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Common failure causes and preventive measures of inverters for packing equipment
Edit:Qingdao Mountain Plastic extruding Equipment Co., Ltd.   PublicDate:2017-11-20

The inverter of packing equipment is composed of main circuit, power circuit, IPM drive and protection circuit, cooling fan and other parts. Its structure is mostly unitized or modularized. If the usage method is incorrect or the setting environment is unreasonable, it will easily cause misoperation and failure of the mechanical inverter of the packing belt, or it will not meet the expected operating results. To prevent problems before they occur, it is important to carefully analyze the cause of the failure in advance.

First, the self-diagnosis and prevention function of the inverter of the strapping equipment:

1. Older transistor inverters mainly have the following disadvantages: easy to trip, not easy to restart, and low overload capacity. Due to the rapid development of IGBT and CPU, perfect self-diagnosis and fault prevention functions have been added inside the inverter, which has greatly improved the reliability of the inverter.

2. If you use the "Automatic Torque Compensation Function in All Fields" in the vector control inverter, the failure causes such as "insufficient starting torque" and "decreasing output due to changes in environmental conditions" will be well overcome. This function uses the high-speed calculation of the microcomputer inside the inverter to calculate the torque required at the current moment, and quickly corrects and compensates the output voltage to offset the change in inverter output torque caused by changes in external conditions.

3. In addition, because the software development of the inverter is more complete, various fault prevention measures can be set in the inverter in advance, and the fault can still be continued after the fault is resolved. For example, the motor during the free stop process can be re-used. Automatically reset internal faults at startup and maintain continuous operation. When the load torque is too large, the operating curve can be adjusted automatically, and abnormal torque of the mechanical system can be detected. www.yazhijiang.cn.

Analysis of common faults in the main circuit of the inverter of packing belt equipment:

The main circuit is mainly composed of three-phase or single-phase rectifier bridge, smoothing capacitor, filter capacitor, IPM inverter bridge, current limiting resistor, contactor and other components. Many of these common faults are caused by electrolytic capacitors. The life of the electrolytic capacitor is mainly determined by the DC voltage and the internal temperature applied across it. The capacitor type has been selected during the circuit design, so the internal temperature plays a decisive role in the life of the electrolytic capacitor. Electrolytic capacitors will directly affect the service life of the inverter. Generally, the service life is halved for every 10 ° C increase in temperature. Therefore, on the one hand, the appropriate ambient temperature must be considered during installation, and on the other hand, measures can be taken to reduce the pulsating current. The use of AC or DC reactors with improved power factor can reduce the pulsating current and thus extend the life of the electrolytic capacitors. In capacitor maintenance, it is usually easy to measure the electrostatic capacity to determine the deterioration of the electrolytic capacitor. When the electrostatic capacity is less than 80% of the rated value and the insulation resistance is less than 5MΩ, consideration should be given to replacing the electrolytic capacitor.

Third, the typical failure analysis of the main circuit of the inverter of the packing belt equipment:

Symptom: An overcurrent trip occurs during the acceleration, deceleration, or normal operation of a mechanical inverter with a strap. First, it should be distinguished whether it is caused by the load or the frequency converter. If it is a fault of the inverter, you can query the current at the time of trip through historical records, which exceeds the rated current of the inverter or the set value of the electronic thermal relay, and the three-phase voltage and current are balanced. You should consider whether there is an overload. Or sudden changes, such as motor stall. When the load inertia is large, the acceleration time can be appropriately extended. This process does not damage the inverter itself. If the current during tripping is within the rated current of the inverter or within the setting range of the electronic thermal relay, it can be judged that the IPM module or related parts have failed. First, you can determine whether the IPM module is damaged by measuring the forward and reverse resistance between the output terminals U, V, and W of the main circuit of the inverter and the P and N terminals on the DC side. If the module is not damaged, the drive circuit is faulty. If the IPM module is over-current or the inverter is short-circuited to ground during deceleration, it is generally caused by the fault of the upper half-bridge module of the inverter or its drive circuit, and the over-current of the IPM module during acceleration. Part of the fault, the reason for these faults is mostly caused by external dust entering the inverter or the environment is humid. Imported pump valve industrial washing machine

Fourth, the failure analysis of the inverter control loop of packing equipment:

1. The control circuit affects the life of the inverter is the power supply part, which is the smoothing capacitor and the buffer capacitor in the IPM circuit board. The principle is the same as the above, but the pulsating current passing through the capacitor is basically not affected by the main circuit load. Fixed value, so its life is mainly determined by temperature and power-on time. Since the capacitors are soldered to the circuit board, it is difficult to judge the deterioration by measuring the electrostatic capacity. Generally, the capacitor's ambient temperature and service time are used to estimate whether it is close to its service life.

2. The power supply circuit board provides power for the control circuit, IPM drive circuit, surface operation display board, and fans. These power supplies are generally obtained from the DC voltage output from the main circuit and then rectified by the switching power supply. Therefore, in addition to the damage of the rectifier circuit of this circuit, the power of other parts may be affected by a short circuit of the power supply. For example, the control power supply is shorted to the common ground due to misoperation, which causes the switching power supply part on the power circuit board to be damaged. A short circuit in the power supply caused other power supplies to lose power. It is usually easier to find out by looking at the power circuit board.

3. The logic control circuit board is the core of the inverter. It integrates large-scale integrated circuits such as CPU, MPU, RAM, EEPROM, etc., and has high reliability. All control terminals are closed at the same time, which will cause the inverter to fail in EEPROM. It only needs to reset the EEPROM.

