JPH0125332Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an insulation resistance measuring device that can safely and reliably measure the insulation resistance of a DC electric circuit under use in a short period of time. Conventionally, the insulation resistance of a DC electric circuit has been measured by turning off the power to a device including the electric circuit and measuring it with a resistance meter in a no-voltage state. However, in recent years, as the systemization of various devices has progressed, it is preferable to stop the electrical circuit, which is the central element, every time an insulation resistance measurement is performed, as this would involve stopping the entire system. do not have. Therefore, the present inventor invented a method that can quickly measure the insulation resistance of a DC electric circuit under voltage application (Japanese Patent Application No. 3480/1983). In this method, two replacement resistors with different resistance values are inserted switchably between an arbitrary measurement point in a DC electric circuit and the ground electrode, and the leakage voltages e ₁ and e ₂ of the circuit in which each resistor is inserted are calculated. The insulation resistance of the DC electric circuit is determined from the deviation values. However, this method actually involves calculating the deviation coefficient based on the measured voltage between two measurement points, and determining the insulation resistance value of the electric circuit from the conversion curve. reading the measured voltage,
This involves calculating the deviation coefficient and converting using a conversion curve. The present invention aims to expand the popularity of the above method by simplifying it, and a scale film on which the insulation resistance corresponding to the leakage voltages e ₁ and e ₂ is drawn as a curved line is attached in advance to the voltmeter so that it can be displaced. Therefore, the insulation resistance of the DC electric circuit to be measured can be directly read at a glance, thereby eliminating the need for reading the measured voltage, calculating the deviation coefficient, and converting using a conversion curve, as well as eliminating the need for the replacement resistance circuit and voltage measurement range. The aim is to expand the measurement range of insulation resistance and improve accuracy by providing multiple defined voltage dividers in parallel. The present invention will be explained according to the embodiments shown in FIGS. 1 to 4. Reference numerals 2 and 2 indicate measurement terminals, and measurement points of the DC electric circuit to be measured are connected to the measurement terminals 2 and 2. Replacement resistors R ₁ group and R ₂ group are connected in parallel to measurement terminals 2 and ₂ via changeover switches SW ₁ and SW 2. The switch SW ₁ is a switch for switching between the replacement resistors R ₁ group and R ₂ group, and the switch SW ₂ switches between the resistor R ₁ ′ of the R ₁ group and the resistor R ₂ ′ of the R ₂ group, and the resistor R ₁ ″. _R2 ″…
...This is a switch for switching between resistor R ₁ ⁿ and resistor R ₂ ⁿ . The resistance value of each resistor above is R ₁ ′: R ₂ ′= R ₁ ″: R ₂ ″=
It is set as R ₁ :R ₂ =R ₁ ⁿ :R ₂ ⁿ . A DC voltage measuring circuit indicated as 1 surrounded by a dotted line is connected in parallel to the above circuit. r ₁ ~ _{r o} is a switch
It is a voltage divider switchable by SW ₃ and V ₁ is a voltmeter. Note that r is the insulation resistance of the DC electric circuit to be measured, and D is a dial knob for displacing the scale film. From the state shown in Figure 1, by turning switch SW ₁ to R ₁ side, the leakage voltage appearing on voltmeter V ₁ is e ₁ ,
Assuming that the leakage voltage that appears on the voltmeter V ₁ by turning it to the R ₂ side is e ₂ and that the internal resistance of the DC voltage measurement circuit 1 is infinite, the difference coefficient n of e ₁ and e ₂ is given by the following formula. expressed. n=e ₁ /e ₂ =R ₁ (r+R ₂ )/R ₂ (r+R ₁ )...(1) Insulation resistance r is expressed by the following formula. r=(n-1)R ₁ /R ₁ /R ₂ -n ...(2) For convenience of explanation, in the R ₁ resistance group, replacement resistance
R ₁ ″, and for the R ₂ resistance group, select the replacement resistor R ₂ ″,
Assuming that R ₁ ″ is 11MΩ, R ₂ ″ is 1MΩ, and the voltage measurement range of DC voltage measurement circuit 1 is 30V, which is determined by the selection of voltage divider r ₁ to r _o ^{1 ′} of switch SW ₃ . The difference coefficient n corresponding to the insulation resistance r of the measured electric circuit and the value e ₁ corresponding to the leakage voltage e ₂ are the third
As shown in the diagram. FIG. 4 shows the scale film 3 on which the insulation resistance r corresponding to the leakage voltages e ₁ and e ₂ in FIG. 3 is drawn as a curve. The insulation resistance r in this scale film 3 is obtained from e ₁ and e ₂ when the measurement range is 30V, but R ₁ ′ to R _{1 of the resistance group R 1}
Since the selected combinations of R ₁ ⁿ and R ₂ ′ to R ₂ ⁿ of R ₂ of the resistance group R ₂ and their respective resistance values are set as described above, the internal resistance of the DC voltage measurement circuit 1 remains unchanged. Since the deviation coefficient n is always constant as long as it is, we can calculate the value of insulation resistance r from the same scale film.
It can be read as a multiplier of the set resistance value of the combined replacement resistance of _R1 group and _R2 group. If the resistance value of R ₁ ′ is 22MΩ and that of R ₂ ′ is
2MΩ, r is 18MΩ, n = 5.5, and the resistance value of R ₁ ″ is 11MΩ, that of R ₂ ″ is 1MΩ, r is 9MΩ, then from equation (1), n = 5.5, the resistance value of R ₁ 1.1MΩ,
If that of R ₂ is 0.1MΩ and r is 0.9MΩ, then n
=5.5 and if the ratio of the resistance values of R ₁ and R ₂ is constant, n is always constant. Furthermore, when the numerical values in the three cases mentioned above are substituted into equation (2), in the first case, r=
18 MΩ, in the second case r=9 MΩ, and in the third case r=0.9 MΩ, where r is expressed as a multiplier of the set resistance values of R ₁ and R ₂ . Therefore, by setting the specifications as shown in Table 1, for example, it is possible to expand the measurement range of insulation resistance and improve its accuracy.

