Motor insulation leakage current segmentation variable gain amplification circuit and measurement method

Abstract

The invention discloses a motor insulation leakage current segmentation variable gain amplification circuit and a measurement method, and the method comprises the steps: converting a sine AC leakage current with a wide detection range into a sine AC voltage signal through a zero-flux leakage current sensor, and converting the sine AC voltage signal into a DC voltage signal through an AC signal amplifier and a full-wave rectification sine effective value circuit; a leakage current analog signal in a normal working range of a digital / analog converter (ADC) module of a digital signal processor (DSP) and a marking signal for marking an interval in which the magnitude of the leakage current is positioned are obtained through an online segmented variable gain amplification circuit consisting of an integrated operational amplifier, an integrated voltage comparator, a relay and the like; therefore, accurate restoration of the effective value of the original wide-range leakage current can be realized in a DSP (Digital Signal Processor) program through the marking signal of the interval where the leakage current is located and the sampling value of the leakage current.

Description

Technical Field

[0001] The invention belongs to the technical field of AC motor stator insulation fault diagnosis and online monitoring, and more specifically, relates to a motor insulation leakage current segmented variable gain amplifier circuit and a measurement method. Background Art

[0002] Stator insulation failure is one of the common fault types of AC motors. Although the offline detection method is a widely used method for evaluating the insulation performance of motors, it has limitations such as shutdown detection and long detection cycle. With the advancement of technology, a variety of online monitoring methods for AC motor stator insulation failures based on offline test principles have emerged. They overcome the limitations of offline detection and can perform real-time monitoring and online evaluation of the stator insulation status of running motors. They have become one of the key technologies to improve the safe and stable operation level of motors.

[0003] In the online monitoring technology of AC motor stator insulation, the monitoring method based on leakage current and impedance spectrum can effectively reflect the advantages of insulation aging and is one of the research hotspots of online monitoring technology of AC motor stator insulation.

[0004] During the aging process of AC motor stator insulation, the insulation resistance to ground gradually decreases, the insulation capacitance gradually increases, and the time-frequency domain characteristics of its leakage current also change accordingly. Because the leakage current is strongly related to the insulation impedance, a high-precision AC leakage current detection circuit is an essential part of the digital high-performance AC motor insulation online detection equipment.

[0005] However, the degradation of AC motor stator insulation is generally a long-term development process. During the slow and continuous degradation of stator insulation, the insulation impedance of AC motor stator to ground changes slowly and continuously, and its insulation leakage current also changes slowly and continuously. It can be seen that in the long-term online monitoring of AC motor stator insulation, due to the wide range of stator insulation leakage current variation, if a fixed gain amplifier is used to amplify and condition the insulation leakage current, there are the following problems: on the one hand, when the overall degradation of its stator insulation is serious, for a large leakage current signal, not only is the output of the amplifier easy to saturate, but the analog signal input to the digital signal processor (DSP) analog / digital converter (ADC) module is easy to exceed the allowable range; on the other hand, in the early stage of its stator insulation degradation, for a small leakage current signal, noise interference will affect the conversion accuracy of the leakage current signal.

[0006] Existing conventional variable gain amplifiers have the limitations of complex structure and control method, limited gain variation range and dynamic performance, and difficulty in accurately restoring the original input signal.

[0007] Therefore, in response to the need for long-term online monitoring of AC motor stator insulation, a variable gain amplifier for wide-range leakage current measurement signals is developed. The gain of the amplifier is automatically adjusted online according to the size of the measured AC leakage current signal to ensure that both large leakage current signals and small leakage current signals can be reasonably amplified with high precision to the allowable range of the analog signal of the DSP ADC module. At the same time, the original wide-range AC leakage current signal must be accurately restored in the DSP program, which is of great significance for the development of high-performance digital AC motor insulation online detection equipment. Summary of the invention

[0008] In order to solve the deficiencies in the prior art, the present invention provides an online segmented variable gain amplifier circuit and a measurement method for a wide range of AC leakage current measurement signal, so as to realize high-precision measurement of a wide range of AC leakage current required for long-term online monitoring of stator insulation of AC motors.

[0009] The present invention adopts the following technical solution.

