Benefit and environmental protection are the eternal pursuit of customers. The injection molding machine equipped with a special inverter for injection molding machine not only reduces the impact of the start and stop of the motor on the power grid, but also reduces the pollution of the power supply and plays an environmentally friendly role. At the same time, it can also be installed with a special inverter for injection molding machines. Improve work efficiency and save results. This is undoubtedly a very good selling point for manufacturers. Due to the special nature of the injection molding machine process, various faults will be encountered in the process of installing the special-purpose inverter of the injection molding machine. The following are the problems and treatment methods often encountered in the process of installing the injection molding machine.
Case 1 - Fault Information: Injection Molding Machine Clamping Crash
(1) Case introduction: Zhuhai a plastic electronics Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Haitian machinery 250t quantitative pump; motor power: 22kw; rated current: 42a; injection products: speaker bracket.
(2) Fault phenomenon: After the inverter is installed and debugged, the startup motor will not lock and die, and the inverter operation panel does not display fault information. The on-site technician also reported that the inverter had set the maximum frequency of 50hz when the injection molding machine was locked, but it could not lock the mold, and the injection molding machine was normally locked under the power frequency operation.
(3) Failure analysis: Listen to the manufacturer technician at the scene to explain: “The product molded by the injection molding machine is a high-power horn bracket. The proportional pressure set during molding is much higher than that of the general mold. After one or two locks can not be molded." After listening to the technician's words, it can be seen that the troubleshooting is not in the injection molding machine itself, you can start from the inverter side, take the multimeter to measure the inverter input voltage of about 350v, the output voltage is only about 360v, you can confirm that The plant's grid voltage is low and the fault is caused.
Some people may think, how can the frequency conversion run to 50hz frequency can not open the model? How can the power frequency 50hz frequency be opened? After field measurement, under the condition of load and working conditions, the power frequency 50hz power supply is used. With the variable frequency 50hz power supply to the motor, the power consumed is different. After using the same 50hz frequency after frequency conversion, the power provided is less than the power provided by the power frequency power supply (about less than 10%), so the above failure phenomenon will occur. The conclusion of practice.
(4) Troubleshooting: For the above fault information, we should think of the two parameters "maximum output voltage and maximum output frequency" in the inverter, and raise any of these two parameters to a reasonable value, such as the maximum The output voltage is modified from 380v to 400v or the maximum output frequency is changed from 50hz to 55hz, which can solve this mode-locking problem. Because the input voltage can not be changed, we can ensure the normal operation of the device by increasing the output frequency and output voltage of the inverter. Remember to set the two parameters too large, to ensure that the equipment is running normally, and setting the assembly is not good for the motor.
Case 2 - Fault Information: The inverter occasionally reports "analog input abnormal fault"
(1) Case introduction: Shenzhen Electric Industrial Co., Ltd. injection molding machine frequency conversion energy-saving transformation project. Equipment name: Donghua Machinery 150t quantitative pump; motor power: 15kw; rated current: 29.6a; injection products: pacifier.
(2) Fault phenomenon: The user reports: “The inverter is installed and running for a period of time is very stable. Because the production needs to replace another set of molds, the inverter will report “analog input abnormal fault†and stop after working for a period of time. After pressing the inverter fault reset button, it can run normally. After a period of time, it will report the same fault and convert the inverter to the power frequency to run normally.
(3) Fault analysis: According to the experience, the inverter reports analog input error. Generally, there are three types of faults: the analog input signal is disturbed; the analog input circuit is abnormal; the analog input voltage/current is too high.
The on-site observation of the process parameters of the injection molding machine is within the allowable range, and the modification of the inverter parameters has not improved. Since the inverter has done anti-jamming treatment to temporarily eliminate the first cause of the fault, the inverter can normally receive the analog signal and eliminate the second cause of the fault. Finally, the third cause of the fault is left, and the specific pressure of the injection molding machine is The specific flow feedback signal is a current signal of 0~1a. The multimeter is converted to the current range to measure the proportional flow rate and the proportional pressure signal of the injection molding machine. The measurement result shows that the current of the injection molding machine reaches about 1.2a during high voltage clamping and injection, which exceeds the frequency conversion. The current check range of the control card of the injection molding machine will not report the abnormal input of the analog input. The main reason is that the injection molding machine has been used for more than ten years, and the control system on the equipment has been aging, resulting in large variations in the error between the set parameters and the actual parameters.
(4) Troubleshooting: The injection molding machine control card on the inverter can select the current input range 0~2a and 0~1a through the jumper. Insert the shorting block into the 0~2a current file and re-modify the inverter parameters.