[Table] As shown in FIG. 2b, the scale film 3 shown in FIG. Attach to the back side of ₁ . One side,
An arc-shaped peephole 8 is formed in the scale plate 7 of the voltmeter _V1 along the arc in which the indicator 9 swings, so that the curved part r indicating the insulation resistance of the scale film 3 can be read directly from the front. In this case, the scale plate 7 of the voltmeter _V1 forms the above-mentioned peephole 8 so that it can be used as is. In such a configuration, first, according to the expected measured voltage e ₁ of the electric circuit to be measured, an appropriate voltage divider from r ₁ to _{r o} is selected by switch SW ₃ , and the expected measured insulation resistance value is selected. follow r, switch
After selecting an appropriate combination of replacement resistors from the _R1 group and the _{R2 group using SW 2 ,} the measurement points of the electrical circuit to be measured are connected to the terminals 2, 2. In the above case, the measurement voltage range is determined by the voltage divider selected by switch SW ₃ , so it is preferable to select a voltage divider that increases the indication angle of display voltage e ₁ in the sense that measurement accuracy will be higher. Also, the difference in the indicated angles of e ₁ and e 2 is determined by the selection of the combination of replacement resistors of the R ₁ group and R ₂ group by switch SW ₂ , so the difference in the indicated angles of _{e 1 and} e ₂ becomes larger. It is preferable to select as follows for the same reason as mentioned above. After setting as above, when switch SW ₁ is moved to the side of replacement resistor R ₂ group, e ₂ will be displayed on voltmeter V ₁ . Thereafter, by rotating the dial knob D in a predetermined direction, the drive gear 4 is rotated in a predetermined direction, and the scale film 3 is rotated along a part of the outer periphery of the rotating drums 6, 6. The indicated position of the indicator needle 9 and the base line of the insulation resistance of the scale film shown in Fig. 4
When it is confirmed through the peephole 8 that a part of r0MΩ has become heavy, the rotation of the scale film 3 is stopped, and then the switch SW ₁ is switched to the side of the replacement resistor R ₁ group. As a result, _e1 is displayed on the voltmeter _V1 , but at the same time, the indicator needle 9 indicates the insulation resistance of the scale film 3 on the back side of the peephole 8, that is, the insulation resistance of the electrical circuit to be measured. Note that 10 is a line on a transparent plate attached to the peephole 8 and is a reference line for checking the indicator needle 9 and the insulation resistance. According to the present invention, the insulation resistance of a DC electric circuit in use or under voltage application can be determined with an extremely simple configuration without having to perform complicated operations such as reading measured voltage, calculating deviation coefficients, and converting conversion curves. By adding this to general small DC voltmeters, circuit meters, etc., the problems mentioned at the beginning of this book can be easily solved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the invention, Fig. 2a is a front view showing an example of the mechanism of the invention, Fig. 2b is a side view of the indicator section of Fig. 2a, and Fig. 3 is a A chart showing the deviation coefficient corresponding to the insulation resistance of the electrical circuit to be measured and the value of e ₁ against the leakage voltage e _2. Figure 4 is a front view showing the positional relationship between the indicator section and the scale film in Figure 2 a. It is a diagram. 2, 2...Measuring terminal, 3...Graduation film, 8
...Voltmeter peephole, R ₁ , R ₂ ...Replacement resistance, r
... Insulation resistance, r ₁ ~ r _o , SW ₃ ... Voltage measurement range switching circuit, SW ₁ , SW ₂ ... Selector switch, V ₁ ...
DC voltmeter.

Claims (1)

[Scope of utility model registration request] Replacement resistance groups R ₁ and R ₂ , which are resistances having different resistance values connected in parallel, are connected between measurement terminals via changeover switches SW ₁ and SW ₂ , respectively.
Each of the resistors forming one of the above-mentioned replacement resistance groups R ₁ and the corresponding other replacement resistance group
Set the resistance ratio with each resistor that makes up R ₂ to be the same, and turn the above selector switch.
SW ₁ is used to switch between the replacement resistance groups R ₁ and R ₂ , and switch SW ₂ is used to switch between the resistances that make up the replacement resistance group R ₁ and between the resistances that make up the replacement resistance group R ₂ . and set the above selector switch SW ₁
On the negative side of the switch, there is a switch that switches between the resistor group connected in parallel and the resistors that make up the resistor group.
A voltage divider consisting of SW ₃ and then a DC voltmeter are connected, and the changeover switch SW ₁ and SW _{2 provide a replacement resistor group in a voltage measurement range determined by switching between the voltage dividing resistors by the changeover switch SW 3 .} A scale film with a curved line representing the insulation resistance of the electrical circuit to be measured based on the substitution resistance, determined by switching between the resistors composing R ₁ or R ₂ , is hung endlessly between the rotating drums, and a DC voltmeter is measured. The scale plate of the DC voltmeter has an arc-shaped peephole along the arc in which the indicator needle swings, so that the curve indicating the insulation resistance of the scale film 3 can be seen directly from the front of the DC voltmeter. A device for measuring insulation resistance of a DC circuit under operating conditions, configured as follows.