[0010] The first aspect of the present invention provides a motor insulation leakage current segmented variable gain amplifier circuit comprising: a signal acquisition and conversion module, a series voltage division module, an integrated voltage comparison module, a DC relay control module, an integrated operational amplifier module and a level conversion circuit;

[0011] The signal acquisition and conversion module includes: a zero-flux leakage current sensor, an AC small signal amplifier, and a full-wave rectified sinusoidal effective value circuit. The signal acquisition and conversion module is used to acquire and convert the AC motor leakage current into a DC voltage signal corresponding to the effective value of the leakage current;

[0012] The series voltage divider module includes n series-connected resistors, and the series voltage divider module is used to use the divided voltage of each resistor as the reference voltage value of the boundary of n leakage current intervals;

[0013] The integrated voltage comparison module includes n integrated voltage comparators, and the integrated voltage comparison module is used to segment the DC voltage signal according to the comparison result between the DC voltage signal and the reference voltage values ​​at the boundaries of the n intervals, so as to obtain the interval marking signal of the leakage current;

[0014] The DC relay control module includes n DC relays and corresponding n transistors for controlling whether the DC relays work or not. The DC relay control module is used to control the integrated operational amplifier module to select a feedback branch according to the interval marking signal to obtain different gains.

[0015] The integrated operational amplifier module includes an integrated operational amplifier and n parallel feedback branches, the n feedback branches correspond to n different gains, and the integrated operational amplifier module is used to amplify the DC voltage signal to generate a leakage current sampling value within the normal working range of the analog / digital converter and output it;

[0016] The level conversion circuit is used to convert the interval mark signal into an input signal within the normal working range of the general input / output multiplexer.

[0017] Preferably, the series voltage divider module is composed of n resistors, namely a first resistor, a second resistor, ..., and an nth resistor connected in series. One end of the first resistor of the series voltage divider module is connected to the positive end of the first DC power supply, and the other end is connected to one end of the second resistor. One end of the nth resistor is connected to one end of the n-1th resistor, and the other end is grounded.

[0018] Preferably, the integrated voltage comparison module is composed of n integrated voltage comparators, the inverting input terminals of the first integrated voltage comparator, the second integrated voltage comparator, ..., and the n-1th integrated voltage comparator are respectively connected between the first resistor and the second resistor, between the second resistor and the third resistor, ..., between the n-1th resistor and the nth resistor, the inverting input terminal of the nth integrated voltage comparator n is grounded, and the DC voltage signal output by the signal acquisition and conversion module is input to the non-inverting input terminals of the n integrated voltage comparators via resistors.

[0019] Preferably, in the DC relay control module, the transistor is an NPN transistor, the DC relay includes a coil, a normally open contact and a normally closed contact, the DC relay control module receives the interval marking signal through the NPN transistor and drives the corresponding DC relay, and the DC relay controls the integrated operational amplifier module to select the feedback branch by closing the normally open contact.

[0020] Preferably, the base of each NPN transistor is connected to the output terminal of the integrated voltage comparator through a resistor;

[0021] The collector of each NPN transistor is connected to one end of the corresponding DC relay coil, the normally closed contacts of the first n-1 DC relays are connected in series in sequence, the other end of the first DC relay coil is connected to the other end of its normally closed contact and connected to the positive end of the second DC power supply, the other ends of the second DC relay, ..., the n-1th DC relay coils are respectively connected between the normally closed contact of the DC relay and the normally closed contact of the previous DC relay, and the other end of the nth DC relay coil is connected to the other end of the normally closed contact of the n-1th DC relay;

[0022] The emitter of each NPN transistor is connected to ground through a resistor.

[0023] Preferably, each DC relay coil is connected with a diode in anti-parallel.

[0024] Preferably, in the integrated operational amplifier module, the feedback branch is composed of a feedback resistor and a normally open contact of a DC relay connected in series; the DC voltage signal output by the signal acquisition and conversion module is input to the non-inverting input terminal of the integrated operational amplifier through a non-inverting resistor, the inverting input terminal of the integrated operational amplifier is grounded through an inverting resistor, the output terminal of the integrated operational amplifier is connected to the inverting input terminal of the integrated operational amplifier through a feedback branch, and the output terminal of the integrated operational amplifier is connected to the ADC module of the DSP.

[0025] Preferably, a diode connected end to end is added to the output end of the integrated operational amplifier, wherein the cathode of the diode whose anode is connected to the output end of the integrated operational amplifier is connected to the positive end of the third DC power supply, and the anode of the diode whose cathode is connected to the output end of the integrated operational amplifier is grounded.

