JP2008298524A - Circuit testing device and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve measurement accuracy when measuring a low circuit impedance of a circuit to be tested through a contact switching means. <P>SOLUTION: The circuit testing device includes a contact switching means closing during a low-voltage test between the circuit to be tested 1 and a low-voltage inspection circuit 4 and a contact refresh energization circuit 10 applying a preliminary voltage of a sufficient level for breaking down a contact oxide film of the contact switching means. The preliminary voltage is applied between the contacts of a relay 3 for breaking down an insulating film on a surface of the contact of the relay 3 immediately before measuring resistance r of the circuit to be tested 1 through the relay 3 as the contact switching means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a circuit test apparatus for applying a low voltage to a circuit under test to test its electrical characteristics, and in particular, a circuit test apparatus in which a contact switching means is provided in a current path through which a test current flows by the low voltage test. And its operation method.

  For example, for a circuit under test such as a stator coil of a motor, after the manufacture is completed, a high test voltage is applied to check the dielectric strength (current) and a low test voltage is applied to the circuit under test. At least a resistance test is performed to check whether the resistance value of the stator coil, which is a very small resistance value, is within the allowable range of the reference. This type of electrical property test such as withstand voltage and internal resistance is widely performed in various electric and electronic circuit devices in addition to motor coils. Since a circuit under test such as a motor coil has a very small internal resistance, a low test voltage is adopted for the resistance test. That is, in many electrical and electronic device tests, a high voltage test using a high voltage and a low voltage test using a low voltage are performed.

  In some cases, a contact switching means such as a relay or a switch is interposed between a low voltage test circuit for performing such a low voltage test and the circuit under test. In some cases, the circuit under test itself has such contact switching means in series with the circuit portion to be measured.

In a contact opening / closing means such as a relay or switch, an insulating film may be formed on the contact surface due to natural oxidation or corrosion. An example of forming an insulating film on the contact of such a contact opening / closing means is described in Patent Document 1 below.
JP 2002-277494 A

  However, when a small circuit impedance is measured through the contact switching means, the resistance of the electrically insulating film formed on the contact surface of the contact switching means is connected in series, and the circuit impedance to be measured cannot be measured accurately. There was a problem.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a circuit test apparatus capable of accurately measuring a low circuit impedance through a contact switching means and an operation method thereof.

  A first invention that achieves the above object is a test for inspecting the electrical characteristics of the circuit under test by applying a low test voltage at a level at which the insulation film on the contact surface cannot be sufficiently destroyed to the circuit under test. A low voltage inspection circuit for performing a voltage test, a contact opening / closing means provided between the circuit under test and the low voltage inspection circuit, which is closed during the low voltage test, and a contact oxide film of the contact opening / closing means is destroyed. And a contact refresh energizing circuit for applying a reserve voltage of a sufficient level to the contact opening / closing means before the low voltage test.

  According to the present invention, before applying a low test voltage to the circuit under test through the contact switching means from the low voltage inspection circuit and measuring the small circuit impedance of the circuit under test, the contact refresh energizing circuit A preliminary voltage is applied to the contact of the switching means. This reserve voltage is sufficiently large and time to sufficiently break down the insulation film (usually an oxide film) on the contact surface. Therefore, the contact resistance of the contact is sufficiently smaller than the circuit impedance of the circuit under test and its fluctuation is small. Decrease to value. In this way, when a low test voltage is subsequently applied to the circuit under test, the contact voltage drop is sufficiently small, and the low circuit impedance to be measured can be accurately measured.

  In a preferred aspect, the contact opening / closing means comprises a switch or a relay for disconnecting the low voltage test circuit from the circuit under test when a high test voltage higher than the low test voltage is applied to the circuit under test. .

  In this way, a high voltage for, for example, a dielectric strength test can be applied to the circuit under test without completely removing the low voltage inspection circuit from the circuit under test by opening the contact switching means. .

  In a preferred aspect, the contact refresh energization circuit applies the preliminary voltage to the contact opening / closing means through the circuit under test before the low voltage test.

  That is, in this aspect, the preliminary voltage is applied to the contact of the contact switching means through the low circuit impedance of the circuit under test. In this way, the circuit configuration can be greatly simplified.

