Protection device for monitoring partial discharge of low-voltage motor

Abstract

A protection device for monitoring partial discharge of a low-voltage motor belongs to the technical field of circuit monitoring and is used for solving the problem that a conventional low-voltage motor protection device cannot judge and discriminate partial discharge signals of the low-voltage motor. Comprising a motor starting unit and a motor control unit. The motor starting unit comprises a 380V alternating current power supply, a three-phase circuit breaker Q1, a motor contactor normally open contact, an A-phase current sensor T1, a B-phase current sensor T2, a C-phase current sensor T3, a zero line current sensor T4 and a three-phase alternating current asynchronous motor M1; the 380V alternating current power supply and the three-phase alternating current asynchronous motor M1 both adopt a three-phase four-wire system; according to the utility model, the current condition of each phase of the low-voltage motor is monitored through the plurality of current sensors arranged on the motor starting unit, and whether a three-phase current imbalance fault or a motor partial discharge fault occurs in the motor is analyzed according to the current signal change.

Description

Technical Field

[0001] This utility model belongs to the field of circuit monitoring technology and relates to a protection device for monitoring partial discharge of low-voltage motors. Background Technology

[0002] Low-voltage motors are motors with operating voltages of 380V, 220V, or lower, and a rated voltage not exceeding 1000V. They are widely used in household, commercial, and industrial production. Low-voltage motors have limited and relatively simple protection functions. Existing technologies mostly use thermal relays or integrated motor protectors, whose protective components themselves have low accuracy and poor reliability, easily leading to motor protection failure or protection device malfunction, resulting in motor damage. More importantly, existing thermal relays and integrated motor protectors cannot identify or distinguish partial discharge signals in low-voltage motors, causing them to operate with defects for extended periods and eventually fail. Utility Model Content

[0003] The technical solution of this utility model is used to solve the problem that existing low-voltage motor protection devices cannot judge and identify the partial discharge signal of low-voltage motors, resulting in the long-term operation of low-voltage motors with defects and damage.

[0004] This utility model solves the above-mentioned technical problems through the following technical solution:

[0005] A protection device for monitoring partial discharge of a low-voltage motor includes a motor starting unit and a motor control unit; the motor starting unit includes a 380V AC power supply, a three-phase circuit breaker Q1, normally open contacts of a motor contactor, an A-phase current sensor T1, a B-phase current sensor T2, a C-phase current sensor T3, a neutral wire current sensor T4, and a three-phase AC asynchronous motor M1; both the 380V AC power supply and the three-phase AC asynchronous motor M1 adopt a three-phase four-wire system.

[0006] The A-phase, B-phase, and C-phase input lines of the 380V AC power supply are respectively connected to the three input terminals of the three-phase circuit breaker Q1. The three output terminals of the three-phase circuit breaker Q1 are respectively connected to the three input terminals of the normally open contacts of the motor contactor. The three output terminals of the normally open contacts of the motor contactor are respectively connected to the input terminals of the A-phase current sensor T1, the B-phase current sensor T2, and the C-phase current sensor T3. The output terminal of the A-phase current sensor T1 is connected to the A-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the B-phase current sensor T2 is connected to the B-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the C-phase current sensor T3 is connected to the C-phase input terminal of the three-phase AC asynchronous motor M1. The neutral wire of the three-phase AC asynchronous motor M1 is grounded. The neutral wire of the 380V AC power supply is connected to the input terminal of the neutral wire current sensor T4, and the output terminal of the neutral wire current sensor T4 is grounded.

[0007] The motor control unit includes a 220V AC power supply, a two-phase circuit breaker Q2, a switching power supply P1, a motor contactor coil, an audible and visual alarm module H1, a PLC, and an analog input module AI. The live wire and neutral wire of the 220V AC power supply are connected to the two input terminals of the two-phase circuit breaker Q2, and the two output terminals of the two-phase circuit breaker Q2 are connected to the two input terminals of the switching power supply P1. The positive terminal of the output terminal of the switching power supply P1 is connected to the positive terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The negative terminal of the output terminal of the switching power supply P1 is connected to the negative terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The PLC and the analog input module AI are connected via a bus communication connection.

[0008] The PLC's Q0.0 port is connected to the input terminal of the motor contactor coil, and the output terminal of the motor contactor coil is connected to the negative terminal of the switching power supply P1; the PLC's Q0.4 port is connected to the input terminal of the audible and visual alarm module H1, and the output terminal of the audible and visual alarm module H1 is connected to the negative terminal of the switching power supply P1.

