The author has been pursuing electrical engineering work since graduating from university. The types of inverters used and maintained in the workshop include Sanken, Fuji, CT, Siemens, and Danfoss. The power is from 0.75KW to 110KW; the control mode is switch and analog. From the normal use of the inverter and fault repair have some experience.
First, the correct use of the inverter should pay attention to 1, the ambient temperature has a great impact on the service life of the inverter. If the ambient temperature is 10°C per liter, the life of the inverter will be reduced by half. Therefore, the ambient temperature and the heat dissipation of the inverter must be solved.
2, the correct wiring and parameter settings. Before installing the inverter, you must familiarize yourself with its manual, master its usage, precautions, and wiring; after installation, set the parameters correctly according to the use.
3, pay attention to the relationship between speed and head. The choice of the motor and its best work section are more important issues. If the inverter runs below 5Hz for a long time, the motor heating becomes a prominent problem.
4, V / f control is a constant torque adjustment. The vector control increases the output torque of the motor in proportion to the square of the voltage, thereby improving the output torque of the motor at low speed.
5. If the system is operated by the power frequency/frequency conversion switching mode, the interlock between the power frequency output and the variable frequency output must be reliable. And stop the pump, power frequency / frequency conversion switch must stop the inverter, and then operate the contactor. Since the contact sticking and the extinguishment of the arc of the large-capacity contactor require a certain amount of time, the order and time of the above switching must be considered comprehensively.
6, the external control signal failure problem. There are generally several situations: Incorrect signal mode, incorrect terminal wiring, incorrect parameter settings, or external signal itself.
7. The difference between over-current trip and overload trip. Overcurrent is mainly used to protect the inverter, while overload is mainly used to protect the motor. Because the capacity of the inverter sometimes needs to increase one or two gears compared to the capacity of the motor. In this case, the inverter will not necessarily over-current when the motor is overloaded. Overload protection is performed by the internal electronic thermal protection function of the inverter. When presetting electronic thermal protection, the percentage of the ratio of “current draw ratioâ€, that is, the rated current of the motor and the rated current of the inverter should be accurately preset.
8, interference problems.
(1) Good grounding. The ground wire of a strong electric control system such as a motor must be reliably grounded through the busbar. The control system is preferably grounded independently and has a ground resistance of less than 1Ω. The sensor, I/O interface shields are connected to the control system's control ground.
(2) Install EMI filters, common-mode inductors, and high-frequency magnetic rings on input power supplies such as meters.
(3) Adding EMI filter to the input of the inverter can effectively suppress the conduction interference of the inverter to the power grid. Adding input AC and DC reactors can increase the power factor, reduce harmonic pollution, and have a good comprehensive effect. When the distance between some motors and the inverter exceeds 100m, an AC output reactor must be added on the inverter side to solve the problem of external radiation interference caused by the reduction of leakage current protection due to the distribution parameters of the output conductors to ground.
Second, the use of frequency converter in the failure and processing 1, frequency inverter can not reach the normal frequency (40HZ). A SAMCO-i inverter, through an external terminal analog control, a frequency can only reach 20HZ, in turn check the parameters, the highest frequency and the upper frequency are 50HZ, visible parameters no problem, immediately change the panel to a given frequency, The maximum frequency can be run to 50HZ. From this point of view, the problem lies in the analog input circuit or the original device of the inverter itself. Check the thermal resistance with a multimeter. The linearity is very good. There is no problem. After turning on the inverter, it is found that a chip capacitor is damaged and the inverter is replaced. Back to normal.
2. Frequent inverter over-current alarm.
(1) Incorrect parameter settings. If the inverter acceleration time is set too short, the output frequency of the inverter will change far more than the frequency of the motor. When the inverter starts, it will trip due to overcurrent. Adjusting the acceleration time according to different load conditions can eliminate this fault.
(2) A short circuit occurs in the output load. If a Fujitsu inverter trips, the cable head of the contactor at the output side is rusted and loosened, and an arc occurs at the time of starting, resulting in a protective action.
(3) Damage to the detection circuit will also show a transitional alarm. The Hall sensor is affected by environmental factors such as temperature and humidity, and the working point drifts.
(4) Excessive load may also be caused. Such as a Siemens M420 inverter, due to mechanical stuck.
3. A Siemens 6SE7036 inverter trips after a certain period of time. "F023" (inverter exceeds the limit temperature) is displayed. Check is because the fan has been damaged due to an overheated fan and the fuse is replaced. Replace the fuse.
4, a Siemens 6SE7036 inverter PMU panel LCD display letter "E", the inverter can not work, according to the P keyboard and re-stop power are invalid, check the operating manual is also not related instructions, check the external 24VDC power supply At that time, it was found that the voltage was low. After changing one power supply, the inverter returned to normal.
5, inverter undervoltage, overvoltage alarm, which is caused by the main power; also caused by damage to the machine detection circuit.
