CN116165438A - Motor insulation state monitoring circuit and monitoring method thereof - Google Patents

Motor insulation state monitoring circuit and monitoring method thereof Download PDF

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CN116165438A
CN116165438A CN202211688354.0A CN202211688354A CN116165438A CN 116165438 A CN116165438 A CN 116165438A CN 202211688354 A CN202211688354 A CN 202211688354A CN 116165438 A CN116165438 A CN 116165438A
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voltage
circuit
test
motor
insulation
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施其彪
范涛
温旭辉
钟子健
王哲涵
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Institute of Electrical Engineering of CAS
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Institute of Electrical Engineering of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/08—Measuring resistance by measuring both voltage and current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines

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Abstract

The invention provides a motor insulation state monitoring circuit and a monitoring method thereof, wherein the circuit comprises the following components: the voltage boosting circuit, the voltage sampling circuit, the control unit and the resistance switching circuit, wherein the resistance switching circuit comprises: a plurality of test branches, the test branches including: the test resistor and the controlled switch are connected in series, the orders of magnitude of the test resistors corresponding to different test branches are different, and the control end of the controlled switch corresponding to each test branch is connected with the control unit; and the third voltage sampling port of the control unit is respectively connected with each test resistor and is used for collecting the third voltage of the test resistor in the current access circuit. By utilizing the resistance switching circuit formed by a plurality of test branches of the resistance with different orders of magnitude, the size of the test resistance of the access circuit is controlled by the control unit, so that the accurate measurement of the insulation resistance is realized.