[0009] The positive terminal of the communication end of phase A current sensor T1 is connected to port PIW264 of analog input module AI, and the negative terminal of the communication end of phase A current sensor T1 is connected to port PIW265 of analog input module AI; the positive terminal of the communication end of phase B current sensor T2 is connected to port PIW266 of analog input module AI, and the negative terminal of the communication end of phase B current sensor T2 is connected to port PIW267 of analog input module AI; the positive terminal of the communication end of phase C current sensor T3 is connected to port PIW268 of analog input module AI, and the negative terminal of the communication end of phase C current sensor T3 is connected to port PIW269 of analog input module AI; the positive terminal of the communication end of neutral wire current sensor T4 is connected to port PIW270 of analog input module AI, and the negative terminal of the communication end of neutral wire current sensor T4 is connected to port PIW271 of analog input module AI.

[0010] Furthermore, the sound and light alarm module H1 is a sound and light alarm, specifically model AD16-22SM, with an operating voltage of ADC24V.

[0011] Furthermore, the A-phase current sensor T1, B-phase current sensor T2, C-phase current sensor T3 and neutral wire current sensor T4 are high-precision current sensors, model AC0-10A, with an operating voltage of 24VDC, an accuracy of 0.2%, and a rated output of 4-20mA.

[0012] Furthermore, the PLC is a Siemens S7-300 series, model 6ES7 313C-2DP; the analog input module AI is an 8-channel analog input module, model 6ES7 331-7KF02.

[0013] Furthermore, the switching power supply P1 is a 24V DC regulated power supply, model PS307, with a rated input voltage of 220VAC, a rated output voltage of 24VDC, and a rated operating current of 2A.

[0014] Furthermore, the motor contactor is model AL9-30, with a rated pull-in voltage of DC24V and a rated operating current of 0-9A.

[0015] The advantages of this utility model are:

[0016] This invention monitors the current status of each phase of a low-voltage motor by installing multiple current sensors on the motor starting unit. The current signal is input to the PLC through an analog input module. Based on the changes in the current signal, the PLC analyzes whether the motor has a three-phase current imbalance fault or a partial discharge fault. The invention provides online monitoring of the low-voltage motor's operating status, quantifies the monitoring and protection data, and accurately judges the partial discharge or current imbalance fault that occurs during motor operation. It can detect faults in the early stages of abnormal motor conditions and stop motor operation, issuing timely warnings to prevent the motor fault from escalating further. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a protection device for monitoring partial discharge of a low-voltage motor according to Embodiment 1 of this utility model. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0019] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments:

[0020] Example 1

[0021] like Figure 1 Specifically, a protection device for monitoring partial discharge of a low-voltage motor is disclosed, comprising a motor starting unit and a motor control unit; the motor starting unit includes a 380V AC power supply, a three-phase circuit breaker Q1, a normally open contact of a motor contactor, an A-phase current sensor T1, a B-phase current sensor T2, a C-phase current sensor T3, a neutral wire current sensor T4, and a three-phase AC asynchronous motor M1; both the 380V AC power supply and the three-phase AC asynchronous motor M1 adopt a three-phase four-wire system;

[0022] The A-phase, B-phase, and C-phase input lines of the 380V AC power supply are respectively connected to the three input terminals of the three-phase circuit breaker Q1. The three output terminals of the three-phase circuit breaker Q1 are respectively connected to the three input terminals of the normally open contacts of the motor contactor. The three output terminals of the normally open contacts of the motor contactor are respectively connected to the input terminals of the A-phase current sensor T1, the B-phase current sensor T2, and the C-phase current sensor T3. The output terminal of the A-phase current sensor T1 is connected to the A-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the B-phase current sensor T2 is connected to the B-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the C-phase current sensor T3 is connected to the C-phase input terminal of the three-phase AC asynchronous motor M1. The neutral wire of the three-phase AC asynchronous motor M1 is grounded. The neutral wire of the 380V AC power supply is connected to the input terminal of the neutral wire current sensor T4, and the output terminal of the neutral wire current sensor T4 is grounded.

[0023] In this embodiment, the motor starting unit is the main circuit. A 380V AC power supply is connected in series with a three-phase circuit breaker Q1, the normally open contact of the motor contactor KM, and multiple current sensors, and then connected to a three-phase AC asynchronous motor M1. The 380V AC power supply adopts a three-phase four-wire system. The three power input lines L1, L2, and L3, along with the neutral wire, are connected to the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral wire current sensor T4, respectively. The normally open contact of the motor contactor KM is located in the motor starting unit. After the three-phase circuit breaker Q1 is closed, the main circuit is connected after the motor control unit is powered on and performs a self-test.