  In a preferred aspect, the contact refresh energizing circuit applies the preliminary voltage to the contact opening / closing means without going through the circuit under test before the low voltage test. In this way, since it is not necessary to pass a current due to the reserve voltage to the circuit under test, the internal circuit of the circuit under test may be in an interrupted state.

  According to a second aspect of the present invention that achieves the above object, the low test voltage at a level that does not sufficiently destroy the insulating film on the contact surface of the contacted switching means is provided for the circuit under test having the contacted switching means. A low voltage test circuit for performing a low voltage test, which is a test for inspecting the electrical characteristics of the circuit under test by applying through the contact of the contact switching means, and a level sufficient to destroy the contact oxide film of the contact switching means And a contact refresh energizing circuit for applying the preliminary voltage to the contact opening / closing means before the low voltage test.

That is, according to the present invention, a low test voltage is applied to a circuit under test having a built-in contact opening / closing means through a contact of the contact opening / closing means, and electrical characteristics such as circuit impedance of the circuit under test are measured in advance. The contact refresh energization is performed by applying a preliminary voltage having a level and time sufficient to break the insulating film of the contact of the contact switching means to the contact switching means. In this way, it is possible to accurately measure the circuit impedance of the circuit under test incorporating the contact opening / closing means by the same action as described above. After turning on before applying the preliminary voltage, this turning on is continued until the end of the low test voltage. If it does in this way, the change of the contact contact resistance of a contact opening / closing means can be reduced, and the measurement precision of a low voltage test | inspection can be improved.

  In addition, by turning on the contact opening / closing means during the preliminary voltage application and continuing this ON until the end of the low test voltage, the change in contact contact resistance of the contact opening / closing means can be reduced, The measurement accuracy of the low voltage inspection can be improved.

  A preferred embodiment of the present invention will be described below.

(Embodiment 1)
(Circuit configuration)
FIG. 1 is a block circuit diagram for explaining the circuit test apparatus according to the first embodiment. 1 is a circuit under test, 2 is a circuit test apparatus, 3 is a relay (contacted switching means), and the relay 3 is connected to the terminal 21 on the high potential side of the circuit test apparatus 2 and the circuit under test 1 through lines 5 and 6. A terminal 11 on the high potential side is connected. The terminal 22 on the low potential side of the circuit test apparatus 2 is directly connected to the terminal 12 on the low potential side of the circuit under test 1 by the line 7. The low potential side terminal 22 of the circuit test apparatus 2 and the low potential side terminal 12 of the circuit under test 1 may be connected through a relay similar to the above. A switch may be used in place of the relay 3.

  The circuit test apparatus 2 includes a low voltage test circuit 4 that applies a low test voltage of, for example, less than 3 V between terminals 21 and 22 and measures the internal resistance r of the circuit under test 1 through the relay 3, and a diode 9 at the terminal 21. And a contact refresh energizing circuit 10 for applying a preliminary voltage of 24 to 36V. The contact refresh energizing circuit 10 can be, for example, a constant voltage circuit or a constant current circuit, and is a circuit that can intermittently output a preliminary voltage by a manual switch input or some signal.

(Operation)
The operation of this circuit test apparatus 2 will be described below.

  Before outputting the low test voltage from the low voltage inspection circuit 4 and measuring the internal resistance r of the circuit under test 1 by the low voltage inspection circuit 4, the contact refresh energizing circuit 10 includes the fixed contacts 31, 32 of the relay 3 and A preliminary voltage which is a DC voltage (for example, 24 to 36 V) having a time and magnitude sufficient to break down the insulating film on the surface of the movable contact is output to the terminal 21 through the diode 9. At this time, the relay 3 is turned on. As a result, a current flows from the contact refresh energizing circuit 10 to the ground through the diode 9, the terminal 21, the relay 3, and the internal resistance r of the circuit under test 1. Since the internal resistance r and the wiring resistance of this current path are small, most of the reserve voltage is applied to the contact contact resistance of the relay 3, the insulation film on the surface of the closed contact is broken down, and the contact resistance of the relay 3 is It decreases and becomes a stable value.

  Next, a low test voltage is output from the low voltage inspection circuit 4, and the internal resistance r of the circuit under test 1 is measured by the low voltage inspection circuit 4. At this time, the relay 3 is turned on.