[0026] A second aspect of the present invention provides a method for measuring motor insulation leakage current, which uses the motor insulation leakage current segmented variable gain amplifier circuit to measure the motor insulation leakage current, and includes the following steps:

[0027] Step 1, collecting the original AC motor leakage current and converting it into a DC voltage signal corresponding to the effective value of the leakage current;

[0028] Step 2: Set the reference voltage value of the boundary of the leakage current n intervals, and obtain the interval marking signal a according to the segmented interval i of the DC voltage signal obtained in step 1. 1 , a 2 , …, a i , …, a n , where a 1 , …, a i-1 =0,a i , …, a n =1, and amplify the corresponding multiple to obtain the leakage current sampling value;

[0029] Step 3, calculating the effective value of the original AC motor leakage current according to the interval marking signal and the leakage current sampling value obtained in step 2.

[0030] Preferably, in step 2, the sizes of the first resistor, the second resistor, ..., and the nth resistor are selected, and a voltage divider circuit consisting of n resistors connected in series is used to obtain reference voltage values ​​of n interval boundaries of the leakage current, wherein the reference voltage value of the interval boundary of the segmented interval i is expressed by the following formula:

[0031]

[0032] V i上 =V i-1下

[0033] Where:

[0034] V i下 Represents the lower limit of the reference voltage value of segment interval i;

[0035] V i上 Represents the upper limit of the reference voltage value of segment interval i;

[0036] |V c1 | is the voltage value of the first DC power supply.

[0037] Preferably, step 3 specifically includes:

[0038] Read the leakage current sampling value and the interval marking signal;

[0039] According to the interval marking signal, the feedback resistor connected to the integrated operational amplifier feedback branch is determined, and then the corresponding amplification factor is obtained. The feedback resistor R F1 , R F2 , …, R Fn And the op amp gain K 1 , K 2 , …, K n The corresponding relationship is expressed by the following formula:

[0040] K j =(1+R Fj / |R m |)

[0041] Where:

[0042] R Fj represents the feedback resistance value of the jth feedback branch;

[0043] |R m | represents the resistance value connected to the ground of the inverting input terminal of the integrated operational amplifier;

[0044] According to the zero-flux leakage current sensor, AC small signal amplifier, and full-wave rectified sinusoidal effective value circuit parameters, the effective value of the original AC motor leakage current is calculated by combining the leakage current sampling value and the amplification factor.

[0045] Preferably, according to the relationship between the analog voltage input to the ADC module of the DSP and the leakage current sampling value, the integrated operational amplifier output signal V is obtained from the leakage current sampling value. F , calculate the effective value of the original AC motor leakage current according to the following formula:

[0046]

[0047] Where:

[0048] I LC Indicates the effective value of the original AC motor leakage current;

[0049] V F Represents the integrated operational amplifier output signal;

[0050] GLC Indicates the conversion coefficient between the input current and output voltage of the zero flux leakage current sensor;

[0051] G AC Indicates the amplification factor of the AC small signal amplifier;

[0052] G rms Indicates the transformation coefficient of the full-wave rectified sine effective value circuit, G rms =1.

[0053] Compared with the prior art, the beneficial effects of the present invention include at least: compared with the conventional variable gain amplifier, the technical solution proposed by the present invention and its specific circuit have the advantages of simple structure, low cost, large gain variation range, and accurate restoration of the original wide range AC leakage current effective value, etc., which is suitable for the long-term online monitoring of AC motor stator insulation based on leakage current detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of a motor insulation leakage current segmented variable gain amplifier circuit provided in accordance with an embodiment of the present invention;

[0055] Figure 2 It is a subroutine flowchart of DSP leakage current restoration provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0057] The invention adopts a zero-flux leakage current sensor to convert the sinusoidal AC leakage current of an AC motor with a wide detection range into a sinusoidal AC voltage signal, which is then converted into a DC voltage signal by an AC signal amplifier and a full-wave rectified sinusoidal effective value circuit, and then is converted into a DC voltage signal by an online segmented variable gain amplifier circuit composed of an integrated operational amplifier, an integrated voltage comparator and a relay, so as to obtain a leakage current analog signal within the normal working range of a digital signal processor (DSP) analog / digital converter (ADC) module and a marking signal marking the interval where the leakage current is located, so that the original wide-range leakage current effective value can be accurately restored in a DSP program through the marking signal of the interval where the leakage current is located and the leakage current sampling value.

