individual contact 54 to the individual contact 55 during the excitation period of the relay coil L1. In the movable contact 54,
The normal display lamp 21 is connected in series, and the abnormal display lamp 22 is connected to the other movable contact 55.
Further, the relay switch S2 in series with the buzzer 23 becomes conductive by the excitation of the relay coil L1. The buzzer stop switch 24 has its common contact 56 connected to the individual contact 57,
As a result, power is supplied to the buzzer 23 via the relay switch S2, and the buzzer 23 can ring. When the common contact 56 is switched to the other individual contact 58, the buzzer stop display lamp 24a lights up. By connecting the common contact 56 of the buzzer stop switch 24 to the individual contact 58, the yellow buzzer stop indicator lamp 24
a lights up.

The output from the power supply circuit 60 connected to the lines 7 and 8 is
It is given to the amplification comparison circuit 61, the meter output circuit 45, and the alarm circuit 46, and also given to the initial setting circuit 62. The electric power from the power supply circuit 60 is charged by the capacitor 64, and the charging voltage is given to the base of the transistor 65. A connection point 66 with the resistor R34 connected in series with the transistor 65 is given from the Zener diode ZD1 for setting a voltage to the base of the transistor 67 via the resistor R35. Transistor 67
The relay coil L2 of the relay Ry2 is connected in series with the.

When the power is turned on, the base voltage of the transistor 65 is low, and thus the transistor 65 is cut off. At this time, a current flows from the relay coil L2 of the relay Ry2 to the emitter and the base of the transistor 67, the resistor R35 and the broken Zener diode ZD1, and further to the connection point 66 and the resistor R34, so that the transistor 67 becomes conductive. As a result, the relay coil L2 is excited, the common contact 70 of the relay switch S8 conducts to the individual contact 72 and is set to a high level, and the output 43 of the amplification comparison circuit 61 is not input to the meter output circuit 45. Therefore, meter 20 and alarm circuit 4
6 does not malfunction.

After the power is turned on, the voltage of the capacitor 64 gradually rises. When the charging voltage becomes high, for example, 10 seconds after the power is turned on, the transistor 65 becomes conductive for the first time. As a result, the voltage at the connection point 66 rises, and no current flows from the emitter to the base in the transistor 67. Therefore, the transistor 67 is cut off and the relay coil L2 is cut off. Accordingly, the common contact 70 of the switch S8 is brought into conduction with the individual contact 71 connected to the output 43 of the amplification / comparison circuit 61, and enters the insulation monitoring state.

FIG. 3 is a simplified electric circuit diagram for explaining the operation of the embodiment of the present invention shown in FIGS. 2, 2A and 2B. Lines 33, 3 at connection points 30a, 34
Comparing circuit 40 of amplification comparing circuit 61 connected via 5
The voltage detected by is related to a total of two voltages, that is, the voltage V11 between the connection points 30a and 31 and the voltage V12 between the connection points 34 and 31, and the voltage V11 between the connection points 30a and 31 is used as a reference. Voltage and the voltage V between the connection points 34 and 31
12 as the detection voltage, and the reference voltage V11 and the detection voltage V12
By giving a difference between the reference voltage V11 and the detection voltage V11 to the comparison circuit 40 which is a differential amplifier circuit,
An output obtained by amplifying the difference of 12 is obtained.

V12 = (R5 + VR2) .i13.sin (.omega.t + .pi.) + (R5 + VR2) .i14.sin.omega.t This output 43 is given to the meter output circuit 45 and the meter 20
To operate. The variable resistors VR1 and VR2 are provided to correct the errors of the fixed resistors R1 to R4; R5, R6 and R36.

When the insulation impedance Z1 is lowered and the other insulation impedance Z2 is extremely large, the output is output via the output line 7, the insulation impedance Z1, the resistance R36, the resistance R6, the variable resistance VR2, the resistance R5, the connection point 31, and the diode D2. A current flows through line 8. Connection point 3
0a, 31 between the reference voltage V11 and connection points 34, 31
The difference between the detected voltage V12 and the detected voltage V12 does not change depending on the fluctuation of the voltage between the output lines 7 and 8, but when the insulation impedance Z1 decreases as described above, the current i13 (the above-mentioned third (See the figure), the difference between the reference voltage V11 and the detected voltage V12 is amplified by the comparison circuit 40 and given to the meter output circuit 45 to operate the meter 20 as described above. When the ground fault current increases in this way, the lines 33,
The voltage across 35 rises and accordingly the output 43 of the comparison circuit 40
Voltage drops. The voltage of the output 43 corresponding to this ground fault current is given from the switch S8 to the meter output circuit 45, and the ground fault current is displayed by the meter 20.