  The relay 3 is turned on before energization of the reserve voltage. However, it is very preferable that the relay 3 is turned on when the next low test voltage is applied to the circuit under test 1. In this case, since the contact state of the relay 3 does not change compared to when the relay 3 is turned off once after completion of the preliminary voltage and then turned on again before the low test voltage is applied, the contact contact resistance value of the relay 3 changes. There are few and it can be set as a small value.

(Modification)
In the above embodiment, the reserve voltage is DC 24 V and 0.3 seconds, but the voltage value and energization time can be set as appropriate. Further, instead of a DC voltage, an alternating voltage waveform or a high-frequency pulse voltage waveform may be used.

(Modification)
In the above embodiment, the relay 3 is turned on before energization of the reserve voltage. However, the relay 3 may be turned on while the reserve voltage is applied. In this case, at the moment when the relay 3 is turned on, the insulation film on the contact surface is broken down, and the contact resistance of the relay 3 is reduced and becomes a stable value. Also in this case, it is very preferable that the next low test voltage is applied to the circuit under test 1 while the relay 3 is turned on.

(Modification)
In the above embodiment, the low test voltage is applied to the circuit under test 1 from the low voltage inspection circuit 4 through the relay 3, but instead, the low voltage generated inside the circuit under test 1 may be measured.

(Modification)
In the above embodiment, the circuit test apparatus 2 measures the internal resistance r of the circuit under test 1, but it is natural that the circuit impedance of the circuit under test 1 including the resistance value can be measured.

(Modification)
In the above embodiment, the diode 9 reduces the output voltage of the contact refresh energization circuit 10 when the test is performed by the low voltage inspection circuit 4, and the diode 9 interrupts it. Of course, the reserve voltage may be cut off by using an opening / closing means such as a transistor, a switch or a relay instead of the diode 9. In FIG. 1, when applying the preliminary voltage to the contact of the relay 3, it is natural that the contact of the relay 3 should be controlled to be closed.

(Modification)
Another modification will be described with reference to FIG.

  In FIG. 2, the relay 3 that connects the circuit under test 1 and the circuit test apparatus 2 is omitted, but the circuit under test 1 includes a relay (which may be a switch) 8 in series with the internal resistance r. The circuit test apparatus 2 applies a preliminary voltage to the relay 8 and measures the internal resistance r of the circuit under test 1 through the relay 8. Even in this case, the contact refresh of the relay 8 can be performed by energization of the reserve voltage similar to that of the first embodiment shown in FIG. 1, so that the subsequent measurement of the internal resistance r can be performed accurately.

  In FIG. 2, when applying the preliminary voltage to the contact of the relay 8, it is natural that the contact of the relay 8 should be controlled to be closed. Similarly, in the subsequent measurement of the internal resistance r, the relay 8 is naturally controlled to be closed.

(Modification)
A modification will be described with reference to FIG.

  The circuit under test 1 and the circuit test apparatus 2 are connected through relays 3 and 30, and the circuit test apparatus 2 measures the internal resistance r of the circuit under test 1 through the relays 3 and 30. The contact refresh energization circuit 10 is connected to the relays 3 and 30 through the switches 51 to 54 so that the preliminary voltage Vp can be applied. The switches 51 to 54 can be replaced with relays or the like. Also in this mode, first, the preliminary voltage Vp is energized for a predetermined time between the closed contacts of the relay 3 and between the closed contacts of the relay 3 and between the closed contacts of the relay 30 to destroy the insulating film on the contact surface. Thereafter, the switches 51 to 54 are opened to output a low test voltage from the circuit test apparatus 2 to perform a low voltage test of the circuit under test 1. Even if it does in this way, there can exist an effect similar to the above. Further, after closing the switches 51 to 54, the relay 3 and the relay 30 are closed to destroy the insulating film on the contact surface, and then the switches 51 to 54 are opened to output a low test voltage from the circuit test apparatus 2. Thus, even if a low voltage test is performed on the circuit under test 1, the same effects as described above can be obtained.

(Embodiment 2)
A test of a three-phase stator coil of a motor to which the circuit shown in FIG. 1 is applied will be described with reference to FIG.