4. The IPM circuit board includes drive and buffer circuits, as well as overvoltage and lack of protection circuits. The PWM signal from the logic control board enters the voltage driving signal into the IPM module through optical coupling. Therefore, while detecting the mode fast, the optical coupling on the IPM module should also be measured.

V. Inverter cooling system for packing equipment:

The cooling system mainly includes heat sinks and cooling fans. Among them, the life of the cooling fan is short. When the life of the cooling fan is approaching, the fan will vibrate, the noise will increase and finally stop, and the inverter will overheat and trip. The life of the cooling fan is limited by the bearing, which is about 10,000 ~ 35000h. When the inverter runs continuously, the fan or bearing needs to be replaced every 2 to 3 years. In order to extend the life of the fan, the fan of some products only runs when the inverter is running, not when the power is on.

Six, electromagnetic induction interference outside the inverter of packing belt equipment:

If there are interference sources around the inverter, they will invade the interior of the inverter through radiation or power lines, causing the control circuit to malfunction, causing abnormal work or shutdown, and even damage the inverter in severe cases. The specific methods to reduce noise interference are: all relays and contactor control coils around the inverter are equipped with absorption devices to prevent surge voltage, such as RC surge absorbers, and the wiring must not exceed 500px to minimize the wiring distance of the control circuit. It should be separated from the main circuit. The distance between the twisted joints of the control circuit wiring of the inverter should be more than 15mm, and the distance from the main circuit should be 250px or more. The cross-sectional area of the conductor ensures that the line voltage drop is within 2%. At the same time, an inverter output reactor should be installed to compensate the charging current of the distributed capacitance caused by the long-distance conductor. The grounding terminal of the inverter should be grounded according to the regulations. It must be reliably grounded at a dedicated ground point. It cannot be used with welding and power grounding to install a radio noise filter at the input end of the inverter to reduce the input harmonics. The noise impact of the equipment is also installed at the output of the inverter with a radio noise filter to reduce line noise at its output.

Seven, the impact of the installation environment of the inverter of packing equipment:

The inverter is an electronic device device, which has strict requirements on the installation environment, and has detailed requirements on the installation and use environment in its manual. In special cases, if these requirements cannot be met, corresponding suppression measures must be used as far as possible: vibration is the main cause of mechanical damage to electronic devices. For large vibration shocks, rubber and other vibration-proof measures should be used. Gases and dust will cause short circuit of rust, poor contact, and reduced insulation of electronic devices. As a precautionary measure, the control board should be treated with anti-corrosion and dust-proof, and the use of closed structure temperature is an important factor affecting the life and reliability of electronic devices. Especially for semiconductor devices, install air conditioners or avoid direct sunlight according to the environmental conditions required by the device. In addition to the above, it is also necessary to regularly check the air filter and cooling fan of the inverter. For special high and cold occasions, in order to prevent the microprocessor from working normally due to low temperature, it is necessary to take necessary measures such as installing an air heater.

8. The power supply of inverter of packing belt equipment is abnormal:

1. The power supply abnormality is roughly divided into the following three types: phase loss, low voltage, power failure, and sometimes their mixed forms. The main causes of these anomalies are mostly caused by wind, snow, and lightning strikes on power transmission lines, and sometimes because of short circuits to ground and interphase shorts in the same power supply system. Lightning strikes vary greatly by region and season. In addition to voltage fluctuations, some power grids or units that generate electricity by themselves also experience frequency fluctuations, and these phenomena sometimes recur in a short period of time. In order to ensure the normal operation of the equipment, corresponding requirements are also imposed on the power supply of the inverter.

2. If there are nearby devices such as electric motors and induction cookers, in order to prevent the voltage drop when these devices are put in, the power supply should be separated from the power supply of the inverter to reduce mutual influence.

3. For equipment that can continue to operate after instantaneous power failure, in addition to selecting a suitable price inverter, the speed reduction ratio of the motor load should also be considered in advance. When the inverter and the external control circuit both use the instantaneous power failure compensation method, after the voltage loss is restored, the speed measurement motor is used to prevent the overcurrent during acceleration.

4. For equipment that requires continuous operation, the inverter should be equipped with an uninterruptible power supply device that automatically switches. Like a frequency converter with a diode input and a single-phase control power supply, it can continue to work although it is in a phase loss state, but the current of individual devices in the rectifier is too large, and the pulse current of the capacitor is too large. The life and reliability of the device cause adverse effects, so it should be checked and dealt with as soon as possible.

Nine, lightning protection and induction lightning of inverter with packing equipment:

Lightning strikes or shock voltages induced by lightning strikes can sometimes cause damage to the drive. In addition, when there is a vacuum circuit breaker on the primary side of the power supply system, short-circuit opening and closing will generate a higher surge voltage. In order to prevent overvoltage damage due to surge voltage, it is usually necessary to pressurize the absorption device such as a thermistor at the input end of the inverter. Vacuum circuit breaker should be added with RC surge absorber. If there is a vacuum circuit breaker on the primary side of the transformer, in the control sequence, ensure that the inverter is disconnected before the vacuum circuit breaker operates.


Qingdao Mountain Plastic extruding Equipment Co., Ltd.

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Address:Nanguan Industrial Park, Jiaozhou, Qingdao, Shandong, China  TelePhone:  MobilePhone:+8613606307135