Electric leakage detection circuit applied to motor protection

Abstract

The invention discloses an electric leakage detection circuit applied to motor protection, which comprises an electric leakage current transformer arranged on a motor power supply line, and electric leakage signal detection ports COM3 and IL * which are respectively arranged on an intelligent motor protector and are correspondingly connected with two ends of a secondary side winding outgoing line of the electric leakage current transformer, the input / output interface IO + and IO-are respectively arranged on the intelligent motor protector; the electric leakage detection active intervention current line passes through the current transformer; the two ends of the electric leakage detection active intervention current line are correspondingly connected to an input / output interface IO + and IO-on the intelligent motor protector respectively, and an intervention current output circuit used for generating an intervention current for electric leakage detection is arranged between the input / output interface IO + and IO-of the intelligent motor protector and a PWM signal output interface PTC of the single-chip microcomputer. According to the invention, maintainers can be helped to analyze reasons of abnormity or inaccurate electric leakage values, and the reliability of electric leakage detection of the intelligent motor protector is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor protection, and particularly relates to a leakage detection circuit applied to motor protection. Background Art

[0002] An intelligent motor protector is a device used for motor protection. The intelligent motor protector uses a built-in current transformer to detect the current change in the motor power supply line. When there is a leakage phenomenon in the motor, the current will flow to the ground through an abnormal path, resulting in current imbalance. The protector detects this imbalance to identify the leakage situation and quickly cuts off the power supply to prevent safety accidents such as fires and electric shocks caused by leakage. In order to improve the reliability of leakage detection, an external current transformer connected to the intelligent motor protector can also be used for leakage detection.

[0003] However, the existing intelligent motor protectors still have the following deficiencies: When the leakage function is abnormal or the leakage value is inaccurate, it is very difficult for maintenance personnel to judge the reason on site, whether there is a leakage current in the detected circuit or the test data is abnormal due to a fault in the intelligent motor protector. Summary of the Invention

[0004] In order to solve the above problems, the present invention proposes a leakage detection circuit applied to motor protection, aiming to help maintenance personnel analyze the reasons for abnormalities or inaccurate leakage values and improve the reliability of leakage detection of intelligent motor protectors. The specific technical solutions are as follows: A leakage detection circuit applied to motor protection includes an intelligent motor protector, a single-chip microcomputer arranged in the intelligent motor protector, a PWM signal output interface PTC arranged on the single-chip microcomputer, a leakage current transformer arranged on the motor power supply line for detecting the leakage situation of the motor, a leakage signal detection port COM3 and a leakage signal detection port IL* respectively arranged on the intelligent motor protector and correspondingly connected to both ends of the lead-out wire of the secondary side winding of the leakage current transformer, an input / output interface IO+ and an input / output interface IO- respectively arranged on the intelligent motor protector, and a leakage detection active intervention current line passing through the current transformer; both ends of the leakage detection active intervention current line are correspondingly connected to the input / output interface IO+ and the input / output interface IO- on the intelligent motor protector, and an intervention current output circuit for generating an intervention current for leakage detection is arranged between the input / output interface IO+ and the input / output interface IO- on the intelligent motor protector and the PWM signal output interface PTC of the single-chip microcomputer.

[0005] Preferably, the interference current output circuit includes an opto-coupled isolation signal output circuit module for outputting the PWM signal output by the single-chip microcomputer after opto-coupled isolation, and a PWM AC current output circuit module for converting the opto-coupled isolated PWM signal IL_0 output by the isolation signal output circuit module into the AC current required for the leakage detection active interference current line.

[0006] Preferably, the opto-coupled isolation signal output circuit module includes an opto-coupler U13 composed of a mutually coupled light-emitting diode and a phototransistor. The PWM signal output interface PTC of the single-chip microcomputer is connected to the negative terminal of the light-emitting diode of the opto-coupler U13, and the positive terminal of the phototransistor of the opto-coupler U13 outputs the opto-coupled isolated PWM signal IL_0; the positive terminal of the phototransistor of the opto-coupler U13 is connected to the positive pole of the DC power supply V through a resistor R32, and the positive terminal of the light-emitting diode of the opto-coupler U13 is connected to the positive pole of the DC power supply V2 through a resistor R35.