(5) Fault countermeasures: For this fault problem, some users are advised to use the dual-channel signal isolation injection molding machine controller when selecting the inverter, because the anti-interference is strong; it is required to provide 2 independent 0~10v, 0 ~24v, 0~2a, 0~1a input terminals, convenient to take various feedback signals on the injection molding machine.
(6) Case 3 - Fault information: leakage circuit breaker tripping
(1) Case Description: Shenzhen Plastic Hardware Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Bochuang Machinery 280t quantitative pump; motor power: 30kw; rated current: 58a; injection products: charger shell.
(2) Fault phenomenon: After the inverter is put into normal operation, the leakage circuit breaker of the main circuit control cabinet of the injection molding machine trips. The equipment operates normally when no motor is running at no load; however, after the motor is connected, the leakage circuit breaker trips in an instant.
(3) Fault analysis: Open the main circuit control cabinet of the injection molding machine and find that the user replaces the circuit breaker of the main power switch with the leakage circuit breaker. Why is the leakage circuit breaker easy to trip when using the inverter? The reason is that the output voltage in the inverter runs with higher harmonic components, which causes parasitic capacitance between the motor winding and the casing, and between the conductor and the ground. The parasitic capacitance forms a leakage current path through the wire and the ground, the casing and the ground, as shown in Figure 1. The leakage current on the output side of the inverter is about three times that of the power frequency operation, plus the leakage current of the motor, when this leakage current When the setting current value is greater than the leakage circuit breaker, the earth leakage circuit breaker will trip.
(4) Troubleshooting: When encountering the above faults, the following methods and countermeasures should be taken, and the fault can be effectively eliminated:
Using an earth leakage circuit breaker designed for high harmonic/surge leakage current, the operating current of the earth leakage circuit breaker should be greater than 5 times the leakage current during power frequency operation;
The leakage circuit breaker shall be located on the input side of the frequency converter, and it is more suitable after the air is opened;
Take the method of reducing the carrier frequency of the inverter to reduce the influence of ground leakage current caused by parasitic capacitance;
The leakage current is isolated by adding an isolation transformer on the input side of the inverter;
If necessary, it is best to add a reactor to the input/output of the inverter to suppress it, which is nothing more than increasing the cost.
(7) Case 4 - Fault Information: Interfering with the temperature of the heating system
(1) Case introduction: Zhuhai Electric Appliance Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Huada Machinery 190t quantitative pump; motor power: 18.5kw; rated current: 36a; injection products: mirror for touch screen.
(2) Fault phenomenon: After the inverter is put into use, it interferes with the heating system of the injection molding machine, so that the injection molding machine system can not operate normally. The actual temperature and the set temperature of several temperature zones on the injection molding machine have several tens of degrees or even the error of Baidu. Change (normal error is 0 to 8 ° C).
(3) Fault analysis: The problem often encountered in the frequency conversion energy-saving transformation of injection molding machine is that the interference injection molding machine can not operate normally after the transformation. The heating system of the injection molding machine generally uses the thermocouple to detect the temperature. This detection component is easily affected by the high-order harmonic interference of the inverter output. , resulting in inaccurate temperature display and control of the injection molding machine.
(4) Troubleshooting: The interference can be suppressed from the following aspects:
Minimize the connection between the inverter and the motor of the injection molding machine, and use a metal hose set for the power line;
Install a magnetic ring on the input side and output side of the inverter to reduce the carrier frequency of the inverter;
The power supply ground of the injection molding machine and the motor housing ground must be reliably connected to the grounding terminal of the inverter;
The internal temperature control galvanic power supply of the injection molding machine is coupled with a RC filter circuit;
The temperature-controlled galvanic power supply line for the injection molding machine heating system is installed in the ring-shaped powerful magnet, and the power supply line is wound on the strong magnet together in the same direction for 3 to 5 turns. This is a more practical and economical solution. Some of the peers may not have seen a strong magnet. Please see Figure 2 below (standard value: outer diameter 25mm, inner diameter 10mm).
(5) Troubleshooting: The first to fourth methods have been tried one by one, and the fault phenomenon has been improved, but the temperature change on the injection molding machine is still too large. When the fifth method is adopted, the fault phenomenon is obviously improved, and the temperature change on the heating system is basically the same as that under the power frequency operation.