[0058] like Figure 1As shown, embodiment 1 of the present invention provides a motor insulation leakage current segmented variable gain amplifier circuit, including: a signal acquisition and conversion module, a series voltage division module, an integrated voltage comparison module, a DC relay control module, an integrated operational amplifier module and a level conversion circuit.

[0059] The signal acquisition and conversion module specifically includes: a zero-flux leakage current sensor, an AC small signal amplifier and a full-wave rectified sinusoidal effective value circuit connected in sequence, which is used to collect the AC motor leakage current and convert it into a DC voltage signal corresponding to the leakage current effective value.

[0060] The series voltage divider module consists of n resistors. The first resistor R 1 , the second resistor R 2 , ..., nth resistor R n The first resistor R of the series voltage divider module 1 One end is connected to the first DC power supply V c1 The positive end of the resistor R 2 One end of the nth resistor R n One end is connected to the n-1th resistor R n-1 One end of the resistor is connected to the ground, and the other end is grounded, so as to use the divided voltage of each resistor as the reference voltage value of the boundary of n leakage current intervals.

[0061] The integrated voltage comparison module is composed of n integrated voltage comparators, and the inverting input terminals of the first integrated voltage comparator 1, the second integrated voltage comparator 2, ..., and the n-1th integrated voltage comparator n-1 are respectively connected to the first resistor R 1 and the second resistor R 2 Between, the second resistor R 2 and the third resistor R 3 Between, ..., the n-1th resistor R n-1 and the nth resistor R n The inverting input terminal of the nth integrated voltage comparator n is grounded, and the DC voltage signal output by the signal acquisition and conversion module is connected to the ground through the resistor R 0 The DC voltage signal is input to the non-inverting input terminal of n integrated voltage comparators, and is used to segment the DC voltage signal according to the comparison result between the DC voltage signal and the reference voltage values ​​at the boundaries of the n intervals, so as to obtain the interval marking signal of the leakage current.

[0062] The DC relay control module includes n DC relays and n NPN transistors for controlling whether the DC relays work or not. The DC relays include a coil, a normally open contact and a normally closed contact. The base of each NPN transistor is connected to the DC relay by a resistor R B1 , …, R BnThe output terminal of the integrated voltage comparator is connected to the collector of each transistor, and the collector of each transistor is connected to one end of the corresponding DC relay coil. The normally closed contacts of the first n-1 DC relays are connected in series in sequence. 1 The other end of the coil is connected to the other end of its normally closed contact and connected to the second DC power supply V c2 The positive terminal of the second DC relay J 2 , ..., n-1th DC relay J n-1 The other end of the coil is connected to the normally closed contact of the DC relay and the normally closed contact of the previous DC relay. n The other end of the coil is connected to the n-1th DC relay J n-1 At the other end of the normally closed contact, the emitter of each NPN transistor is connected through a resistor R E1 , …, R En The DC relay control module is used to drive the corresponding DC relay according to the interval marking signal received by the NPN transistor. The DC relay controls the integrated operational amplifier module to select the feedback branch by closing the normally open contact to obtain different gains.

[0063] Preferably, each DC relay coil is connected with a diode in anti-parallel.

[0064] The integrated operational amplifier module includes an integrated operational amplifier and n parallel feedback branches, wherein each feedback branch is composed of a feedback resistor and a normally open contact of a DC relay in series, and the n feedback branches correspond to n different gains due to different feedback resistors; the DC voltage signal output by the signal acquisition and conversion module passes through the in-phase resistor R p The input is sent to the non-inverting input of the integrated operational amplifier, and the inverting input of the integrated operational amplifier passes through the inverting resistor R m The integrated operational amplifier is grounded, and the output end of the integrated operational amplifier is connected to the inverting input end of the integrated operational amplifier through a feedback branch, and the output end of the integrated operational amplifier is connected to the ADC module of the DSP; the integrated operational amplifier module is used to amplify the DC voltage signal to generate a leakage current sampling value within the normal working range of the ADC module of the DSP and output it.