[0007] Preferably, the interference current output circuit further includes a leakage detection interference current generation circuit module for providing an AC current for the leakage detection active interference current line. The leakage detection interference current generation circuit module includes transistors Q1, Q2, and Q3. The positive terminal of the phototransistor of the opto-coupler U13 is connected to the base of the transistor Q3 through a resistor R41. The collector of the transistor Q3 is connected to the collectors of the transistors Q1 and the base of the transistor Q2 through a resistor R38. The emitter of the transistor Q1 is connected to the positive pole of the DC power supply V2, and the emitter of the transistor Q2 is connected to the base of the transistor Q1; a resistor R43 is connected between the base and the emitter of the transistor Q3, a resistor R31 is connected between the emitter and the collector of the transistor Q1, and a resistor R6 is connected between the emitter and the base of the transistor Q1; the collector of the transistor Q2 is connected to the input / output interface IO+ on the intelligent motor protector, and the connection end of the emitter of the transistor Q3 and the resistor R43 is connected to the input / output interface IO- on the intelligent motor protector through a resistor R45.

[0008] Preferably, the intervention current output circuit further includes an isolated power supply circuit module for providing a DC power supply V2 to the opto-coupled isolation signal output circuit module and the leakage detection intervention current generation circuit module; the isolated power supply circuit module includes a push-pull control chip IC1, a transformer T1, and a dummy load R36. The power input terminal VIN of the push-pull control chip IC1 is connected to the positive pole of the DC power supply and grounded through a capacitor C3. The center tap of the primary side winding of the transformer T1 is connected to the positive pole of the DC power supply. The two ends of the primary side winding of the transformer T1 are respectively connected to the push-pull output terminals VD1 and VD2 of the push-pull control chip IC1. The secondary side windings of the transformer T1 are respectively connected to one end of the dummy load R36 through diodes D1 and D2. The center tap of the secondary side winding of the transformer T1 is connected to the other end of the dummy load R36. A capacitor C1 is connected in parallel between the two ends of the dummy load.

[0009] In the present invention, a leakage detection conversion circuit is further connected between the leakage signal detection port COM3 and the leakage signal detection port IL* of the intelligent motor protector and the ADC interface of the single-chip microcomputer. The leakage detection conversion circuit includes a leakage signal conversion circuit module for converting the secondary side leakage current measured by the leakage current transformer into a voltage signal IL and a leakage signal amplification processing circuit module for amplifying and processing the voltage signal IL. The leakage signal conversion circuit module includes an inductor L7, an inductor L6, a resistor R14, and a capacitor C25. One end of the inductor L7 is connected to the leakage signal detection port COM3. One end of the inductor L6 is connected to the leakage signal detection port IL*. The end of the inductor L7 connected to the leakage signal detection port IL* is also connected to the ground terminal GND through the capacitor C25. The other end of the inductor L6 is connected in parallel with the other end of the inductor L6 through the resistor R14 to form a parallel connection end, and a reference voltage VARF2 is applied to the parallel connection end. The voltage signal IL is generated at the connection part between the inductor L6 and the resistor R14.

[0010] Preferably, the leakage signal amplification and processing circuit module includes an operational amplifier ICD3, resistors R8, R7, R5, a capacitor C11, a clamping diode D2, and a capacitor C7. The positive input pin of the operational amplifier ICD3 is loaded with a reference voltage VARF2. The negative input pin of the operational amplifier ICD3 is connected through the resistor R8 to the connection part between the inductor L6 and the resistor R14 in the leakage signal conversion circuit module. A resistor R7 is also connected between the negative input pin and the output pin of the operational amplifier ICD3. The output pin of the operational amplifier ICD3 is connected to the clamping diode D2 through the resistor R5. One end of the operational amplifier ICD3 is loaded with a positive voltage and the other end is grounded. The connection end of the resistor R5 and the clamping diode D2 is also connected to the ground terminal through the capacitor C7. An amplified processing voltage ILP is formed at the connection end of the resistor R5 and the clamping diode D2.