(1) Faults such as 6SE7036 inverter F008 (Ud(2) Overvoltage tripping when a SAMCO-I inverter is stopped. The inverter has many setting parameters. If the individual parameters are not set properly, the inverter will not work properly. Overvoltage occurs when the inverter stops. The main reason is that the deceleration time is too short (if there is no braking resistor and brake unit) the motor speed is greater than the synchronous speed, the rotor electromotive force and current increase, the motor is in the power generation state, and the energy returned is connected in parallel with the high-power switch tube. The diode flows back to the DC link, causing the DC bus voltage to rise. After adjusting the time parameters, the fault is eliminated.
6, a Siemens MM3 inverter, often "no reason" shutdown. It may be normal to turn on the power again. After comparing and observing, it is found that the main contactor does not pull normally after power on, and sometimes it will lose power and jump. As a result, it was found that a filter capacitor from the switching power supply to the contactor leaked, resulting in a low voltage. If the power supply voltage is too high, then the problem is not significant. If the supply voltage is too low, the contactor will not be properly picked up and cause an untimely shutdown. .
7. A nuclear company uses the Siemens M420 inverter. During the operation, it often stops suddenly, restarts, and can run. Check the inverter's parameter settings are correct. Suspected PROFIBUS-DP line problem, put a PROFIBUS-DP line again, the failure still exists. Connect the programmer to check the start condition of the inverter. All start points cannot be broken. Only the point at which the nuclear authority calls the communication between the PLC and the master PLC may break. After a few days of observation, this point is broken in a short time. It returned to normal again, so I used a power-off delay timer to handle this failure.
8, four 22KW motors originally used Y-start, instead of using Fuji inverter. The "U002" overvoltage alarm often appears. Check the line voltage, are within 380 ± 10%, the parameters are also normal, normal after reset, but it will not take long for this same fault, and finally consult the inverter instruction manual, Fujitsu inverter voltage is not set in the parameter settings, and It is set by a jumper. After the jumper is reconnected, the fault is resolved.
9. The inverter cannot be on the PROFIBUS-DP network. The red light on the inverter is always on. Check several parameters P0700, P0719, P0918, and P1000 of the PROFIBUS-DP on the inverter. It can only be the problem of network cable or network card. For a network card, the problem is solved.
In short, in the common faults of inverters, there are not many problems with large components such as IGBT power modules, and the percentage of faults caused by their peripheral circuits is large. During routine maintenance, check the grid voltage and improve the surrounding environment of the inverter, motor, and wiring. Periodically remove dust from the inverter and check that the terminals are tight. Minimize the fault rate of the inverter by enhancing device management. At the same time do a good job of recording faults, and it is very important to pay attention to analyzing the load status, operation process, and failure phenomena of the faults, which is conducive to the future work.
First, the correct use of the inverter should pay attention to 1, the ambient temperature has a great impact on the service life of the inverter. If the ambient temperature is 10°C per liter, the life of the inverter will be reduced by half. Therefore, the ambient temperature and the heat dissipation of the inverter must be solved.
2, the correct wiring and parameter settings. Before installing the inverter, you must familiarize yourself with its manual, master its usage, precautions, and wiring; after installation, set the parameters correctly according to the use.
3, pay attention to the relationship between speed and head. The choice of the motor and its best work section are more important issues. If the inverter runs below 5Hz for a long time, the motor heating becomes a prominent problem.
4, V / f control is a constant torque adjustment. The vector control increases the output torque of the motor in proportion to the square of the voltage, thereby improving the output torque of the motor at low speed.
5. If the system is operated by the power frequency/frequency conversion switching mode, the interlock between the power frequency output and the variable frequency output must be reliable. And stop the pump, power frequency / frequency conversion switch must stop the inverter, and then operate the contactor. Since the contact sticking and the extinguishment of the arc of the large-capacity contactor require a certain amount of time, the order and time of the above switching must be considered comprehensively.
6, the external control signal failure problem. There are generally several situations: Incorrect signal mode, incorrect terminal wiring, incorrect parameter settings, or external signal itself.
7. The difference between over-current trip and overload trip. Overcurrent is mainly used to protect the inverter, while overload is mainly used to protect the motor. Because the capacity of the inverter sometimes needs to increase one or two gears compared to the capacity of the motor. In this case, the inverter will not necessarily over-current when the motor is overloaded. Overload protection is performed by the internal electronic thermal protection function of the inverter. When presetting electronic thermal protection, the percentage of the ratio of “current draw ratioâ€, that is, the rated current of the motor and the rated current of the inverter should be accurately preset.
8, interference problems.
(1) Good grounding. The ground wire of a strong electric control system such as a motor must be reliably grounded through the busbar. The control system is preferably grounded independently and has a ground resistance of less than 1Ω. The sensor, I/O interface shields are connected to the control system's control ground.
(2) Install EMI filters, common-mode inductors, and high-frequency magnetic rings on input power supplies such as meters.