(Circuit configuration)
FIG. 4 is a block circuit diagram for explaining the circuit test apparatus according to the second embodiment. Reference numeral 100 denotes a three-phase stator coil of a motor, which includes phase coils 101 to 103 that are star-connected. A circuit test apparatus 200 includes a low-voltage circuit test apparatus 201, a high-voltage circuit test apparatus 202, and a switching relay circuit 300 that form a low-voltage test circuit referred to in the present invention.

  The switching relay circuit 300 includes relays 301 to 303 that individually connect the three measurement terminals of the low-voltage circuit test apparatus 201 and the three terminals of the three-phase stator coil, and the three measurements of the high-voltage circuit test apparatus 202. It consists of relays 304 to 306 that individually connect the terminal and the three terminals of the three-phase stator coil. It is obvious that three changeover switches may be used instead of the relays 301 to 306.

(Operation)
First, a low voltage application test by the low voltage circuit test apparatus 201 will be described.

  The relays 301 to 303 are turned on, the relays 304 to 306 are turned off, and the relays 301 to 303 are passed through the phase coils 101 to 103 from the contact refresh energizing circuit (see FIG. 1) built in the low voltage circuit test apparatus 201. A preliminary voltage is applied between the contacts.

  More specifically, first, only the relays 301 and 302 are turned on to apply a reserve voltage between the relays 301 and 302, and then only the relays 302 and 303 are turned on to apply a reserve voltage between the relays 302 and 303. Finally, the relays 301 and 303 are turned on, and a preliminary voltage is applied between the relays 301 and 303.

  As a result, first, the contacts of the relays 301 and 302 are refreshed, then the contacts of the relays 302 and 303 are refreshed, and finally the contacts of the relays 301 and 303 are refreshed. In this embodiment, since the two relay contacts are refreshed in a serial connection state, the magnitude of the reserve voltage and the energization time are set to values sufficient for the insulation film breakdown on the surfaces of these two relay contacts. In addition, it is advantageous to use a plurality of pulse voltages as the reserve voltage because the breakdown of the insulating film can be promoted while preventing an excessive increase in the contact temperature. The same effect can be obtained by defining the contact current by the preliminary voltage instead of defining the voltage value of the preliminary voltage.

  Next, the relays 301 to 303 are sequentially turned on and off in the same order as described above, and a predetermined low voltage is sequentially applied between the phase coils 101 to 103 of the three-phase stator coil 100 from the low voltage test circuit of the low voltage circuit test apparatus 201. The three interphase coil resistance values are measured.

  Next, the relays 301 to 303 are turned off, the relays 304 to 306 are turned on, and a predetermined high test voltage is applied to the phase coils 101 to 103 from the high voltage circuit test apparatus 202 to perform various high voltage tests. Since the high voltage test itself is not the gist of this embodiment, a detailed description is omitted. In one example, the high voltage circuit test apparatus 202 applies a high voltage such as 1950 V between the phase coils 101 to 103 and the ground through the relays 304 to 306. Thereby, the insulation resistance value of the phase coils 101-103 can be calculated | required. In addition, the high-voltage circuit test apparatus 202 can apply an AC voltage or a pulse voltage to the phase coils 101 to 103 through the relays 304 to 306 and measure the stray capacitance of the three-phase stator coil 100 from the current.

  The relays 301 to 306 are high-voltage relays that can cut off the high voltage without any problem, but may be manual changeover switches.

  According to this embodiment, the low voltage circuit test and the high voltage circuit test can be sequentially performed in a state where the three terminals of the single circuit test apparatus 200 are connected to the three terminals of the three-phase stator coil 100. The apparatus can be simplified and the work can be simplified.

  In this embodiment, the insulating film at the contact portion between the three terminals of the three-phase stator coil 100 and the tip terminals of the three measurement cables of the circuit test apparatus 2 is also refreshed by the contact refresh energization, so that further measurement is performed. Accuracy can be improved.

  Fig. 5 shows the change over time in the measured value of inter-phase coil resistance when pre-energization for contact refresh is not performed. Immediately after pre-energization for contact refresh, the inter-coil resistance is measured with a low-voltage inspection circuit. FIG. 6 shows the change over time of the measured value in the case of the measurement. As can be seen from FIGS. 5 and 6, it can be seen that the temporal change in the resistance value between the phase coils during the measurement period is remarkably improved by the preliminary energization described above.