[0011] Preferably, the leakage detection and conversion circuit further includes a reference voltage generation circuit module. The reference voltage generation circuit module includes an operational amplifier IC1A, capacitors C1, C2, a resistor R1, and a resistor array RR1 composed of a plurality of resistors. The positive power supply terminal of the operational amplifier IC1A is loaded with a positive voltage and is connected to the ground terminal through the capacitor C1. The negative power supply terminal of the operational amplifier IC1A is connected to the ground terminal. The positive input pin of the operational amplifier IC1A is loaded with a positive voltage through the resistor array RR1. The output pin of the operational amplifier IC1A is sequentially connected to the ground terminal through the resistor R1 and the capacitor C2. The connection part between the resistor R1 and the capacitor C2 is connected to the negative input pin of the operational amplifier IC1A and the reference voltage VARF2 is formed at the connection part between the resistor R1 and the capacitor C2.

[0012] In the present invention, the amplified processing voltage ILP formed at the connection end of the resistor R5 and the clamping diode D2 is IL*(1 + R7 / R8).

[0013] In the present invention, the connection end of the resistor R5 and the clamping diode D2 is connected to the ADC interface of the single-chip microcomputer.

[0014] The beneficial effects of the present invention are: A leakage detection circuit for motor protection according to the present invention specially provides an interference current output circuit for generating an interference current for leakage detection inside an intelligent motor protector. The interference current output circuit can output an alternating current of 50 mA. During operation, the single-chip microcomputer can control the interference current output circuit to output or not output the alternating current, thereby forming two leakage current detection modes: non-interference detection mode and interference detection mode. By comparing the leakage data measured by the external current transformer in the two detection modes, it can be determined whether there is a leakage current in the detected line or the test data is abnormal due to a fault in the intelligent motor protector, thereby realizing the comprehensive detection of the leakage function. This greatly facilitates the customer to test the leakage function and enables the operation and maintenance personnel and the maintenance personnel to easily troubleshoot problems on-site without contacting the manufacturer of the motor protector to determine the cause of the fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the overall solution of a leakage detection circuit for motor protection according to the present invention; Figure 2 is a schematic diagram of the leakage detection conversion circuit; Figure 3 is a schematic diagram of the interference current output circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The following will further describe the specific embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0017] Such as Figures 1 to 3An embodiment of a leakage detection circuit for motor protection according to the present invention is shown, including an intelligent motor protector, a single-chip microcomputer disposed in the intelligent motor protector, a PWM signal output interface PTC disposed on the single-chip microcomputer, a leakage current transformer disposed on the motor power supply line for detecting the leakage condition of the motor, a leakage signal detection port COM3 and a leakage signal detection port IL* respectively disposed on the intelligent motor protector and correspondingly connected to both ends of the secondary side winding lead-out wire of the leakage current transformer, an input / output interface IO+ and an input / output interface IO- respectively disposed on the intelligent motor protector, and a leakage detection active intervention current line passing through the current transformer; both ends of the leakage detection active intervention current line are respectively correspondingly connected to the input / output interface IO+ and the input / output interface IO- on the intelligent motor protector, and an intervention current output circuit for generating an intervention current for leakage detection is disposed between the input / output interface IO+ and the input / output interface IO- of the intelligent motor protector and the PWM signal output interface PTC of the single-chip microcomputer.

[0018] Preferably, the intervention current output circuit includes an opto-coupled isolation signal output circuit module for outputting the PWM signal output by the single-chip microcomputer after opto-coupled isolation, and a PWM AC current output circuit module for converting the opto-coupled isolated PWM signal IL_0 output by the isolation signal output circuit module into the AC current required for the leakage detection active intervention current line.