[0024] Specifically, the three-phase circuit breaker Q1 is model DZ47-60 / C40, used to provide three-phase power to low-voltage motors and circuits.

[0025] The motor contactor is model AL9-30, with a rated pull-in voltage of DC24V and a rated operating current of 0-9A, and is used to control the start and stop of a low-voltage motor.

[0026] The motor control unit includes a 220V AC power supply, a two-phase circuit breaker Q2, a switching power supply P1, a motor contactor coil, an audible and visual alarm module H1, a PLC, and an analog input module AI. The live wire and neutral wire of the 220V AC power supply are connected to the two input terminals of the two-phase circuit breaker Q2, and the two output terminals of the two-phase circuit breaker Q2 are connected to the two input terminals of the switching power supply P1. The positive terminal of the output terminal of the switching power supply P1 is connected to the positive terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The negative terminal of the output terminal of the switching power supply P1 is connected to the negative terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The PLC and the analog input module AI are connected via a bus communication connection.

[0027] The Q0.0 port of the PLC is connected to the input terminal of the motor contactor coil, and the output terminal of the motor contactor coil is connected to the negative terminal of the output of the switching power supply P1.

[0028] The Q0.4 port of the PLC is connected to the input terminal of the audible and visual alarm module H1, and the output terminal of the audible and visual alarm module H1 is connected to the negative terminal of the output terminal of the switching power supply P1.

[0029] Specifically, the PLC is a Siemens S7-300 series, specifically model 6ES7 313C-2DP, used to read the output signal of the current sensor, calculate the operating current of the low-voltage motor, logically determine whether the low-voltage motor is operating normally, issue an alarm signal, and control the start and stop of the motor.

[0030] The analog input module AI is an 8-channel analog input module, specifically model 6ES7 331-7KF02, used to receive analog signals output by current sensors, convert them into data that can be processed by the programmable logic controller (PLC), and input them into the PLC.

[0031] The switching power supply P1 is a 24V DC regulated power supply, model PS307, with a rated input voltage of 220VAC, a rated output voltage of 24VDC, and a rated operating current of 2A, used to provide operating power for the PLC and current sensor.

[0032] The positive terminal of the communication terminal of the A-phase current sensor T1 is connected to the PIW264 port of the analog input module AI, and the negative terminal of the communication terminal of the A-phase current sensor T1 is connected to the PIW265 port of the analog input module AI.

[0033] The positive terminal of the B-phase current sensor T2 is connected to the PIW266 port of the analog input module AI, and the negative terminal of the B-phase current sensor T2 is connected to the PIW267 port of the analog input module AI.

[0034] The positive terminal of the C-phase current sensor T3 is connected to the PIW268 port of the analog input module AI, and the negative terminal of the C-phase current sensor T3 is connected to the PIW269 port of the analog input module AI.

[0035] The positive terminal of the neutral current sensor T4 is connected to the PIW270 port of the analog input module AI, and the negative terminal of the neutral current sensor T4 is connected to the PIW271 port of the analog input module AI.

[0036] Specifically, the A-phase current sensor T1, B-phase current sensor T2, C-phase current sensor T3 and neutral wire current sensor T4 are high-precision current sensors, model AC0-10A, with an operating voltage of 24VDC, an accuracy of 0.2%, and a rated output of 4-20mA.

[0037] Furthermore, the audible and visual alarm module H1 is an audible and visual alarm device, specifically model AD16-22SM, with an operating voltage of ADC24V, used to issue audible and visual alarm signals when a low-voltage motor fails.

[0038] In this embodiment, the motor control unit is a control circuit. A 220V AC power supply provides operating voltage to the PLC, analog input module, motor contactor KM coil, and multiple current sensors via a switching power supply P1. When the two-phase circuit breaker Q2 is closed, and the low-voltage motor needs to be started, the PLC sends a high-level signal through port Q0.0, energizing the motor contactor KM coil. Both the motor starting unit and the motor control unit are then connected and enter the working state. Meanwhile, multiple current sensors also send the current signals of their respective phase lines to the PLC through the analog input module AI. By comparing the fluctuations in the current signals from the current sensors, the PLC analyzes whether partial discharge or three-phase current imbalance faults occur during motor operation. If a fault is found, the PLC sends a high-level signal to the audible and visual alarm module H1 through port Q0.4, triggering an alarm sound and visual indication.

[0039] Furthermore, the I0.1 terminal of the PLC is used to detect the closing feedback signal of the motor contactor. When the I0.1 terminal is high and the average current of the motor is greater than 1A, the motor operation is monitored for a delay of 10 seconds.