People who don't understand seem to be relatively simple. In fact, it is far more than just a technical engineer to understand. In the future inverter transformation, there will definitely be many failure problems. Of course, this is also testing each of us. Resilience and troubleshooting capabilities of a field technician. The above are some of the troubleshooting experiences and experiences encountered in the energy-saving retrofit of injection molding machines that I have provided for you. I hope that the above work can be used for reference in the design and application work of the competitors engaged in frequency conversion energy-saving transformation.
Case 1 - Fault Information: Injection Molding Machine Clamping Crash
(1) Case introduction: Zhuhai a plastic electronics Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Haitian machinery 250t quantitative pump; motor power: 22kw; rated current: 42a; injection products: speaker bracket.
(2) Fault phenomenon: After the inverter is installed and debugged, the startup motor will not lock and die, and the inverter operation panel does not display fault information. The on-site technician also reported that the inverter had set the maximum frequency of 50hz when the injection molding machine was locked, but it could not lock the mold, and the injection molding machine was normally locked under the power frequency operation.
(3) Failure analysis: Listen to the manufacturer technician at the scene to explain: “The product molded by the injection molding machine is a high-power horn bracket. The proportional pressure set during molding is much higher than that of the general mold. After one or two locks can not be molded." After listening to the technician's words, it can be seen that the troubleshooting is not in the injection molding machine itself, you can start from the inverter side, take the multimeter to measure the inverter input voltage of about 350v, the output voltage is only about 360v, you can confirm that The plant's grid voltage is low and the fault is caused.
Some people may think, how can the frequency conversion run to 50hz frequency can not open the model? How can the power frequency 50hz frequency be opened? After field measurement, under the condition of load and working conditions, the power frequency 50hz power supply is used. With the variable frequency 50hz power supply to the motor, the power consumed is different. After using the same 50hz frequency after frequency conversion, the power provided is less than the power provided by the power frequency power supply (about less than 10%), so the above failure phenomenon will occur. The conclusion of practice.
(4) Troubleshooting: For the above fault information, we should think of the two parameters "maximum output voltage and maximum output frequency" in the inverter, and raise any of these two parameters to a reasonable value, such as the maximum The output voltage is modified from 380v to 400v or the maximum output frequency is changed from 50hz to 55hz, which can solve this mode-locking problem. Because the input voltage can not be changed, we can ensure the normal operation of the device by increasing the output frequency and output voltage of the inverter. Remember to set the two parameters too large, to ensure that the equipment is running normally, and setting the assembly is not good for the motor.
Case 2 - Fault Information: The inverter occasionally reports "analog input abnormal fault"
(1) Case introduction: Shenzhen Electric Industrial Co., Ltd. injection molding machine frequency conversion energy-saving transformation project. Equipment name: Donghua Machinery 150t quantitative pump; motor power: 15kw; rated current: 29.6a; injection products: pacifier.
(2) Fault phenomenon: The user reports: “The inverter is installed and running for a period of time is very stable. Because the production needs to replace another set of molds, the inverter will report “analog input abnormal fault†and stop after working for a period of time. After pressing the inverter fault reset button, it can run normally. After a period of time, it will report the same fault and convert the inverter to the power frequency to run normally.
(3) Fault analysis: According to the experience, the inverter reports analog input error. Generally, there are three types of faults: the analog input signal is disturbed; the analog input circuit is abnormal; the analog input voltage/current is too high.
The on-site observation of the process parameters of the injection molding machine is within the allowable range, and the modification of the inverter parameters has not improved. Since the inverter has done anti-jamming treatment to temporarily eliminate the first cause of the fault, the inverter can normally receive the analog signal and eliminate the second cause of the fault. Finally, the third cause of the fault is left, and the specific pressure of the injection molding machine is The specific flow feedback signal is a current signal of 0~1a. The multimeter is converted to the current range to measure the proportional flow rate and the proportional pressure signal of the injection molding machine. The measurement result shows that the current of the injection molding machine reaches about 1.2a during high voltage clamping and injection, which exceeds the frequency conversion. The current check range of the control card of the injection molding machine will not report the abnormal input of the analog input. The main reason is that the injection molding machine has been used for more than ten years, and the control system on the equipment has been aging, resulting in large variations in the error between the set parameters and the actual parameters.
(4) Troubleshooting: The injection molding machine control card on the inverter can select the current input range 0~2a and 0~1a through the jumper. Insert the shorting block into the 0~2a current file and re-modify the inverter parameters.
(5) Fault countermeasures: For this fault problem, some users are advised to use the dual-channel signal isolation injection molding machine controller when selecting the inverter, because the anti-interference is strong; it is required to provide 2 independent 0~10v, 0 ~24v, 0~2a, 0~1a input terminals, convenient to take various feedback signals on the injection molding machine.