[0019] Preferably, the opto-coupled isolation signal output circuit module includes an opto-coupler U13 composed of a mutually coupled light-emitting diode and a phototransistor. The PWM signal output interface PTC of the single-chip microcomputer is connected to the negative electrode of the light-emitting diode of the opto-coupler U13, and the positive electrode of the phototransistor of the opto-coupler U13 outputs the opto-coupled isolated PWM signal IL_0; the positive electrode of the phototransistor of the opto-coupler U13 is connected to the positive electrode of the DC power supply V through a resistor R32, and the positive electrode of the light-emitting diode of the opto-coupler U13 is connected to the positive electrode of the DC power supply V2 through a resistor R35.

[0020] Preferably, the intervention current output circuit further includes a leakage detection intervention current generation circuit module for providing an alternating current to the leakage detection active intervention current line. The leakage detection intervention current generation circuit module includes transistors Q1, Q2, and Q3. The positive terminal of the phototransistor of the optocoupler U13 is connected to the base of transistor Q3 through resistor R41. The collector of transistor Q3 is connected to the collectors of transistor Q1 and the base of transistor Q2 through resistor R38. The emitter of transistor Q1 is connected to the positive pole of the DC power supply V2. The emitter of transistor Q2 is connected to the base of transistor Q1. A resistor R43 is connected between the base and emitter of transistor Q3. A resistor R31 is connected between the emitter and collector of transistor Q1. A resistor R6 is connected between the emitter and base of transistor Q1. The collector of transistor Q2 is connected to the input / output interface IO+ on the intelligent motor protector. The connection end of the emitter of transistor Q3 and resistor R43 is connected to the input / output interface IO- on the intelligent motor protector through resistor R45.

[0021] Preferably, the intervention current output circuit further includes an isolated power supply circuit module for providing the DC power supply V2 to the opto-coupled isolation signal output circuit module and the leakage detection intervention current generation circuit module. The isolated power supply circuit module includes a push-pull control chip IC1, a transformer T1, and a dummy load R36. The power input terminal VIN of the push-pull control chip IC1 is connected to the positive pole of the DC power supply and grounded through capacitor C3. The center tap of the primary side winding of the transformer T1 is connected to the positive pole of the DC power supply. The two ends of the primary side winding of the transformer T1 are respectively connected to the push-pull output terminals VD1 and VD2 of the push-pull control chip IC1. The secondary side windings of the transformer T1 are respectively connected to one end of the dummy load R36 through diodes D1 and D2. The center tap of the secondary side winding of the transformer T1 is connected to the other end of the dummy load R36. A capacitor C1 is connected in parallel between the two ends of the dummy load.

[0022] In this embodiment, a leakage detection conversion circuit is further connected between the leakage signal detection port COM3 and the leakage signal detection port IL* of the intelligent motor protector and the ADC interface of the single-chip microcomputer. The leakage detection conversion circuit includes a leakage signal conversion circuit module for converting the secondary-side leakage current measured by the leakage current transformer into a voltage signal IL, and a leakage signal amplification processing circuit module for amplifying and processing the voltage signal IL. The leakage signal conversion circuit module includes an inductor L7, an inductor L6, a resistor R14, and a capacitor C25. One end of the inductor L7 is connected to the leakage signal detection port COM3, one end of the inductor L6 is connected to the leakage signal detection port IL*, and the end of the inductor L7 connected to the leakage signal detection port IL* is also connected to the ground terminal GND through the capacitor C25. The other end of the inductor L6 is connected to the other end of the inductor L6 through the resistor R14 to form a parallel connection end, and a reference voltage VARF2 is applied to the parallel connection end. The voltage signal IL is generated at the connection part between the inductor L6 and the resistor R14.