(Modification)
In the above embodiment, the relays 301 to 303 are turned on / off to change the path of the pre-energization current during the pre-energization period, and the relays 301 to 303 are also changed before the current path is changed in the subsequent low voltage test for measuring the resistance between the phase coils. Although 303 is turned on / off, such on / off of the relays 301 to 303 may cause a change in the contact state.

  Therefore, the relays 301 to 303 may be turned on all at once before the start of pre-energization, and the relays 301 to 303 may be kept on until the low voltage application test after the pre-energization is completed. The above-described current switching at this time can be easily performed by the current switching circuit in the low-voltage circuit test apparatus 201.

  Alternatively, the relays 301 to 303 may be turned on all at once during the preliminary energization, and the relays 301 to 303 may be kept on until the low voltage application test after the preliminary energization is completed.

(Modification)
The contact refresh effect described above is further improved when the relays 301 to 303 are intermittently connected a predetermined number of times in a state in which a preliminary voltage is applied to the relays 301 to 303. Such a circuit for switching the relays 301 to 303 is easily designed, and thus a detailed description thereof is omitted.

1 is a block circuit diagram of an apparatus for explaining Embodiment 1. FIG. FIG. 6 is a block circuit diagram of an apparatus for explaining a modification of the first embodiment. FIG. 6 is a block circuit diagram of an apparatus for explaining a modification of the first embodiment. FIG. 6 is a block circuit diagram of an apparatus for explaining a second embodiment. It is a figure which shows the change of the resistance detection value when not carrying out preliminary electricity supply. It is a figure which shows the change of the resistance detection value in the case of carrying out preliminary electricity supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit under test 2 Circuit test apparatus 3 Relay 4 Low voltage test circuit 8 Relay 9 Diode 10 Contact refresh energization circuit 30 Relay 51-54 Switch 100 Phase stator coil 101-103 Phase coil 200 Circuit test apparatus 201 Low voltage circuit test Device 202 High Voltage Circuit Testing Device 300 Relay Circuit 301 Relay 301-306 Relay

Claims (7)

A low voltage test circuit for performing a low voltage test, which is a test for inspecting the electrical characteristics of the circuit under test by applying a low test voltage at a level at which the insulation film on the contact surface cannot be sufficiently destroyed to the circuit under test;
Contacted switching means provided between the circuit under test and the low-voltage test circuit and closed during the low-voltage test;
A contact refresh energization circuit for applying a preliminary voltage at a level sufficient to destroy the contact oxide film of the contact switching means to the contact switching means before the low voltage test;
A circuit test apparatus comprising: The circuit test apparatus according to claim 1,
The circuit test apparatus comprising a switch or a relay for disconnecting the low voltage test circuit from the circuit under test when the contact switching means applies a high test voltage higher than the low test voltage to the circuit under test. The circuit test apparatus according to claim 1,
The contact refresh energization circuit applies the preliminary voltage to the contact opening / closing means through the circuit under test before the low voltage test. The circuit test apparatus according to claim 1,
The contact refresh energization circuit applies the preliminary voltage to the contact switching means without going through the circuit under test before the low voltage test. A low test voltage at a level that does not sufficiently destroy the insulating film on the contact surface of the contact switching means is applied to the circuit under test having the contact switching means through the contact of the contact switching means. A low voltage inspection circuit for performing a low voltage test, which is a test for inspecting the electrical characteristics of the test circuit, and
A contact refresh energization circuit for applying a preliminary voltage at a level sufficient to destroy the contact oxide film of the contact switching means to the contact switching means before the low voltage test;
A circuit test apparatus comprising: In the operation method of the circuit test apparatus according to any one of claims 1 to 5,
The circuit test apparatus operating method in which the contact opening / closing means is turned on before the preliminary voltage is applied, and is kept on until the low test voltage ends. In the operation method of the circuit test apparatus according to any one of claims 1 to 5,
The circuit test apparatus operating method, wherein the contact opening / closing means is turned on while the preliminary voltage is applied, and is kept on until the end of the low test voltage.

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