Description

Motor insulation state monitoring circuit and monitoring method thereof
Technical Field
The invention relates to the technical field of motor health management, in particular to a motor insulation state monitoring circuit and a motor insulation state monitoring method.
Background
Along with the popularization of the application of the new energy automobiles, the requirements on the technology of the new energy automobiles are also higher and higher. The driving motor technology is one of three core technologies of new energy automobiles, and is currently developing towards high power density, high torque control performance and high reliability, meanwhile, with the development of intelligent network automobiles, higher reliability and safety requirements are provided for the driving motor, and the application of the high-voltage quick-charging technology also provides challenges for design technologies such as insulation safety and the like of the driving motor. Aiming at the insulation safety problem of the motor, the traditional method mainly adopts off-line insulation resistance test and on-line insulation resistance monitoring.
However, the conventional off-line insulation resistance test method requires the use of a precise micro-current sensor, which is costly. In the traditional online insulation resistance monitoring method, the insulation resistance value is calculated through the bias resistance and the comparison voltage, the accuracy of a calculation result is related to the actual insulation resistance and the bias resistance, but when the actual insulation resistance value and the bias resistance value are larger in phase difference, the measurement accuracy is lower.
Disclosure of Invention
In view of the above, the embodiment of the invention provides a motor insulation state monitoring circuit and a motor insulation state monitoring method, so as to solve the problem that the monitoring precision and the cost of the motor insulation resistance monitoring method in the prior art are difficult to be compatible.
The embodiment of the invention provides a motor insulation state monitoring circuit, which comprises: the voltage boosting circuit, the voltage sampling circuit, the control unit and the resistance switching circuit, wherein,
the control end of the booster circuit is connected with the PWM output port of the control unit, and the output end of the booster circuit is connected with the positive electrode of the insulation test output of the motor to be tested and is used for applying preset test voltage to the motor to be tested;
the first input end of the voltage sampling circuit is connected with the insulation test output positive electrode of the motor to be tested, the second input end of the voltage sampling circuit is connected with the insulation test output negative electrode of the motor to be tested, and the first output end and the second output end of the voltage sampling circuit are respectively connected with the first voltage sampling port and the second voltage sampling port of the control unit and are used for respectively collecting the first voltage of the insulation test output positive electrode of the motor to be tested and the second voltage of the insulation test output negative electrode of the motor to be tested;
the resistance switching circuit includes: a plurality of test branches, the test branches comprising: the test resistor and the controlled switch are connected in series, the orders of magnitude of the test resistors corresponding to different test branches are different, and the control end of the controlled switch corresponding to each test branch is connected with the control unit;
the third voltage sampling port of the control unit is respectively connected with each test resistor and is used for collecting the third voltage of the test resistor in the current access circuit;
the control unit outputs PWM pulses to the booster circuit to control the test voltage generating circuit to output the preset test voltage to the motor to be tested, and controls the resistance switching circuit to switch different test resistances, so that the insulation resistance of the motor to be tested is calculated according to the first voltage, the second voltage and the third voltage.
Optionally, the motor insulation state monitoring circuit further includes:
and the first end of the switch circuit is connected with the insulation test output cathode of the motor to be tested, the second end of the switch circuit is connected with the resistance switching circuit, and the control end of the switch circuit is connected with the control unit.
Optionally, the boost circuit includes: a power supply, an inductance, a diode, a first controlled switch and a capacitance, wherein,
one end of the inductor is connected with the power supply, and the other end of the inductor is connected with the forward end of the diode and the first end of the first controlled switch respectively;
the control end of the first controlled switch is connected with the PWM output port of the control unit, and the second end of the first controlled switch is grounded;
and the reverse end of the diode is connected with the positive electrode of the insulation test output of the motor to be tested.
Optionally, the voltage sampling circuit includes: a first voltage sampling circuit and a second voltage sampling circuit, wherein,
the first voltage sampling circuit and the second voltage sampling circuit each include: a voltage dividing circuit;
the first end of the voltage dividing circuit of the first voltage sampling circuit is connected with the positive electrode of the insulation test output of the motor to be tested, the second end of the voltage dividing circuit is grounded, and the voltage dividing output end of the voltage dividing circuit is connected with the first voltage sampling port of the control unit;
and a first end of a voltage dividing circuit of the second voltage sampling circuit is connected with an insulation test output negative electrode of the motor to be tested, a second end of the voltage dividing circuit is grounded, and a voltage dividing output end of the voltage dividing circuit is connected with a second voltage sampling port of the control unit.