[0023] Preferably, the leakage signal amplification processing circuit module includes an operational amplifier ICD3, resistors R8, R7, R5, a capacitor C11, a clamping diode D2, and a capacitor C7. The positive input pin of the operational amplifier ICD3 is applied with a reference voltage VARF2. The negative input pin of the operational amplifier ICD3 is connected to the connection part between the inductor L6 and the resistor R14 in the leakage signal conversion circuit module through the resistor R8. A resistor R7 is also connected between the negative input pin and the output pin of the operational amplifier ICD3. The output pin of the operational amplifier ICD3 is connected to the clamping diode D2 through the resistor R5. One end of the operational amplifier ICD3 is applied with a positive voltage and the other end is grounded. The connection end of the resistor R5 and the clamping diode D2 is also connected to the ground terminal through the capacitor C7. An amplified processing voltage ILP is formed at the connection end of the resistor R5 and the clamping diode D2.

[0024] Preferably, the leakage detection conversion circuit further includes a reference voltage generation circuit module. The reference voltage generation circuit module includes an operational amplifier IC1A, capacitors C1 and C2, a resistor R1, and a resistor network RR1 composed of a plurality of resistors. The positive power supply terminal of the operational amplifier IC1A is loaded with a positive voltage and connected to the ground terminal through the capacitor C1. The negative power supply terminal of the operational amplifier IC1A is connected to the ground terminal. The positive input pin of the operational amplifier IC1A is loaded with a positive voltage through the resistor network RR1. The output pin of the operational amplifier IC1A is connected to the ground terminal through the resistor R1 and the capacitor C2 in sequence. The connection part between the resistor R1 and the capacitor C2 is connected to the negative input pin of the operational amplifier IC1A, and the reference voltage VARF2 is formed at the connection part between the resistor R1 and the capacitor C2.

[0025] In this embodiment, the amplified processing voltage ILP formed at the connection end of the resistor R5 and the clamping diode D2 is ILP = IL * (1 + R7 / R8).

[0026] In this embodiment, the connection end of the resistor R5 and the clamping diode D2 is connected to the ADC interface of the single-chip microcomputer.

[0027] Figure 2 In the leakage detection conversion circuit, the 5th and 6th cores on the external terminal J2 are connected to the secondary side of the external leakage current transformer. There is an mA-level alternating current at the leakage signal detection ports IL* and COM3. After passing through L6, L7, and R14, the alternating current signal is converted into a voltage signal IL, and C25 is a filtering capacitor.

[0028] VREF2 is a 1.65V voltage reference. After the 3.3V voltage is divided by the resistor network RR1, it enters the operational amplifier IC1A. The function of the operational amplifier IC1A is voltage following. The voltage output from pin 1 passes through a first-stage RC filter and then outputs VREF2; The voltage signal IL is inversely amplified by the operational amplifier IC3D to obtain the signal ILP. ILP is connected to the ADC interface of the single-chip microcomputer for signal processing and calculation. The amplification calculation formula of the IC3D operational amplifier is: ILP = IL * (1 + R7 / R8); C11 is a filtering capacitor at the input end of the operational amplifier, R5 and C7 form a first-stage RC filter circuit, and D2 is a clamping diode.

[0029] Figure 3 In the interference current output circuit, IC1, T1, D1, D2, C1, and R36 form a 5V to 5V isolated power supply circuit module. IC1 is a push-pull control chip, T1 is a transformer, D1 and D2 are rectifier diodes, C1 is a filtering capacitor, and R36 is a dummy load.

[0030] R35, R32, and U13 form an opto-coupled isolation signal output circuit module. Its function is to isolate the PWM signal output by the single-chip microcomputer (network PTC in the figure) through opto-coupler U13 and output IL_0. R35 and R32 are pull-up resistors.

[0031] After the isolated output PWM signal IL_O passes through the circuit composed of transistors Q1, Q2, and Q3, an alternating current is output and output through the IO+ and IO- terminals. The function of Q3 in the circuit is to control the on / off of the constant current source circuit. Q1 and Q2 form a constant current source circuit, and R45 is a current-limiting resistor. In this stage, to adjust the output current, the software can control the waveform of the output PWM by the single-chip microcomputer to adjust the current, and the hardware can also change the output current by adjusting the resistance values of R45 and R6.