[0040] The PLC's I0.0 terminal is a reset signal input. When I0.0 is 1, the motor resets and restarts. If a fault occurs and a reset operation is not performed, the motor cannot be restarted.

[0041] Working principle:

[0042] (1) Power supply stage of the device:

[0043] The motor starting unit is the main circuit. A 380V AC power supply is connected in series with a three-phase circuit breaker Q1, the normally open contact of the motor contactor KM, and multiple current sensors, before being connected to a three-phase AC asynchronous motor M1. The normally open contact of the motor contactor KM is located in the motor starting unit. After the three-phase circuit breaker Q1 is closed, the motor control unit needs to be powered on and complete its self-test before the normally open contact of the motor contactor closes, and the main circuit is connected.

[0044] The motor control unit is a control circuit. A 220V AC power supply is converted to 24V DC via a switching power supply P1, providing operating voltage for the PLC, analog input module AI, motor contactor KM, A-phase current sensor T1, B-phase current sensor T2, C-phase current sensor T3, and neutral current sensor T4. When the two-phase circuit breaker Q2 closes, the PLC sends a 24V high-level signal to the motor contactor coil through port Q0.0. The motor contactor coil is energized, the normally open contacts of the motor contactor close, and both the motor starting unit and the motor control unit are activated and enter the working state.

[0045] (2) Device monitoring stage:

[0046] The 380V AC power supply uses a three-phase four-wire system. Since phase A power input line L1, phase B power input line L2, phase C power input line L3, and the neutral wire are respectively connected to phase A current sensor T1, phase B current sensor T2, phase C current sensor T3, and neutral wire current sensor T4, these current sensors can send the current signal of their respective phase lines to the motor control unit. For example... Figure 1 As shown, the four current sensors will output a 4-20mA current signal I1, I2, I3, and I4 respectively, which correspond to the current in the A-phase winding, B-phase winding, C-phase winding, and neutral line of the low-voltage motor, and are sent to the PLC through the 8-channel analog input module AI.

[0047] Specifically, ports PIW264 and PIW265 are used to detect the A-phase current value I1 of the low-voltage motor, ports PIW266 and PIW267 are used to detect the B-phase current value I2 of the low-voltage motor, and ports PIW268 and PIW269 are used to detect the C-phase current value I3 of the low-voltage motor. When the low-voltage motor is operating normally, the currents in its three-phase windings should be basically balanced, satisfying I1-I2≈0, I2-I3≈0, and I3-I1≈0. If these conditions are not met, the three-phase currents are detected separately: the difference between any two phases of the three-phase current is calculated. If the difference is greater than 1.5A, a three-phase current imbalance fault is identified, and the system reports a three-phase current imbalance fault after a 0.5S delay. When the single-phase current value is greater than 7.5A, the system reports a partial discharge fault of the motor after a 0.2S delay.

[0048] When a three-phase current imbalance fault or a motor partial discharge fault is detected, the PLC outputs a low level at the Q0.0 terminal, the motor contactor coil is de-energized, the normally open contact of the motor contactor opens, and the motor starting unit is de-energized; at the same time, the PLC's Q0.4 terminal sends a high-level signal to the audible and visual alarm module H1 through the Q0.4 port, and the audible and visual alarm emits an alarm sound and light indication.

[0049] The PIW270 and PIW271 ports are used to detect whether there is a current I4 on the neutral line of the low-voltage motor. When the motor windings are damp, aged, or other reasons that cause weak points in the winding insulation to discharge to ground (partial discharge), a current signal will be induced in the neutral line current transformer T4. When the I4 current value is greater than 200mA and the duration is greater than 0.2s, the system will report a partial discharge fault in the motor.

[0050] This invention monitors the current status of each phase of a low-voltage motor by installing multiple current sensors on the motor starting unit. The current signal is input to the PLC through an analog input module. Based on the changes in the current signal, the PLC analyzes whether the motor has a three-phase current imbalance fault or a partial discharge fault. The invention provides online monitoring of the low-voltage motor's operating status, quantifies the monitoring and protection data, and accurately judges the partial discharge or current imbalance fault that occurs during motor operation. It can detect faults in the early stages of abnormal motor conditions and stop motor operation, issuing timely warnings to prevent the motor fault from escalating further.