Optionally, the control unit is a microcontroller.
Optionally, the switching circuit includes: a second controlled switch.
Optionally, the number of the test branches is 4, and the resistance values of the test resistors corresponding to the test branches are respectively: 1mΩ, 100kΩ, 10kΩ, 1kΩ.
Optionally, the motor insulation state monitoring circuit further includes: and the communication interface unit is connected with the control unit and is used for realizing the communication between the control unit and external equipment.
The embodiment of the invention also provides a monitoring method of the motor insulation state monitoring circuit, which is applied to the control unit of the motor insulation state monitoring circuit, and comprises the following steps:
acquiring a preset test voltage of the motor to be tested;
generating corresponding PWM wave pulses based on the preset test voltage and outputting the PWM wave pulses to a control end of a boost circuit so that the boost circuit outputs the preset test voltage;
according to the sequence of the test resistor from small to large, controlling the corresponding controlled switch of the test resistor to be conducted, enabling the corresponding test resistor to be connected into a motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor;
judging whether the third voltage is in a preset input range;
and when the third voltage is in a preset input range, acquiring a first voltage and a second voltage acquired by a voltage sampling circuit, and calculating the insulation resistance of the motor to be tested according to the first voltage, the second voltage and the third voltage.
Optionally, when the third voltage is not in the preset input range, returning to the step of controlling the controlled switch corresponding to the test resistor to be turned on according to the sequence from small to large of the test resistor, so that the corresponding test resistor is connected to the motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor until the third voltage is in the preset input range.
The technical scheme of the invention has the following advantages:
1. according to the motor insulation state monitoring circuit provided by the embodiment of the invention, the insulation leakage current of the motor to be detected is converted into the voltage signal by utilizing the resistance switching circuit formed by the test branches of the resistors with different orders of magnitude, so that the insulation resistance is conveniently monitored, the size of the test resistor of the access circuit is controlled by the control unit, the insulation resistance is accurately measured in a low-cost mode, the insulation resistance is measured in a high-precision mode, the high-precision measurement is independent of an expensive precise voltage/current sensor, the universality and the availability are high, and the application and popularization of the technology are facilitated.
2. The monitoring method of the motor insulation state monitoring circuit provided by the embodiment of the invention is applied to the control unit of the motor insulation state monitoring circuit provided by the other embodiment of the invention, the insulation leakage current of the motor to be tested is converted into a voltage signal by utilizing the resistance switching circuit formed by a plurality of test branches of the resistors of different orders of magnitude, the insulation resistance is conveniently monitored by utilizing the test resistor, the size of the test resistor of the access circuit is controlled by the control unit, the accurate measurement of the insulation resistance is realized, the high-precision measurement of the insulation resistance is realized in a low-cost mode, the expensive precise voltage/current sensor is not relied on, the universality and the availability are strong, and the application and popularization of the technology are facilitated.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a conventional insulation tester in the prior art;
FIG. 2 is a schematic diagram of a bridge measurement method in the prior art;
fig. 3 is a schematic structural diagram of a motor insulation state monitoring circuit according to an embodiment of the present invention;
fig. 4 is a flowchart of a monitoring method of the motor insulation state monitoring circuit according to an embodiment of the invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The technical features of the different embodiments of the invention described below may be combined with one another as long as they do not conflict with one another.
The current traditional method mainly adopts off-line insulation resistance test and on-line insulation resistance monitoring. The off-line insulation resistance test principle is shown in fig. 1, and is generally implemented by using a 9V battery, the 9V battery voltage is raised to an insulation test voltage V of 500V, 1000V, etc. by a voltage-raising unit, and after the test voltage is applied to an insulator to be tested, the micro-current sensor detects that the test voltage flows through the insulator to be testedAnd the current I of the body, thereby obtaining the insulation resistance R=V/I of the tested insulator. The on-line insulation resistance monitoring principle is shown in figure 2, U DC Is the voltage of a direct current bus, E is the ground (car body), U P 、U N Respectively the voltage between the positive pole and the negative pole of the direct current bus and the ground, R 1 、R 2 S is a bias resistor for switching 1 、S 2 Is a switch. First, let S 1 And S is 2 Maintaining the disconnection state, and detecting the voltage U of the positive electrode and the negative electrode of the bus to the ground P And U N . If U is P ≥U N The insulation resistance value to the ground of the negative electrode of the direct current bus is smaller, and the switch S is closed at the moment 2 A bias resistor R is integrated between the negative electrode of the direct current bus and the ground 2 And detecting the voltage U of the positive electrode and the negative electrode of the direct current bus to the ground again P 'and U' N The insulation resistance values of the positive bus and the negative bus to the ground can be respectively obtained as follows:
Figure BDA0004019915980000061
if U is P ＜U N The insulation resistance value of the positive electrode of the direct current bus to the ground is smaller, and the switch S is closed at the moment 1 A bias resistor R is integrated between the positive electrode of the direct current bus and the ground 1 And detecting the voltage U of the positive electrode and the negative electrode of the direct current bus to the ground again P 'and U' N The insulation resistance values of the positive bus and the negative bus to the ground can be respectively obtained as follows:
Figure BDA0004019915980000062
however, the conventional off-line insulation resistance test method requires the use of a precise micro-current sensor, which is costly. In the traditional online insulation resistance monitoring method, the insulation resistance value is calculated through the bias resistance and the comparison voltage, the accuracy of a calculation result is related to the actual insulation resistance and the bias resistance, but when the actual insulation resistance value and the bias resistance value are larger in phase difference, the measurement accuracy is lower. Meanwhile, the conventional insulation detection or monitoring method is difficult to measure high-frequency insulation leakage current, the measurement bandwidth is usually smaller than 1kHz, and sufficient data is difficult to provide for the feature extraction of the insulation health state.
Based on the above-mentioned problems, an embodiment of the present invention provides a motor insulation state monitoring circuit, as shown in fig. 3, including: a boost circuit 101, a voltage sampling circuit, a control unit 105, and a resistance switching circuit 104, wherein,
the control end of the booster circuit 101 is connected with a PWM output port of the control unit 105, and the output end is connected with an insulation test output positive electrode P of the motor to be tested and is used for applying a preset test voltage to the motor to be tested; the first input end of the voltage sampling circuit is connected with the insulation test output positive electrode P of the motor to be tested, the second input end of the voltage sampling circuit is connected with the insulation test output negative electrode N of the motor to be tested, the first output end and the second output end of the voltage sampling circuit are respectively connected with the first voltage sampling port and the second voltage sampling port of the control unit 105, and the voltage sampling circuit is used for respectively collecting the first voltage U of the insulation test output positive electrode P of the motor to be tested P And a second voltage U of the insulation test output cathode N N The method comprises the steps of carrying out a first treatment on the surface of the The resistance switching circuit 104 includes: 4 test branches, the test branch includes: the test resistor and the controlled switch are connected in series, the orders of magnitude of the test resistors corresponding to different test branches are different, and the control end of the controlled switch corresponding to each test branch is connected with the control unit 105; a third voltage sampling port of the control unit 105 is respectively connected with each test resistor and is used for collecting the third voltage of the test resistor in the current access circuit; the control unit 105 controls the test voltage generating circuit to output a preset test voltage to the motor to be tested by outputting a PWM pulse to the booster circuit 101, and switches different test resistors by controlling the resistance switching circuit 104 according to the first voltage U P Second voltage U N And calculating the insulation resistance of the motor to be tested by the third voltage.
Specifically, the number of the test branches is 4, and the resistance values of the test resistors corresponding to the test branches are respectively: 1mΩ, 100kΩ, 10kΩ, 1kΩ. It should be noted that in the embodiment of the present invention, the description is made by taking 4 test branches as an example, and in practical application, the number of test branches and the specific value of the test resistor may be flexibly set according to the actual needs, which is not limited to this.
Illustratively, as shown in fig. 3, the resistance switching circuit 104 includes four series circuits of MOSFETs and resistors, wherein the gates of the MOSFETs are connected to the GPIO module of the control unit 105, and the resistances of the series resistors R5, R6, R7, and R8 differ by an order of magnitude, such as 1mΩ, 100kΩ, 10kΩ, and 1kΩ, respectively. The series resistor is used for converting the insulated leakage current into a voltage signal, and one end of the series resistor connected with the MOSFET is connected to the AD module of the control unit 105.
Through the cooperation of the components, the insulation state monitoring circuit for the motor provided by the embodiment of the invention converts insulation leakage current of the motor to be tested into voltage signals by using the resistance switching circuit formed by a plurality of test branches with different orders of magnitude of resistance, is convenient for monitoring the insulation resistance, and controls the size of the test resistance of the access circuit by the control unit, so that the accurate measurement of the insulation resistance is realized.
The control unit 105 is illustratively a microcontroller. Alternative models include TMS320F280021, etc., with the chip of the microcontroller having PWM modules, AD modules, GPIO modules, CAN communication modules, etc. In practical applications, the control unit 105 may also use other chips with data processing functions, such as a single chip microcomputer, and the invention is not limited thereto.