(6) Case 3 - Fault information: leakage circuit breaker tripping
(1) Case Description: Shenzhen Plastic Hardware Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Bochuang Machinery 280t quantitative pump; motor power: 30kw; rated current: 58a; injection products: charger shell.
(2) Fault phenomenon: After the inverter is put into normal operation, the leakage circuit breaker of the main circuit control cabinet of the injection molding machine trips. The equipment operates normally when no motor is running at no load; however, after the motor is connected, the leakage circuit breaker trips in an instant.
(3) Fault analysis: Open the main circuit control cabinet of the injection molding machine and find that the user replaces the circuit breaker of the main power switch with the leakage circuit breaker. Why is the leakage circuit breaker easy to trip when using the inverter? The reason is that the output voltage in the inverter runs with higher harmonic components, which causes parasitic capacitance between the motor winding and the casing, and between the conductor and the ground. The parasitic capacitance forms a leakage current path through the wire and the ground, the casing and the ground, as shown in Figure 1. The leakage current on the output side of the inverter is about three times that of the power frequency operation, plus the leakage current of the motor, when this leakage current When the setting current value is greater than the leakage circuit breaker, the earth leakage circuit breaker will trip.
(4) Troubleshooting: When encountering the above faults, the following methods and countermeasures should be taken, and the fault can be effectively eliminated:
Using an earth leakage circuit breaker designed for high harmonic/surge leakage current, the operating current of the earth leakage circuit breaker should be greater than 5 times the leakage current during power frequency operation;
The leakage circuit breaker shall be located on the input side of the frequency converter, and it is more suitable after the air is opened;
Take the method of reducing the carrier frequency of the inverter to reduce the influence of ground leakage current caused by parasitic capacitance;
The leakage current is isolated by adding an isolation transformer on the input side of the inverter;
If necessary, it is best to add a reactor to the input/output of the inverter to suppress it, which is nothing more than increasing the cost.
(7) Case 4 - Fault Information: Interfering with the temperature of the heating system
(1) Case introduction: Zhuhai Electric Appliance Co., Ltd. injection molding machine frequency conversion energy-saving transformation project; equipment name: Huada Machinery 190t quantitative pump; motor power: 18.5kw; rated current: 36a; injection products: mirror for touch screen.
(2) Fault phenomenon: After the inverter is put into use, it interferes with the heating system of the injection molding machine, so that the injection molding machine system can not operate normally. The actual temperature and the set temperature of several temperature zones on the injection molding machine have several tens of degrees or even the error of Baidu. Change (normal error is 0 to 8 ° C).
(3) Fault analysis: The problem often encountered in the frequency conversion energy-saving transformation of injection molding machine is that the interference injection molding machine can not operate normally after the transformation. The heating system of the injection molding machine generally uses the thermocouple to detect the temperature. This detection component is easily affected by the high-order harmonic interference of the inverter output. , resulting in inaccurate temperature display and control of the injection molding machine.
(4) Troubleshooting: The interference can be suppressed from the following aspects:
Minimize the connection between the inverter and the motor of the injection molding machine, and use a metal hose set for the power line;
Install a magnetic ring on the input side and output side of the inverter to reduce the carrier frequency of the inverter;
The power supply ground of the injection molding machine and the motor housing ground must be reliably connected to the grounding terminal of the inverter;
The internal temperature control galvanic power supply of the injection molding machine is coupled with a RC filter circuit;
The temperature-controlled galvanic power supply line for the injection molding machine heating system is installed in the ring-shaped powerful magnet, and the power supply line is wound on the strong magnet together in the same direction for 3 to 5 turns. This is a more practical and economical solution. Some of the peers may not have seen a strong magnet. Please see Figure 2 below (standard value: outer diameter 25mm, inner diameter 10mm).
(5) Troubleshooting: The first to fourth methods have been tried one by one, and the fault phenomenon has been improved, but the temperature change on the injection molding machine is still too large. When the fifth method is adopted, the fault phenomenon is obviously improved, and the temperature change on the heating system is basically the same as that under the power frequency operation.
People who don't understand seem to be relatively simple. In fact, it is far more than just a technical engineer to understand. In the future inverter transformation, there will definitely be many failure problems. Of course, this is also testing each of us. Resilience and troubleshooting capabilities of a field technician. The above are some of the troubleshooting experiences and experiences encountered in the energy-saving retrofit of injection molding machines that I have provided for you. I hope that the above work can be used for reference in the design and application work of the competitors engaged in frequency conversion energy-saving transformation.
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