[0065] Preferably, a diode connected end to end is added to the output end of the integrated operational amplifier, wherein the cathode of the diode connected to the output end of the integrated operational amplifier is connected to the third DC power supply V c3 The positive terminal of the diode connected to the output terminal of the integrated operational amplifier is grounded, thereby limiting the output of the integrated operational amplifier to 0~V c3 Between (V c3 >0), V c3 It should be determined according to the allowable range of the DSP ADC port input voltage to protect the DSP ADC port.

[0066] The level conversion circuit is used to convert a leakage current interval marking signal composed of output levels of n integrated voltage comparators into an input signal within a normal working range of a general purpose input / output multiplexer (GPIO) of a DSP.

[0067] Embodiment 2 of the present invention provides a method for measuring motor insulation leakage current, which uses the motor insulation leakage current segmented variable gain amplifier circuit as described in Embodiment 1 to measure the motor insulation leakage current, and includes the following steps:

[0068] Step 1: collect the original AC motor leakage current and transform it into a DC voltage signal corresponding to the effective value of the leakage current.

[0069] Preferably, a zero-flux leakage current sensor is used to convert the sinusoidal AC leakage current of the AC motor with a wide detection range into a sinusoidal AC voltage signal, which is then converted into a DC voltage signal linearly related to the leakage current effective value via an AC small signal amplifier and a full-wave rectifier sinusoidal effective value circuit.

[0070] Step 2: Set the reference voltage value of the boundary of the leakage current n intervals, and obtain the interval marking signal (a) according to the segmented interval i where the DC voltage signal obtained in step 1 is located. 1 , a 2 , …, a i , …, a n ), where a 1 , …, a i-1 =0,a i , …, a n =1, and amplify the corresponding multiple to obtain the leakage current sampling value.

[0071] Specifically, the DC voltage signal of step 1 is compared with the reference voltage values ​​of n interval boundaries through n integrated voltage comparators to obtain the interval marking signal of the leakage current, and drive the corresponding DC relay, so that the integrated operational amplifier feedback branch is connected to the corresponding feedback resistor, and the amplification factor of the operational amplifier is automatically adjusted online to obtain the leakage current sampling value within the normal working range of the ADC module of the DSP.

[0072] In a preferred but non-limiting embodiment of the present invention, by properly selecting n resistors R 1 , R 2 , …, R n The size of the leakage current is obtained by using a voltage divider circuit composed of n resistors in series to obtain the reference voltage value of the boundary of the n intervals of the leakage current. The reference voltage value of the interval boundary of the segmented interval i is expressed by the following formula:

[0073]

[0074] V i上 =V i-1下

[0075] Where:

[0076] V i下 Represents the lower limit of the reference voltage value of segment interval i;

[0077] V i上 Represents the upper limit of the reference voltage value of segment interval i;

[0078] |V c1 | is the voltage value of the first DC power supply (Vc1).

[0079] In an exemplary but non-limiting embodiment, when the leakage current measurement signal is in the maximum value interval (first interval), the voltage values ​​of the in-phase input terminals of the integrated voltage comparator 1, the integrated voltage comparator 2, ..., and the integrated voltage comparator n are all greater than the voltage value of the inverting input terminal, and the output levels of the n integrated voltage comparators are all high levels, and the corresponding interval marking signal of the segment where the leakage current is located is (1, 1, ..., 1);

[0080] When the leakage current measurement signal is in the second interval segment, the voltage value of the non-inverting input terminal of the integrated voltage comparator 1 is less than the voltage value of its inverting input terminal, and the integrated voltage comparator 1 outputs a low level, while the voltage values ​​of the non-inverting input terminals of the integrated voltage comparators 2, ..., and integrated voltage comparators n are all greater than the voltage value of the inverting input terminals, so the output levels are all high levels, and the corresponding interval marking signal of the segment where the leakage current is located is (0, 1, ..., 1);

[0081] By analogy, when the leakage current measurement signal is in the minimum value interval (nth interval), the voltage values ​​of the non-inverting input terminals of integrated voltage comparator 1, integrated voltage comparator 2, ..., integrated voltage comparator n-1 are all smaller than the voltage values ​​of their inverting input terminals, so the outputs are all low level, while the voltage value of the non-inverting input terminal of integrated voltage comparator n is larger than the voltage value of the inverting input terminal, so the output level is high level, and the corresponding interval marking signal of the leakage current segment is (0, ..., 0, 1).