When the ground current becomes 2 mA or more, the output line 52 of the comparison circuit 47 of the alarm circuit 46 becomes low level, the transistor 51 becomes conductive, and the relay coil L1 is excited. Therefore, the common contact 53 of the switch S1 conducts to the common contact 55, the abnormality display lamp 22 lights up, and the power supplied from the common contact 56 of the buzzer stop switch 24 through the individual contact 57 by conduction of the relay switch S2. Sounds the buzzer 23. This abnormal state is caused by the relay Ry1.
Another relay switch S5, which is made conductive by the relay coil L1 of FIG.
It is transmitted from 8,69 to a remote place. To stop the ringing state of the buzzer 23, the common contact 56 of the buzzer stop switch 24 may be switched to the movable contact 58. The buzzer stop indicator lamp 2 is provided on the pressing operation portion of the buzzer stop switch 24.
The built-in 4a facilitates handling.

As described above, according to the present invention, the third and fourth resistors R
3; Mutual connection point 30a of VR1 and R4 and mutual connection point 3 of anodes of the first and second diodes D1 and D2
The voltage between 1 and 5 is the reference voltage V11, and the fifth and sixth
Resistance R5, VR2; R6, R36 mutual connection point 34
And the voltage between the mutual connection point 31 of the anodes of the first and second diodes D1 and D2 is the detection voltage V12, the reference voltage V11 and the detection voltage V12 are the secondary side output of the isolation transformer 4. When the voltage between the lines 7 and 8 changes, it changes, but these reference voltage V11 and detection voltage V
12 is offset by determining the difference between the reference voltage V11 and the detected voltage V12 by the difference detection means 38, 39, 40, and thus the difference is output. , 8 does not depend on the change in voltage,
It changes according to the deterioration of the insulation impedance Z1, Z2,
That is, when the ground fault current increases, it changes significantly, and when the insulation impedances Z1 and Z2 of the two secondary output lines 7 and 8 have the same value and the insulation impedances Z1 and Z2 decrease, and Even when these insulation impedances Z1 and Z2 are different from each other and the insulation impedances Z1 and Z2 decrease, the current flowing through the fifth resistors R5 and VR2 increases and the detection voltage V12 increases. Thus, the difference between the reference voltage V11 and the detection voltage V12 of the fifth resistors R5 and VR2 can be detected by the difference detecting means 38, 39 and 40, and thus the insulation impedances Z1 and Z2 are the same. It is possible to reliably monitor the insulation state even when the values decrease or when the values differ from each other.

[Brief description of drawings]

FIG. 1 is an overall electric circuit diagram of an embodiment of the present invention, and FIG. 2 shows a state in which FIGS. 2A and 2B are combined. FIG. 2A is a specific electrical circuit diagram showing a part of the specific electrical configuration of the insulation monitoring device 19 according to one embodiment of the present invention, and FIG. 2B is a specific configuration of the insulation monitoring device 19. FIG. 3 is an electric circuit diagram showing the remaining portion showing a simple electrical configuration, FIG.
FIG. 4 is a simplified electrical circuit diagram for explaining the operation of the embodiment shown in FIGS. 2, 2A and 2B, and FIG. 4 is a prior art electrical circuit diagram. 4 ... Isolation transformer, 7, 8 ... Secondary output line, 19 ... Insulation monitoring device, R1 ... 1st resistance, R2 ... 2nd resistance, D1 ...
1st diode, D2 ... 2nd diode, Z1, Z2 ...
Insulation resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 56-126126 (JP, U) Rib 57-114978 (JP, U) Rib 58-118838 (JP, U)

Claims (1)

[Claims] (A) First and second resistors R1 and R2 having the same resistance value in series are connected between the ungrounded secondary side output lines 7 and 8 of the insulating transformer 4, and (b) the first And a connection point 3 between the second resistors R1 and R2.
The third and fourth resistors R3; VR1 and R4 are connected in series to 0, and (c) the anodes of the pair of first and second diodes D1 and D2 are provided on the opposite side of the fourth resistor R4 from the third resistor R3. (D) The cathodes of the first and second diodes D1 and D2 are connected to the secondary side output lines 7 and 8, respectively. (E) The anode is the fifth resistor R5, VR2 and the sixth resistor in series. It is grounded through the resistors R6 and R36, and (f) the connection point 3 between the third and fourth resistors R3 and R4.
0a and the node 31 between the anodes of the first and second diodes D1 and D2 and the node 31 between them are the reference voltage V11, and the node 34 between the fifth and sixth resistors R5; R6 and R36, and The voltage between the mutual connection point 31 of the anodes of the first and second diodes D1 and D2 is the detection voltage V1.
2, the reference voltage V11 and the detection voltage V1
An insulation monitoring device comprising difference detection means 38, 39, 40 for obtaining a difference from 2.