(3) Adding EMI filter to the input of the inverter can effectively suppress the conduction interference of the inverter to the power grid. Adding input AC and DC reactors can increase the power factor, reduce harmonic pollution, and have a good comprehensive effect. When the distance between some motors and the inverter exceeds 100m, an AC output reactor must be added on the inverter side to solve the problem of external radiation interference caused by the reduction of leakage current protection due to the distribution parameters of the output conductors to ground.
Second, the use of frequency converter in the failure and processing 1, frequency inverter can not reach the normal frequency (40HZ). A SAMCO-i inverter, through an external terminal analog control, a frequency can only reach 20HZ, in turn check the parameters, the highest frequency and the upper frequency are 50HZ, visible parameters no problem, immediately change the panel to a given frequency, The maximum frequency can be run to 50HZ. From this point of view, the problem lies in the analog input circuit or the original device of the inverter itself. Check the thermal resistance with a multimeter. The linearity is very good. There is no problem. After turning on the inverter, it is found that a chip capacitor is damaged and the inverter is replaced. Back to normal.
2. Frequent inverter over-current alarm.
(1) Incorrect parameter settings. If the inverter acceleration time is set too short, the output frequency of the inverter will change far more than the frequency of the motor. When the inverter starts, it will trip due to overcurrent. Adjusting the acceleration time according to different load conditions can eliminate this fault.
(2) A short circuit occurs in the output load. If a Fujitsu inverter trips, the cable head of the contactor at the output side is rusted and loosened, and an arc occurs at the time of starting, resulting in a protective action.
(3) Damage to the detection circuit will also show a transitional alarm. The Hall sensor is affected by environmental factors such as temperature and humidity, and the working point drifts.
(4) Excessive load may also be caused. Such as a Siemens M420 inverter, due to mechanical stuck.
3. A Siemens 6SE7036 inverter trips after a certain period of time. "F023" (inverter exceeds the limit temperature) is displayed. Check is because the fan has been damaged due to an overheated fan and the fuse is replaced. Replace the fuse.
4, a Siemens 6SE7036 inverter PMU panel LCD display letter "E", the inverter can not work, according to the P keyboard and re-stop power are invalid, check the operating manual is also not related instructions, check the external 24VDC power supply At that time, it was found that the voltage was low. After changing one power supply, the inverter returned to normal.
5, inverter undervoltage, overvoltage alarm, which is caused by the main power; also caused by damage to the machine detection circuit.
(1) Faults such as 6SE7036 inverter F008 (Ud(2) Overvoltage tripping when a SAMCO-I inverter is stopped. The inverter has many setting parameters. If the individual parameters are not set properly, the inverter will not work properly. Overvoltage occurs when the inverter stops. The main reason is that the deceleration time is too short (if there is no braking resistor and brake unit) the motor speed is greater than the synchronous speed, the rotor electromotive force and current increase, the motor is in the power generation state, and the energy returned is connected in parallel with the high-power switch tube. The diode flows back to the DC link, causing the DC bus voltage to rise. After adjusting the time parameters, the fault is eliminated.
6, a Siemens MM3 inverter, often "no reason" shutdown. It may be normal to turn on the power again. After comparing and observing, it is found that the main contactor does not pull normally after power on, and sometimes it will lose power and jump. As a result, it was found that a filter capacitor from the switching power supply to the contactor leaked, resulting in a low voltage. If the power supply voltage is too high, then the problem is not significant. If the supply voltage is too low, the contactor will not be properly picked up and cause an untimely shutdown. .
7. A nuclear company uses the Siemens M420 inverter. During the operation, it often stops suddenly, restarts, and can run. Check the inverter's parameter settings are correct. Suspected PROFIBUS-DP line problem, put a PROFIBUS-DP line again, the failure still exists. Connect the programmer to check the start condition of the inverter. All start points cannot be broken. Only the point at which the nuclear authority calls the communication between the PLC and the master PLC may break. After a few days of observation, this point is broken in a short time. It returned to normal again, so I used a power-off delay timer to handle this failure.
8, four 22KW motors originally used Y-start, instead of using Fuji inverter. The "U002" overvoltage alarm often appears. Check the line voltage, are within 380 ± 10%, the parameters are also normal, normal after reset, but it will not take long for this same fault, and finally consult the inverter instruction manual, Fujitsu inverter voltage is not set in the parameter settings, and It is set by a jumper. After the jumper is reconnected, the fault is resolved.
9. The inverter cannot be on the PROFIBUS-DP network. The red light on the inverter is always on. Check several parameters P0700, P0719, P0918, and P1000 of the PROFIBUS-DP on the inverter. It can only be the problem of network cable or network card. For a network card, the problem is solved.
In short, in the common faults of inverters, there are not many problems with large components such as IGBT power modules, and the percentage of faults caused by their peripheral circuits is large. During routine maintenance, check the grid voltage and improve the surrounding environment of the inverter, motor, and wiring. Periodically remove dust from the inverter and check that the terminals are tight. Minimize the fault rate of the inverter by enhancing device management. At the same time do a good job of recording faults, and it is very important to pay attention to analyzing the load status, operation process, and failure phenomena of the faults, which is conducive to the future work.
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