Specifically, in one embodiment, as shown in fig. 3, the motor insulation state monitoring circuit further includes: and a first end of the switch circuit 103 is connected with an insulation test output cathode N of the motor to be tested, a second end of the switch circuit 103 is connected with the resistance switching circuit 104, and a control end of the switch circuit 103 is connected with the control unit 105. Further, the switching circuit 103 includes: a second controlled switch Q2. The second controlled switch Q2 may be a high voltage MOSFET, for example, a 1200V withstand voltage MOSFET with a withstand voltage not lower than an insulation test voltage, for example, 1000V, and a gate of the MOSFET is connected to the GPIO module of the control unit 105. In practical applications, the second controlled switch Q2 may also use other switching devices such as a triode, which is not limited by the present invention. Through switching on the switch circuit 103 again after the switching of the test resistor is accomplished to the resistance switching circuit 104, realized the safe switching of test resistor, avoid the circuit potential safety hazard that electrified switching caused, and then promote the security of motor insulation state monitoring circuit.
Specifically, in one embodiment, as shown in fig. 3, the booster circuit 101 includes: the power supply VCC, an inductor L1, a diode D1, a first controlled switch Q1 and a capacitor C5, wherein one end of the inductor L1 is connected with the power supply, and the other end of the inductor L1 is respectively connected with the forward end of the diode D1 and the first end of the first controlled switch Q1; the control end of the first controlled switch Q1 is connected with the PWM output port of the control unit 105, and the second end is grounded; the reverse end of the diode D1 is connected with an insulation test output positive electrode P of the motor to be tested.
For example, the first controlled switch Q1 may be a high-voltage MOSFET, the MOSFET is connected to the PWM module of the control unit 105, the cathode of the diode D1 is connected to the positive electrode P of the insulation test output, and the control unit 105 outputs a PWM pulse voltage to drive the high-voltage MOSFET to perform a switching operation, so as to boost the voltage of the low-voltage power supply to a high voltage set by a user, such as 1000V.
Specifically, in one embodiment, the voltage sampling circuit includes: a first voltage sampling circuit 107 and a second voltage sampling circuit 102, wherein the first voltage sampling circuit 107 and the second voltage sampling circuit 102 each include: a voltage dividing circuit; the first end of the voltage dividing circuit of the first voltage sampling circuit 107 is connected with the insulation test output positive electrode P of the motor to be tested, the second end of the voltage dividing circuit is grounded, and the voltage dividing output end of the voltage dividing circuit is connected with the first voltage sampling port of the control unit 105; the first end of the voltage dividing circuit of the second voltage sampling circuit 102 is connected with the insulation test output cathode N of the motor to be tested, the second end is grounded, and the voltage dividing output end is connected with the second voltage sampling port of the control unit 105.
Illustratively, as shown in FIG. 3, the first voltage sampling circuit 107 includes resistors R1 and R2, and capacitors C1 and C2Their values satisfy r1=c1=r2×c2. One end of the first voltage sampling circuit 107 is connected to the positive electrode P of the insulation test output, the other end is connected to the power ground GND, and the midpoints of the voltage dividing resistors R1 and R2 are connected to the AD module of the control unit 105, so that the insulation test high-voltage dc power supply voltage is collected by the resistive-capacitive voltage dividing principle and used as a feedback signal for controlling the boost circuit 101 (i.e. the first voltage U P ). The second voltage sampling circuit 102 includes resistors R3 and R4 and capacitors C3 and C4, and their values satisfy r3=r4=r4×c4. One end of the second voltage sampling circuit 102 is connected to the insulation test output negative electrode N, the other end is connected to the power ground GND, and the midpoints of the voltage dividing resistors R3 and R4 are connected to the analog-to-digital converter of the control unit 105, so as to collect the actual loading voltage of the tested insulator (namely the second voltage U according to the resistance-capacitance voltage dividing principle) N )。
Specifically, in one embodiment, as shown in fig. 3, the motor insulation state monitoring circuit further includes: and a communication interface unit 106, where the communication interface unit 106 is connected to the control unit 105, and is used to implement communication between the control unit 105 and an external device.
Illustratively, the communication interface unit 106 includes a communication interface chip, and optional models include ISO1050, etc. for CAN bus transceiving. One end of the communication interface unit 106 is connected to the CAN communication module of the control unit 105.
The operation of the motor insulation state monitoring circuit shown in fig. 3 according to the embodiment of the present invention will be described in detail with reference to specific application examples.
First, the user sends insulation test instructions and related test parameters such as test voltage to the control unit 105 through the communication interface unit 106, and the control unit 105 controls the boost circuit 101 to output a specified insulation test voltage, such as 1000V, through the AD module and the PWM module. Then, the control unit 105 sequentially controls Q6, Q5, Q4, Q3 of the resistance switching circuit 104 to be turned on through the GPIO module. Then Q2 of the switch circuit 103 is conducted, voltage on the test resistor corresponding to the MOSFET in the resistance switching circuit 104 is collected, and the insulation resistance range of the tested motor is judged according to the voltage, so that the MOSFET in the corresponding resistance switching circuit 104 is switchedThe best test resistor is matched to improve the insulation resistance measurement accuracy. For example, for a measured insulation resistance of 100mΩ, 1000V insulation test voltage is used, and the resistances of R5, R6, R7, and R8 are 1mΩ, 100kΩ, 10kΩ, and 1kΩ in this order. When the output voltage of the booster circuit 101 reaches 1000V, Q5 is turned on first, and the voltage U on R8 is collected R8 U is then R8 About 10mV, the insulation resistance of the insulator to be tested is calculated to be about 100MΩ by the control unit 105, and then the voltage U on R6 is acquired after the switch to Q4 conduction R6 U is then R6 Approximately 1V, the over-control unit 105 calculates the insulation resistance R of the insulator to be tested test Is that
