A device and method for quickly measuring the insulation resistance of a conductive slip ring

Abstract

The present invention discloses a device and method for rapidly measuring the insulation resistance of a conductive slip ring. The device includes a sampling resistor, a current-limiting resistor, a first switch matrix and a second switch matrix each containing a plurality of single-pole single-throw switches, a high-voltage excitation source, a voltage sampling unit, and a control unit. When using this device to test a conductive slip ring, first, the insulation resistance of each tap relative to the short-circuit points of all other taps is tested to preliminarily narrow down the range of the defect location; then, the dichotomy principle is used to quickly locate the defective tap combination. The present invention can effectively reduce the time required for testing a single conductive slip ring and improve the product detection efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of test instruments, and particularly relates to a device and method for rapidly measuring the insulation resistance of a conductive slip ring. Background Art

[0002] A conductive slip ring is an electrical product used for electrical connection of a relatively rotating structure to solve the problem of wire winding during unrestricted rotation. There are many types of conductive slip rings, including through-hole conductive slip rings, cap-type conductive slip rings, micro conductive slip rings, Ethernet conductive slip rings, direct plug-in conductive slip rings, etc., which are widely used in multiple fields and industries such as security, power, and instruments.

[0003] Generally, several to dozens of slip rings are installed on a cylindrical insulating material on a conductive slip ring device. The insulation strength between the slip rings has an important impact on its voltage withstand performance. Short circuits between slip rings and defects in slip ring materials, such as cracks and holes during potting, may all lead to a decrease in the insulation performance of the conductive slip ring device. To detect the insulation resistance or voltage withstand ability of a conductive slip ring product, traditionally, an insulation resistance tester or an insulation voltage withstand tester is used to test the insulation impedance between each ring. During the test, the tester is connected to the tap heads of the two slip rings to be tested, and a voltage is applied between the two rings according to the voltage withstand index requirements of the product. In this case, the insulation resistance between the two rings is measured, and this insulation resistance value should be greater than the specified value (such as 10 MΩ). For a device with multiple slip rings, the insulation resistance between each two slip rings should meet the requirements.

[0004] With the development of technology, currently, the number of rings of a conductive slip ring device can reach dozens to hundreds. However, the increase in the number of rings leads to an exponential increase in the number of tap combinations that need to be detected. For example, a 10-ring conductive slip ring only needs to test sets of insulation resistance values, while a 100-ring conductive slip ring needs to test sets of insulation resistance values. The sharp increase in the test volume results in a decrease in the test efficiency of the conductive slip ring, ultimately affecting the production efficiency. Summary of the Invention

[0005] Aiming at the problem in the prior art that the insulation resistance values between all tap heads of a conductive slip ring cannot be obtained quickly and efficiently, the present invention provides a device and method for rapidly measuring the insulation resistance of a conductive slip ring.

[0006] The device involved in the present invention includes sampling resistors and current-limiting resistors equal in number to the number N of slip ring tap heads, a first switch matrix of N single-pole double-throw switches, a second switch matrix of two N-to-1 switches, a high-voltage excitation source, a voltage sampling unit, and a control unit.

[0007] One end of each current-limiting resistor is connected to a slip ring tap head, and the other end is connected in series with a sampling resistor and then to the fixed end of a single-pole double-throw switch in the first switch matrix;

[0008] The first moving terminals of all single-pole double-throw switches in the first switch matrix are short-circuited to a point and connected to the first output terminal of the high-voltage excitation source; the second moving terminals of all single-pole double-throw switches in the first switch matrix are short-circuited to another point and connected to the second output terminal of the high-voltage excitation source;

[0009] The N moving terminals of the first N-to-1 switch are respectively connected to one end of the sampling resistor, and the N moving terminals of the second N-to-1 switch are respectively connected to the other end of the sampling resistor; the stationary terminal of the first N-to-1 switch and the stationary terminal of the second N-to-1 switch are connected to the voltage sampling unit;

[0010] The control unit is respectively connected to the control terminal of the first switch matrix, the control terminal of the second switch matrix, and the control terminal of the voltage sampling unit through a digital control bus.

[0011] Preferably, the single-pole double-throw switch in the first switch matrix is an SPDT-type relay or an analog switch.