[0082] It is understandable that the use of Figure 1 The voltage divider circuit composed of n resistors connected in series and n comparators and relays shown can automatically switch n different feedback resistors of the feedback branch of the integrated operational amplifier according to the n-level segmented intervals of the leakage current, thereby realizing online automatic adjustment of the amplification factor of the operational amplifier.

[0083] In a preferred but non-limiting embodiment of the present invention, in order to ensure that both the large leakage current signal and the small leakage current signal can be reasonably amplified to the analog signal allowable range of the ADC module of the DSP, the R F1 <R F2 <… <R FnThe principle and actual leakage current measurement range are used to reasonably set the number of stages n of the segmented interval and the corresponding feedback resistance R of the operational amplifier feedback branch. F1 , R F2 , …, R Fn .

[0084] Step 3, calculating the effective value of the original AC motor leakage current according to the interval marking signal and the leakage current sampling value obtained in step 2.

[0085] In a preferred but non-limiting embodiment of the present invention, the leakage current interval mark signal composed of the output levels of n integrated voltage comparators is converted into an input signal within the normal working range of the DSP GPIO by a level conversion circuit, and the DSP program is executed according to the Figure 2 The subroutine flowchart shown in the figure realizes accurate restoration of the original wide range AC leakage current effective value through the leakage current interval marking signal and the leakage current sampling value. Step 3 specifically includes:

[0086] Step 3.1, read the leakage current sampling value and the interval marking signal;

[0087] Step 3.2, obtaining the corresponding amplification factor according to the interval marking signal;

[0088] Further preferably, the feedback resistor connected to the integrated operational amplifier feedback branch is determined according to the interval marking signal, thereby obtaining the corresponding amplification factor, and the operational amplifier feedback branch feedback resistor R F1 , R F2 , …, R Fn And the op amp gain K 1 , K 2 , …, K n The corresponding relationship is expressed by the following formula:

[0089]

[0090] Where:

[0091] K j Indicates the integrated operational amplifier gain corresponding to the jth interval of the leakage current;

[0092] R Fj represents the feedback resistance value of the jth feedback branch;

[0093] |R m | represents the resistance value connected to the ground of the inverting input terminal of the integrated operational amplifier, that is, the size of the inverting resistance Rm.

[0094] In an exemplary but non-limiting embodiment, when the leakage current measurement signal is in the maximum interval (first interval), the interval marking signal of the corresponding leakage current segment obtained according to step 2 is (1, 1, ..., 1), at this time, the transistor VT1 Forward conduction, small DC relay J 1 When it is powered on, its normally closed contact opens, cutting off the small DC relay J 2 , …, J n The power supply J 1 The normally open contact of is closed, and the integrated operational amplifier feedback branch is connected to the corresponding feedback resistor R F1 , the corresponding magnification K 1 =(1+R F1 / |R m |);

[0095] When the leakage current measurement signal is in the second interval, the interval marking signal of the corresponding leakage current segment obtained in step 2 is (0, 1, ..., 1). At this time, the transistor VT 2 Forward conduction, DC relay J 2 When it is powered on, its normally closed contact opens, cutting off the small DC relay J 3 , …, J n The power supply J 2 The normally open contact of is closed, and the integrated operational amplifier feedback branch is connected to the corresponding feedback resistor R F2 , the corresponding magnification K 2 =(1+R F2 / |R m |);

[0096] Similarly, when the leakage current measurement signal is in the minimum value interval (nth interval), the interval marking signal of the corresponding leakage current segment obtained according to step 2 is (0, ..., 0, 1). At this time, the transistor VT n Forward conduction, small DC relay J n When powered on, its normally open contact is closed, and the integrated operational amplifier feedback branch is connected to the corresponding feedback resistor R Fn , the corresponding magnification K n =(1+R Fn / |R m |).

[0097] Step 3.3, based on the zero-flux leakage current sensor, the AC small signal amplifier, and the full-wave rectified sinusoidal effective value circuit parameters, combined with the leakage current sampling value of step 3.1 and the amplification factor of step 3.2, calculate the effective value of the original AC motor leakage current.