Figure BDA0004019915980000101
Since the input range of the AD module of the microcontroller is usually 2.5V-3.3V, U is adopted R6 The calculated insulation resistance value is far higher than that obtained by adopting U R8 The calculated insulation resistance value is more accurate. According to this principle, extremely high insulation resistance measurement accuracy can be realized by switching appropriate series resistances.
The motor insulation state monitoring circuit provided by the invention can record and carry out high-speed AD sampling while measuring insulation resistance, thereby acquiring detailed dielectric characteristic data and the like of a tested motor.
The embodiment of the invention provides a method for accurately measuring the insulation resistance by using a resistance switching mode on the basis of analyzing the advantages and disadvantages of the insulation state monitoring technology in the prior art, can realize high-precision measurement of the insulation resistance in a low-cost mode, can achieve more than 1MHz in measurement bandwidth of insulation voltage and insulation leakage current, does not depend on an expensive precise voltage/current sensor, has strong universality and availability, and is more beneficial to application and popularization of the technology.
The embodiment of the invention also provides a monitoring method of the motor insulation state monitoring circuit, which is applied to the control unit shown in fig. 3, and as shown in fig. 4, the monitoring method of the motor insulation state monitoring circuit comprises the following steps:
step S101: and acquiring a preset test voltage of the motor to be tested.
The preset test voltage can be extracted from test parameters sent to the control unit by a user.
Step S102: and generating corresponding PWM wave pulses based on the preset test voltage and outputting the PWM wave pulses to a control end of the booster circuit so that the booster circuit outputs the preset test voltage.
Specifically, the on frequency of the first controlled switch in the boost circuit can be controlled by adjusting the duty ratio of the PWM wave pulse, so as to control the output voltage of the boost circuit, and the duty ratio of the PWM wave pulse is calculated as the prior art, which is not described herein.
Step S103: and controlling the conduction of the controlled switch corresponding to the test resistor according to the sequence from small to large of the test resistor, enabling the corresponding test resistor to be connected into the motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor.
Specifically, when the insulation resistance range of the motor is not determined, the test is performed according to the sequence from small to large of the test resistance, so that the risk of damage to the test unit caused by overlarge access to the test resistance and exceeding the range of the control unit can be avoided, the safety of the insulation state monitoring circuit of the motor is improved, and the service life is prolonged.
Step S104: and judging whether the third voltage is in a preset input range.
Step S105: when the third voltage is in a preset input range, the first voltage and the second voltage acquired by the voltage sampling circuit are acquired, and the insulation resistance of the motor to be tested is calculated according to the first voltage, the second voltage and the third voltage.
The preset input range is exemplified by 2.5V to 3.3V, and in practical application, the preset input range and parameters of the AD module of the control unit are determined, which is only exemplified and not limited thereto.
Step S106: and when the third voltage is not in the preset input range, returning to the step of controlling the controlled switch corresponding to the test resistor to be conducted according to the sequence from small to large of the test resistor, enabling the corresponding test resistor to be connected into the motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor until the third voltage is in the preset input range.
The more accurate the measured value in the preset input range, the higher the accuracy of the insulation resistance can be improved by controlling the voltage of the test resistor in the preset input range of the control unit.
By executing the steps, the monitoring method of the motor insulation state monitoring circuit provided by the embodiment of the invention converts insulation leakage current of a motor to be tested into voltage signals by using the resistance switching circuit formed by a plurality of test branches of the resistors of different orders of magnitude, is convenient for monitoring the insulation resistance, realizes accurate measurement of the insulation resistance by controlling the size of the test resistor connected into the circuit by the control unit, realizes high-precision measurement of the insulation resistance in a low-cost manner, does not depend on an expensive precise voltage/current sensor, has strong universality and availability, and is more beneficial to application and popularization of technology.
Although embodiments of the present invention have been described in connection with the accompanying drawings, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, and such modifications and variations are within the scope of the invention as defined by the appended claims.