[0012] Preferably, the N-to-1 switch in the second switch matrix is a MUX-type analog switch or a combination of multiple relays.

[0013] Preferably, the high-voltage excitation source is a flyback transformer, and the reference potential of the high-voltage excitation source is connected to the reference potential of the sampling unit.

[0014] Preferably, the digital control bus includes isolators

[0015] The method involved in the present invention includes the following steps:

[0016] Step 1: Set the qualified threshold R of the insulation impedance between any two taps of the slip ring th .

[0017] Step 2: In the branch where all taps of the slip ring are connected in series with the sampling resistor, take an unmeasured sampling resistor tap as the independent tap, and short-circuit the sampling resistor taps of the remaining branches to a point.

[0018] Step 3: Measure the parallel insulation resistance between the independent tap and the short-circuit point, and check whether the measured insulation resistance value is greater than R th / (N - 1). If so, turn to Step 2; otherwise, continue to the next step.

[0019] Step 4: Measure the insulation resistance of each shunted branch, and the branch corresponding to the measurement result lower than R th is the faulty branch.

[0020] Step 5: If all branches have been tested as independent terminals, end; otherwise, jump back to Step 2.

[0021] Preferably, step 2 is specifically as follows: The control unit sends a control signal to drive the fixed end of the switch connected to the sampling resistor tap in the first switch matrix to conduct with the first moving end, and at the same time, the fixed ends of the remaining switches are conducted with the second moving end.

[0022] Preferably, in step 3, measuring the parallel insulation resistance between the independent tap and the short - connection point is specifically as follows: The control unit sends a control signal to drive the two N - to - 1 switches in the second switch matrix to select and conduct the moving ends of the switches connected to both ends of the sampling resistor corresponding to the independent tap; the voltage sampling unit samples the voltage across the sampling resistor, and the controller reads the sampling data and calculates the insulation resistance value according to the following formula:

[0023]

[0024] In the formula, Uo is the output voltage value of the high - voltage excitation source, Ups is the voltage across the sampling resistor, and Rps is the value of the sampling resistor.

[0025] Preferably, in step 4, measuring the insulation resistance of each shunted branch is specifically as follows: The control unit sends a control signal to drive the two N - to - 1 switches in the second switch matrix to select and conduct the moving ends of the switches connected to both ends of the sampling resistor of the branch to be measured; the voltage sampling unit samples the voltage across the sampling resistor, and the controller reads the sampling data and calculates the insulation resistance value according to the following formula:

[0026]

[0027] In the formula, Uo is the output voltage value of the voltage excitation source, Ubs is the voltage across the sampling resistor of the current branch, and Rbs is the value of the sampling resistor of the current branch.

[0028] Advantages of the present invention: First, the present invention preliminarily narrows the range of the defect location by testing the insulation resistance of each tap relative to the short - connection points of all other taps; then, the principle of the dichotomy method is used to quickly locate the defective tap combination. Accordingly, the present invention can effectively reduce the time required for testing a single conductive slip ring and improve the product detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the device for quickly measuring the insulation resistance of a conductive slip ring.

[0030] Figure 2 It is a flowchart of the method for quickly measuring the insulation resistance of a conductive slip ring. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To facilitate understanding of the solution and its effects of the embodiments of the present invention, a specific application example is given below. Those skilled in the art should understand that this example is only for facilitating the understanding of the present invention, and any specific details are not intended to limit the present invention in any way.

[0032] As Figure 1 shown, in this embodiment, the product line applied by the conductive slip ring insulation resistance rapid measurement device is a 6-tap conductive slip ring, the test voltage is 250V, and the insulation resistance between any two taps of the conductive slip ring shall not be less than 10MΩ.

[0033] In the device of this embodiment, the resistance ratio of the sampling resistor and the current-limiting resistor is determined by the test voltage and the input range of the voltage sampling unit. When the high-voltage excitation source is 250V and the input range of the voltage sampling unit is ±5V, the ratio of the sampling resistor to the current-limiting resistor shall not exceed 1:49, so as to ensure that the input signal of the voltage sampling unit does not exceed the range. At the same time, considering that the effective resolution of the input signal should be as high as possible, the values of the sampling resistor and the current-limiting resistor are determined to be 300Ω and 15kΩ respectively.