[0098] Further preferably, according to the relationship between the analog voltage input to the ADC module of the DSP and the leakage current sampling value, the ADC input analog signal is obtained from the leakage current sampling value, that is, the integrated operational amplifier output signal V F , calculate the effective value of the original AC motor leakage current according to the following formula:

[0099]

[0100] Where:

[0101] I LC Indicates the effective value of the original AC motor leakage current;

[0102] V F It represents the integrated operational amplifier output signal, that is, the ADC input analog signal, which is calculated by the leakage current sampling value. When the leakage current sampling value is between 0 and V c3 Between V F Equal to the leakage current sampling value;

[0103] G LC It represents the conversion coefficient between the input current and the output voltage of the zero flux leakage current sensor, which is obtained from the performance parameters of the zero flux leakage current sensor;

[0104] G AC It indicates the gain of the AC small signal amplifier, which is determined by its circuit parameters;

[0105] G rms It represents the transformation coefficient of the full-wave rectifier sine effective value circuit. By setting the circuit parameters reasonably, G rms Can be 1.

[0106] Compared with the prior art, the beneficial effects of the present invention include at least: compared with the conventional variable gain amplifier, the technical solution proposed by the present invention and its specific circuit have the advantages of simple structure, low cost, large gain variation range, and accurate restoration of the original wide range AC leakage current effective value, etc., which is suitable for the long-term online monitoring of AC motor stator insulation based on leakage current detection.

[0107] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A motor insulation leakage current segmented variable gain amplifier circuit, characterized in that: include: Signal acquisition and conversion module, series voltage division module, integrated voltage comparison module, DC relay control module, integrated operational amplifier module and level conversion circuit; The signal acquisition and conversion module includes: a zero-flux leakage current sensor, an AC small signal amplifier, and a full-wave rectified sinusoidal effective value circuit. The signal acquisition and conversion module is used to acquire and convert the AC motor leakage current into a DC voltage signal corresponding to the effective value of the leakage current; The series voltage divider module includes n series-connected resistors, and the series voltage divider module is used to use the divided voltage of each resistor as the reference voltage value of the boundary of n leakage current intervals; The integrated voltage comparison module includes n integrated voltage comparators, and the integrated voltage comparison module is used to segment the DC voltage signal according to the comparison result between the DC voltage signal and the reference voltage values ​​at the boundaries of the n intervals, so as to obtain the interval marking signal of the leakage current; The DC relay control module includes n DC relays and corresponding n transistors for controlling whether the DC relays work or not. The DC relay control module is used to control the integrated operational amplifier module to select a feedback branch according to the interval marking signal to obtain different gains. The integrated operational amplifier module includes an integrated operational amplifier and n parallel feedback branches, the n feedback branches correspond to n different gains, and the integrated operational amplifier module is used to amplify the DC voltage signal to generate a leakage current sampling value within the normal working range of the analog / digital converter and output it; The level conversion circuit is used to convert the interval mark signal into an input signal within the normal working range of the general input / output multiplexer.

2. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 1, characterized in that: The series voltage divider module is composed of n resistors, a first resistor, a second resistor, ..., and an nth resistor connected in series. One end of the first resistor of the series voltage divider module is connected to the positive end of the first DC power supply, and the other end is connected to one end of the second resistor. One end of the nth resistor is connected to one end of the n-1th resistor, and the other end is grounded.

3. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 1, characterized in that: The integrated voltage comparison module is composed of n integrated voltage comparators, the inverting input terminals of the first integrated voltage comparator, the second integrated voltage comparator, ..., and the n-1th integrated voltage comparator are respectively connected between the first resistor and the second resistor, between the second resistor and the third resistor, ..., between the n-1th resistor and the nth resistor, the inverting input terminal of the nth integrated voltage comparator is grounded, and the DC voltage signal output by the signal acquisition and conversion module is input to the non-inverting input terminals of the n integrated voltage comparators through the resistor.

4. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 1, characterized in that: In the DC relay control module, the transistor is an NPN transistor, and the DC relay includes a coil, a normally open contact and a normally closed contact. The DC relay control module receives the interval marking signal through the NPN transistor and drives the corresponding DC relay. The DC relay controls the integrated operational amplifier module to select the feedback branch by closing the normally open contact.

5. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 4, characterized in that: The base of each NPN transistor is connected to the output terminal of the integrated voltage comparator through a resistor; The collector of each NPN transistor is connected to one end of the corresponding DC relay coil, the normally closed contacts of the first n-1 DC relays are connected in series in sequence, the other end of the first DC relay coil is connected to the other end of its normally closed contact and connected to the positive end of the second DC power supply, the other ends of the second DC relay, ..., the n-1th DC relay coils are respectively connected between the normally closed contact of the DC relay and the normally closed contact of the previous DC relay, and the other end of the nth DC relay coil is connected to the other end of the normally closed contact of the n-1th DC relay; The emitter of each NPN transistor is connected to ground through a resistor.

6. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 5, characterized in that: Each DC relay coil is connected in anti-parallel with a diode.

7. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 1 or 4, characterized in that: In the integrated operational amplifier module, the feedback branch is composed of a feedback resistor and a normally open contact of a DC relay in series; the DC voltage signal output by the signal acquisition and conversion module is input to the in-phase input terminal of the integrated operational amplifier through a in-phase resistor, the inverting input terminal of the integrated operational amplifier is grounded through an inverting resistor, the output terminal of the integrated operational amplifier is connected to the inverting input terminal of the integrated operational amplifier through a feedback branch, and the output terminal of the integrated operational amplifier is connected to the ADC module of the DSP.

8. The motor insulation leakage current segmented variable gain amplifier circuit according to claim 7, characterized in that: A diode connected end to end is added to the output end of the integrated operational amplifier, wherein the cathode of the diode whose anode is connected to the output end of the integrated operational amplifier is connected to the positive end of the third DC power supply, and the anode of the diode whose cathode is connected to the output end of the integrated operational amplifier is grounded.

9. A method for measuring motor insulation leakage current, using the motor insulation leakage current segmented variable gain amplifier circuit as claimed in any one of claims 1 to 8 to achieve the measurement of motor insulation leakage current, characterized in that: The following steps are involved: Step 1, collecting the original AC motor leakage current and converting it into a DC voltage signal corresponding to the effective value of the leakage current; Step 2, set the reference voltage value of the leakage current n interval boundaries, and obtain the interval marking signal a1, a2, ..., a according to the segmented interval i where the DC voltage signal obtained in step 1 is located. i , …, a n , where a1,…,a i-1 =0,a i , …, a n =1, and amplify the corresponding multiple to obtain the leakage current sampling value; Step 3, calculating the effective value of the original AC motor leakage current according to the interval marking signal and the leakage current sampling value obtained in step 2.

10. The motor insulation leakage current measurement method according to claim 9, characterized in that: In step 2, the sizes of the first resistor, the second resistor, ..., and the nth resistor are selected, and a voltage divider circuit consisting of n resistors connected in series is used to obtain reference voltage values ​​of the boundaries of n intervals of the leakage current, wherein the reference voltage value of the interval boundary of the segmented interval i is expressed by the following formula: V i上 =V i-1下 Where: V i下 Represents the lower limit of the reference voltage value of segment interval i; V i上 Represents the upper limit of the reference voltage value of segment interval i; V c1 | is the voltage value of the first DC power supply.

11. The method for measuring motor insulation leakage current according to claim 9, characterized in that: Step 3 specifically includes: Read the leakage current sampling value and the interval marking signal; According to the interval marking signal, the feedback resistor connected to the integrated operational amplifier feedback branch is determined, and then the corresponding amplification factor is obtained. The feedback resistor R F1 , R F2 , …, R Fn And the op amp gain K1, K2, ..., K n The corresponding relationship is expressed by the following formula: K j =(1+R Fj / |R m |) Where: R Fj represents the feedback resistance value of the jth feedback branch; |R m | represents the resistance value connected to the ground of the inverting input terminal of the integrated operational amplifier; According to the zero-flux leakage current sensor, AC small signal amplifier, and full-wave rectified sinusoidal effective value circuit parameters, the effective value of the original AC motor leakage current is calculated by combining the leakage current sampling value and the amplification factor.

12. The motor insulation leakage current measurement method according to claim 11, characterized in that: According to the relationship between the analog voltage input to the DSP ADC module and the leakage current sampling value, the integrated operational amplifier output signal V is obtained from the leakage current sampling value. F , calculate the effective value of the original AC motor leakage current according to the following formula: Where: I LC Indicates the effective value of the original AC motor leakage current; V F Represents the integrated operational amplifier output signal; G LC Indicates the conversion coefficient between the input current and output voltage of the zero flux leakage current sensor; G AC Indicates the amplification factor of the AC small signal amplifier; G rms Indicates the transformation coefficient of the full-wave rectified sine effective value circuit, G rms =1.

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