Claims (10)

1. A motor insulation state monitoring circuit, comprising: the voltage boosting circuit, the voltage sampling circuit, the control unit and the resistance switching circuit, wherein,
the control end of the booster circuit is connected with the PWM output port of the control unit, and the output end of the booster circuit is connected with the positive electrode of the insulation test output of the motor to be tested and is used for applying preset test voltage to the motor to be tested;
the first input end of the voltage sampling circuit is connected with the insulation test output positive electrode of the motor to be tested, the second input end of the voltage sampling circuit is connected with the insulation test output negative electrode of the motor to be tested, and the first output end and the second output end of the voltage sampling circuit are respectively connected with the first voltage sampling port and the second voltage sampling port of the control unit and are used for respectively collecting the first voltage of the insulation test output positive electrode of the motor to be tested and the second voltage of the insulation test output negative electrode of the motor to be tested;
the resistance switching circuit includes: a plurality of test branches, the test branches comprising: the test resistor and the controlled switch are connected in series, the orders of magnitude of the test resistors corresponding to different test branches are different, and the control end of the controlled switch corresponding to each test branch is connected with the control unit;
the third voltage sampling port of the control unit is respectively connected with each test resistor and is used for collecting the third voltage of the test resistor in the current access circuit;
the control unit outputs PWM pulses to the booster circuit to control the test voltage generating circuit to output the preset test voltage to the motor to be tested, and controls the resistance switching circuit to switch different test resistances, so that the insulation resistance of the motor to be tested is calculated according to the first voltage, the second voltage and the third voltage.
2. The motor insulation state monitoring circuit according to claim 1, further comprising:
and the first end of the switch circuit is connected with the insulation test output cathode of the motor to be tested, the second end of the switch circuit is connected with the resistance switching circuit, and the control end of the switch circuit is connected with the control unit.
3. The motor insulation state monitoring circuit according to claim 1, wherein the step-up circuit includes: a power supply, an inductance, a diode, a first controlled switch and a capacitance, wherein,
one end of the inductor is connected with the power supply, and the other end of the inductor is connected with the forward end of the diode and the first end of the first controlled switch respectively;
the control end of the first controlled switch is connected with the PWM output port of the control unit, and the second end of the first controlled switch is grounded;
and the reverse end of the diode is connected with the positive electrode of the insulation test output of the motor to be tested.
4. The motor insulation state monitoring circuit according to claim 1, wherein the voltage sampling circuit includes: a first voltage sampling circuit and a second voltage sampling circuit, wherein,
the first voltage sampling circuit and the second voltage sampling circuit each include: a voltage dividing circuit;
the first end of the voltage dividing circuit of the first voltage sampling circuit is connected with the positive electrode of the insulation test output of the motor to be tested, the second end of the voltage dividing circuit is grounded, and the voltage dividing output end of the voltage dividing circuit is connected with the first voltage sampling port of the control unit;
and a first end of a voltage dividing circuit of the second voltage sampling circuit is connected with an insulation test output negative electrode of the motor to be tested, a second end of the voltage dividing circuit is grounded, and a voltage dividing output end of the voltage dividing circuit is connected with a second voltage sampling port of the control unit.
5. The motor insulation state monitoring circuit of claim 1, wherein the control unit is a microcontroller.
6. The motor insulation state monitoring circuit according to claim 2, wherein the switching circuit includes: a second controlled switch.
7. The motor insulation state monitoring circuit according to claim 1, wherein the number of the test branches is 4, and the resistance values of the test resistors corresponding to the test branches are respectively: 1mΩ, 100kΩ, 10kΩ, 1kΩ.
8. The motor insulation state monitoring circuit according to any one of claims 1 to 7, further comprising: and the communication interface unit is connected with the control unit and is used for realizing the communication between the control unit and external equipment.
9. A monitoring method of an insulation state monitoring circuit of an electric motor, applied to a control unit of an insulation state monitoring circuit of an electric motor according to any one of claims 1 to 8, the method comprising:
acquiring a preset test voltage of the motor to be tested;
generating corresponding PWM wave pulses based on the preset test voltage and outputting the PWM wave pulses to a control end of a boost circuit so that the boost circuit outputs the preset test voltage;
according to the sequence of the test resistor from small to large, controlling the corresponding controlled switch of the test resistor to be conducted, enabling the corresponding test resistor to be connected into a motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor;
judging whether the third voltage is in a preset input range;
and when the third voltage is in a preset input range, acquiring a first voltage and a second voltage acquired by a voltage sampling circuit, and calculating the insulation resistance of the motor to be tested according to the first voltage, the second voltage and the third voltage.
10. The method for monitoring the insulation state of a motor according to claim 9, wherein,
and when the third voltage is not in the preset input range, returning to the step of controlling the controlled switch corresponding to the test resistor to be conducted according to the sequence from small to large of the test resistor, enabling the corresponding test resistor to be connected into the motor insulation state monitoring circuit, and collecting the third voltage of the current test resistor until the third voltage is in the preset input range.
CN202211688354.0A 2022-12-27 2022-12-27 Motor insulation state monitoring circuit and monitoring method thereof Pending CN116165438A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211688354.0A CN116165438A (en) 2022-12-27 2022-12-27 Motor insulation state monitoring circuit and monitoring method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211688354.0A CN116165438A (en) 2022-12-27 2022-12-27 Motor insulation state monitoring circuit and monitoring method thereof

Publications (1)

Publication Number Publication Date
CN116165438A true CN116165438A (en) 2023-05-26

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211688354.0A Pending CN116165438A (en) 2022-12-27 2022-12-27 Motor insulation state monitoring circuit and monitoring method thereof

Country Status (1)

Country Link
CN (1) CN116165438A (en)

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