[0034] The first switch matrix includes 6 single-pole double-throw switches, and the switch type is a single-pole double-throw reed high-voltage relay with a withstand voltage of more than 300V. The second switch matrix includes two 6-to-1 high-voltage MUX analog switches with a withstand voltage of more than 300V.

[0035] One end of each current-limiting resistor is respectively connected to a slip ring tap. After the other end of the current-limiting resistor is connected in series with the sampling resistor, they are respectively connected to the stationary ends of the single-pole double-throw relays in the first switch matrix; the first moving ends of all the single-pole double-throw relays in the first switch matrix are short-circuited to one point and connected to the first output terminal of the high-voltage package; the second moving ends of all the single-pole double-throw relays in the first switch matrix are short-circuited to one point and connected to the second output terminal of the high-voltage package; the stationary ends of the two 6-to-1 analog switches in the second switch matrix are respectively connected to the two input terminals of the voltage sampling unit, and the 6 moving ends of one switch are respectively connected to one end of the sampling resistor, and the 6 moving ends of the other switch are respectively connected to the other end of the sampling resistor.

[0036] The voltage sampling unit is composed of an input protection circuit, a filter, and a 10-bit bipolar ADC. The reference ground of the voltage sampling unit is connected to the second output terminal (i.e., the power ground) of the high-voltage package, and its output signal is connected to the control unit through optical isolation by a 4N25 optocoupler via the SPI digital bus; the first switch matrix is driven by a ULN2803 Darlington transistor array chip, and the input signal of the chip is connected to the control unit through optical isolation by a 4N25 optocoupler; the control terminal of the second switch matrix is connected to the control unit through optical isolation by a 4N25 optocoupler. The isolation voltage at both ends of the 4N25 optocoupler is up to 5000V, thus effectively protecting the control unit from the risk of high-voltage impact.

[0037] As Figure 2 shown, when applying this device to test a certain conductive slip ring, the taps and their corresponding branches are numbered 1 to 6 according to the connection sequence, and the test process is as follows:

[0038] Step 1: Set the qualified threshold R of the insulation impedance between any two taps of the slip ring th to 10 MΩ.

[0039] Step 2: The control unit issues a control signal to drive the relay connecting to branch 1 in the first switch matrix to conduct to the first moving end, and at the same time, the relays connecting to other branches conduct to the second moving end, so as to take the tap of the sampling resistor corresponding to tap 1 as an independent tap, and short-circuit the taps of the sampling resistors of branches 2 to 5 to one point.

[0040] Step 3: The control unit issues a control signal to drive the two 6-to-1 switches in the second switch matrix to conduct the moving ends corresponding to the sampling resistor of branch 1, so as to connect the voltage sampling unit to the sampling resistor 1 and measure the parallel insulation resistance between tap 1 and the short-circuit point. Check whether the measured insulation resistance value is greater than R th / (N - 1) = 2 MΩ. If yes, it can be determined that there is no fault; otherwise, it is determined that there is a fault. If there is no fault and the measurement results of each branch are not required, directly go to Step 2; otherwise, continue to the next step.

[0041] Step 4: The control unit issues a control signal to drive the two 6-to-1 analog switches in the second switch matrix to sequentially switch to branches 2 to 6, and at the same time measure the insulation resistances of branches 2 to 6. The branch corresponding to the measurement result lower than 10 MΩ is the faulty branch.

[0042] Step 5: If all branches have been tested as independent ends, end; otherwise, jump back to Step 2.

[0043] In the whole measurement process of the present invention, only 6 high-voltage package boosting processes are required. After each pressurization, the measurement channel can be quickly switched, and 5 groups of insulation impedance values can be measured. The present invention reduces the required number of pressurizations by parallel pressurization, thereby improving the measurement efficiency of the insulation resistance of the conductive slip ring.