[0032] The above is only the preferred implementation mode of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A leakage detection circuit for motor protection, characterized in that: It includes an intelligent motor protector, a single-chip microcomputer arranged in the intelligent motor protector, a PWM signal output interface PTC arranged on the single-chip microcomputer, a leakage current transformer arranged on the motor power supply line for detecting the leakage of the motor, a leakage signal detection port COM3 and a leakage signal detection port IL* respectively arranged on the intelligent motor protector and correspondingly connected to the two ends of the secondary side winding lead-out line of the leakage current transformer, an input / output interface IO+ and an input / output interface IO- respectively arranged on the intelligent motor protector, and a leakage detection active intervention current line passing through the current transformer; The two ends of the leakage detection active intervention current line are respectively connected to the input / output interface IO+ and the input / output interface IO- on the intelligent motor protector, and an intervention current output circuit for generating an intervention current for leakage detection is arranged between the input / output interface IO+ and the input / output interface IO- of the intelligent motor protector and the PWM signal output interface PTC of the single-chip computer.

2. A leakage detection circuit for motor protection according to claim 1, characterized in that: The intervention current output circuit includes an optocoupler isolation signal output circuit module for outputting the PWM signal output by the single-chip microcomputer after optocoupler isolation, and a PWM AC current output circuit module for converting the optocoupler isolation PWM signal IL_0 output by the isolation signal output circuit module into the AC current required for the leakage detection active intervention current line.

3. A leakage detection circuit for motor protection according to claim 2, characterized in that: The optically coupled isolation signal output circuit module includes a photoelectric coupler U13 composed of a mutually coupled light-emitting diode and a phototransistor, the PWM signal output interface PTC of the single-chip computer is connected to the negative terminal of the light-emitting diode of the photoelectric coupler U13, and the positive terminal of the phototransistor of the photoelectric coupler U13 outputs the optically coupled isolation PWM signal IL_0; the positive terminal of the phototransistor of the photoelectric coupler U13 is connected to the positive electrode of the DC power supply V through a resistor R32, and the positive terminal of the light-emitting diode of the photoelectric coupler U13 is connected to the positive electrode of the DC power supply V2 through a resistor R35.

4. A leakage detection circuit for motor protection according to claim 2, characterized in that: The intervention current output circuit also includes a leakage detection intervention current generation circuit module for providing an AC current for the leakage detection active intervention current line. The leakage detection intervention current generation circuit module includes transistors Q1, Q2, and Q3. The positive terminal of the phototransistor of the photocoupler U13 is connected to the base of the transistor Q3 through a resistor R41. The collector of the transistor Q3 is respectively connected to the collector of the transistor Q1 and the base of the transistor Q2 through a resistor R38. The emitter of the transistor Q1 is connected to the positive electrode of the DC power supply V2. The emitter of transistor Q2 is connected to the base of transistor Q1; a resistor R43 is connected between the base and emitter of the transistor Q3, a resistor R31 is connected between the emitter and collector of the transistor Q1, and a resistor R6 is connected between the emitter and base of the transistor Q1; the collector of the transistor Q2 is connected to the input / output interface IO+ on the intelligent motor protector, and the connecting end of the emitter of the transistor Q3 and the resistor R43 is connected to the input / output interface IO- on the intelligent motor protector through a resistor R45.