[0051] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A protection device for monitoring partial discharge of a low-voltage motor, characterized in that, It includes a motor starting unit and a motor control unit; the motor starting unit includes a 380V AC power supply, a three-phase circuit breaker Q1, a normally open contact of a motor contactor, an A-phase current sensor T1, a B-phase current sensor T2, a C-phase current sensor T3, a neutral wire current sensor T4, and a three-phase AC asynchronous motor M1; both the 380V AC power supply and the three-phase AC asynchronous motor M1 adopt a three-phase four-wire system; The A-phase, B-phase, and C-phase input lines of the 380V AC power supply are respectively connected to the three input terminals of the three-phase circuit breaker Q1. The three output terminals of the three-phase circuit breaker Q1 are respectively connected to the three input terminals of the normally open contacts of the motor contactor. The three output terminals of the normally open contacts of the motor contactor are respectively connected to the input terminals of the A-phase current sensor T1, the B-phase current sensor T2, and the C-phase current sensor T3. The output terminal of the A-phase current sensor T1 is connected to the A-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the B-phase current sensor T2 is connected to the B-phase input terminal of the three-phase AC asynchronous motor M1. The output terminal of the C-phase current sensor T3 is connected to the C-phase input terminal of the three-phase AC asynchronous motor M1. The neutral wire of the three-phase AC asynchronous motor M1 is grounded. The neutral wire of the 380V AC power supply is connected to the input terminal of the neutral wire current sensor T4, and the output terminal of the neutral wire current sensor T4 is grounded. The motor control unit includes a 220V AC power supply, a two-phase circuit breaker Q2, a switching power supply P1, a motor contactor coil, an audible and visual alarm module H1, a PLC, and an analog input module AI. The live wire and neutral wire of the 220V AC power supply are connected to the two input terminals of the two-phase circuit breaker Q2, and the two output terminals of the two-phase circuit breaker Q2 are connected to the two input terminals of the switching power supply P1. The positive terminal of the output terminal of the switching power supply P1 is connected to the positive terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The negative terminal of the output terminal of the switching power supply P1 is connected to the negative terminals of the power supply of the analog input module AI, the PLC, the A-phase current sensor T1, the B-phase current sensor T2, the C-phase current sensor T3, and the neutral current sensor T4, respectively. The PLC and the analog input module AI are connected via a bus communication connection. The PLC's Q0.0 port is connected to the input terminal of the motor contactor coil, and the output terminal of the motor contactor coil is connected to the negative terminal of the switching power supply P1; the PLC's Q0.4 port is connected to the input terminal of the audible and visual alarm module H1, and the output terminal of the audible and visual alarm module H1 is connected to the negative terminal of the switching power supply P1. The positive terminal of the communication end of phase A current sensor T1 is connected to port PIW264 of analog input module AI, and the negative terminal of the communication end of phase A current sensor T1 is connected to port PIW265 of analog input module AI; the positive terminal of the communication end of phase B current sensor T2 is connected to port PIW266 of analog input module AI, and the negative terminal of the communication end of phase B current sensor T2 is connected to port PIW267 of analog input module AI; the positive terminal of the communication end of phase C current sensor T3 is connected to port PIW268 of analog input module AI, and the negative terminal of the communication end of phase C current sensor T3 is connected to port PIW269 of analog input module AI; the positive terminal of the communication end of neutral wire current sensor T4 is connected to port PIW270 of analog input module AI, and the negative terminal of the communication end of neutral wire current sensor T4 is connected to port PIW271 of analog input module AI.

2. The protection device for monitoring partial discharge of a low-voltage motor according to claim 1, characterized in that, The sound and light alarm module H1 is a sound and light alarm, specifically model AD16-22SM, with an operating voltage of ADC24V.

3. The protection device for monitoring partial discharge of a low-voltage motor according to claim 1, characterized in that, The phase A current sensor T1, phase B current sensor T2, phase C current sensor T3, and neutral wire current sensor T4 are high-precision current sensors, model AC0-10A, with an operating voltage of 24VDC, an accuracy of 0.2%, and a rated output of 4-20mA.

4. The protection device for monitoring partial discharge of a low-voltage motor according to claim 1, characterized in that, The PLC is a Siemens S7-300 series, model 6ES7 313C-2DP; the analog input module AI is an 8-channel analog input module, model 6ES7 331-7KF02.

5. A protection device for monitoring partial discharge of a low-voltage motor according to claim 1, characterized in that, The switching power supply P1 is a 24V DC regulated power supply, model PS307, with a rated input voltage of 220VAC, a rated output voltage of 24VDC, and a rated operating current of 2A.

6. The protection device for monitoring partial discharge of a low-voltage motor according to claim 1, characterized in that, The motor contactor is model AL9-30, with a rated pull-in voltage of DC24V and a rated operating current of 0-9A.

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