Claims

1. A rapid measurement method for the insulation resistance of a conductive slip ring. The device used includes sampling resistors and current-limiting resistors with the same number N as the number of slip ring taps, a first switch matrix of N single-pole double-throw switches, a second switch matrix of two 1-of-N switches, a high-voltage excitation source, a voltage sampling unit, and a control unit. It is characterized in that: One end of each current-limiting resistor is connected to a slip ring tap, and the other end is connected in series with the sampling resistor and then connected to the fixed end of a single-pole double-throw switch in the first switch matrix; The first moving ends of all the single-pole double-throw switches in the first switch matrix are short-circuited to one point and connected to the first output terminal of the high-voltage excitation source; the second moving ends of all the single-pole double-throw switches in the first switch matrix are short-circuited to another point and connected to the second output terminal of the high-voltage excitation source; The N moving ends of the first 1-of-N switch are respectively connected to one end of the sampling resistors, and the N moving ends of the second 1-of-N switch are respectively connected to the other end of the sampling resistors; the fixed end of the first 1-of-N switch and the fixed end of the second 1-of-N switch are connected to the voltage sampling unit; The control unit is respectively connected to the control terminals of the first switch matrix, the control terminals of the second switch matrix, and the control terminal of the voltage sampling unit through a digital control bus; It is characterized in that: the method includes the following steps: Step 1: Set the qualified threshold R of the insulation impedance between any two taps of the slip ring th ; Step 2: In the branches where all the slip ring taps are connected in series with the sampling resistors, take an unmeasured sampling resistor tap as an independent tap, and short-circuit the sampling resistor taps of the remaining branches to one point; Step 3: Measure the parallel insulation resistance between the independent tap and the short-circuit point, and check whether the measured insulation resistance value is greater than R th / (N - 1). If yes, go to Step 2; otherwise, continue to the next step; Step 4: Measure the insulation resistance of each shunted branch, and the branch corresponding to the measurement result lower than R th is the faulty branch; Step 5: If all the branches have been tested as independent ends, end; otherwise, jump back to Step 2.

2. A method for rapidly measuring the insulation resistance of a conductive slip ring according to claim 1, characterized in that, The single-pole double-throw switches in the first switch matrix are SPDT-type relays or analog switches.

3. A method for rapidly measuring the insulation resistance of a conductive slip ring according to claim 1, characterized in that, The 1-of-N switches in the second switch matrix are MUX-type analog switches or a combination of multiple relays.

4. A method for quickly measuring the insulation resistance of a conductive slip ring according to claim 1, characterized in that, The high-voltage excitation source is a high-voltage package, and the reference potential of the high-voltage excitation source is connected to the reference potential of the sampling unit.

5. A method for quickly measuring the insulation resistance of a conductive slip ring according to claim 1, characterized in that, The digital control bus includes isolators.

6. A rapid measurement method for the insulation resistance of a conductive slip ring according to claim 1, characterized in that: Step 2 is specifically: The control unit sends a control signal to drive the fixed end and the first moving end of the switch connected to the sampling resistor tap in the first switch matrix to conduct, and at the same time, the fixed end and the second moving end of the remaining switches are conducted.

7. A rapid measurement method for the insulation resistance of a conductive slip ring according to claim 1, characterized in that: In Step 3, measuring the parallel insulation resistance between the independent tap and the short-circuited point is specifically: The control unit sends a control signal to drive both 1-of-N switches in the second switch matrix to select the moving ends of the switches connected to both ends of the sampling resistor corresponding to the independent tap; the voltage sampling unit samples the voltage across the sampling resistor, and the controller reads the sampling data and calculates the insulation resistance value according to the following formula: In the formula, Uo is the output voltage value of the high-voltage excitation source, Ups is the voltage across the sampling resistor, and Rps is the value of the sampling resistor.

8. A rapid measurement method for the insulation resistance of a conductive slip ring according to claim 7, characterized in that: In step 4, the specific method for measuring the insulation resistance of each shunted branch is as follows: The control unit sends a control signal to drive the two 1-of-N switches in the second switch matrix to select the switch moving terminals connected to both ends of the sampling resistor of the branch to be measured; the voltage sampling unit samples the voltage across the sampling resistor, and the controller reads the sampling data and calculates the insulation resistance value according to the following formula: In the formula, Uo is the output voltage value of the voltage excitation source, Ubs is the voltage across the sampling resistor of the current branch, and Rbs is the sampling resistance value of the current branch.

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