5. A leakage detection circuit for motor protection according to claim 4, characterized in that: The intervention current output circuit also includes an isolated power supply circuit module for providing a DC power supply V2 for the optical coupling isolation signal output circuit module and the leakage detection intervention current generation circuit module; the isolated power supply circuit module includes a push-pull control chip IC1, a transformer T1 and a dummy load R36, the power input terminal VIN of the push-pull control chip IC1 is connected to the positive electrode of the DC power supply and grounded through a capacitor C3, the center tap of the primary winding of the transformer T1 is connected to the positive electrode of the DC power supply, the two ends of the primary winding of the transformer T1 are respectively connected to the push-pull output terminals VD1 and VD2 of the push-pull control chip IC1, the secondary winding of the transformer T1 is respectively connected to one end of the dummy load R36 through diodes D1 and D2, the center tap of the secondary winding of the transformer T1 is connected to the other end of the dummy load R36, and a capacitor C1 is connected in parallel between the two ends of the dummy load.

6. A leakage detection circuit for motor protection according to claim 2, characterized in that: A leakage detection conversion circuit is also connected between the leakage signal detection port COM3 and the leakage signal detection port IL* of the intelligent motor protector and the ADC interface of the single-chip computer. The leakage detection conversion circuit includes a leakage signal conversion circuit module for converting the secondary side leakage current measured by the leakage current transformer into a voltage signal IL and a leakage signal amplification processing circuit module for amplifying and processing the voltage signal IL. The leakage signal conversion circuit module includes an inductor L7, an inductor L6, a resistor R14 and a capacitor C25. One end of the inductor L7 is connected to the leakage signal detection port COM3, one end of the inductor L6 is connected to the leakage signal detection port IL*, one end of the inductor L7 connected to the leakage signal detection port IL* is also connected to the ground terminal GND through the capacitor C25, the other end of the inductor L6 is connected in parallel with the other end of the inductor L6 through the resistor R14 to form a parallel terminal, and a reference voltage VARF2 is loaded on the parallel terminal, and the voltage signal IL is generated at the connection portion between the inductor L6 and the resistor R14.

7. A leakage detection circuit for motor protection according to claim 6, characterized in that: The leakage signal amplification processing circuit module includes an operational amplifier ICD3, resistors R8, R7, R5, a capacitor C11, a clamping diode D2, and a capacitor C7. The positive input pin of the operational amplifier ICD3 is loaded with a reference voltage VARF2. The negative input pin of the operational amplifier ICD3 is connected to the connection between the inductor L6 and the resistor R14 in the leakage signal conversion circuit module through the resistor R8. A resistor R7 is also connected between the negative input pin and the output pin of the operational amplifier ICD3. The output pin of the operational amplifier ICD3 is connected to the clamping diode D2 through the resistor R5. One end of the operational amplifier ICD3 is loaded with a positive voltage and the other end is grounded. The connection end of the resistor R5 and the clamping diode D2 is also connected to the ground end through the capacitor C7. The amplification processing voltage ILP is formed at the connection end of the resistor R5 and the clamping diode D2.

8. A leakage detection circuit for motor protection according to claim 7, characterized in that: The leakage detection conversion circuit also includes a reference voltage generating circuit module, which includes an operational amplifier IC1A, a capacitor C1, a capacitor C2, a resistor R1, and a resistor array RR1 composed of a number of resistors. The positive power supply terminal of the operational amplifier IC1A is loaded with a positive voltage and is connected to the ground terminal through the capacitor C1, the negative power supply terminal of the operational amplifier IC1A is connected to the ground terminal, the positive input pin of the operational amplifier IC1A is loaded with a positive voltage through the array RR1, the output pin of the operational amplifier IC1A is connected to the ground terminal through the resistor R1 and the capacitor C2, the connection between the resistor R1 and the capacitor C2 is connected to the negative input pin of the operational amplifier IC1A and the reference voltage VARF2 is formed at the connection between the resistor R1 and the capacitor C2.

9. A leakage detection circuit for motor protection according to claim 7, characterized in that: The amplified processing voltage ILP=IL*(1+R7 / R8) formed by the connection end of the resistor R5 and the clamping diode D2.

10. A leakage detection circuit for motor protection according to claim 7, characterized in that: The connection end of the resistor R5 and the clamping diode D2 is connected to the ADC interface of the single chip microcomputer.

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