The maintenance of frequency converter often encounters the problem that the frequency cannot be raised
One frequency converter is in normal state, but it can not be adjusted to high-speed operation. After inspection, the frequency converter has no fault, the parameter setting is correct, the speed control input signal is normal, and the DC bus voltage of the frequency converter is only The normal value is about 450V, 580-600v, and the input side is tested again. One phase is missing. The fault is caused by the poor contact of one phase of an air switch on the input side. Why can the inverter still work in the low-frequency section without alarming? In fact, when the frequency converter is short of one phase input, it can work. The lower limit of bus voltage of most frequency converters is 400V, that is, when the DC bus voltage drops below 400V, the frequency converter will report the DC bus low voltage fault.
When two-phase input, DC bus voltage is 380 * 1.2 = 452v “400V. When the frequency converter is not running, the DC voltage can also reach the normal value due to the function of the flat wave capacitor. The new frequency converter adopts PWM control technology, and the work of voltage regulation and frequency modulation is completed in the inverter bridge, so the input phase loss can still work normally in the low frequency segment, but because the input voltage is low and the output voltage is low, the torque of the asynchronous motor is low, and the frequency cannot be removed.
In case of such fault display, first check whether the acceleration time parameter is too short, whether the torque lifting parameter is too large, and then check whether the load is too heavy. If there is no such phenomenon, the current transformer at the output side and the Hall current detection point at the DC side can be disconnected and operated after reset to see if there is over-current phenomenon. If so, it is likely that 1pm module has fault, because 1pm module contains over-voltage, under voltage, overload, overheating, phase loss, short circuit and other protection functions, and these fault signals are controlled by the module The output FN pin of the pin is transmitted to the microcontroller. After the microcontroller receives the fault information, on the one hand, the pulse output is blocked, on the other hand, the fault information is displayed on the panel, and the 1pm module is generally replaced.
Why can’t the frequency of frequency converter be adjusted up? How to solve it?
The frequency of the frequency converter can not jump up. First of all, let’s see the no-load situation, and do not connect the motor first.
1. For a frequency converter, there is a frequency range setting, such as the maximum output frequency of parameters and the upper limit of operation frequency. The maximum output frequency can be determined according to the structure of the frequency converter and can be queried according to the manual, such as 0 ~ 400.00hz. The upper limit of operation frequency is the upper limit of the output frequency of the frequency converter, less than or equal to the maximum output frequency. How to set the frequency limit of the frequency converter is too low You can’t even jump up.
2. Check whether the frequency regulation mode matches the frequency command according to the frequency setting mode. For example, the frequency converter sets communication frequency modulation, while the program writes analog quantity regulation. The frequency command generally includes local regulation (keyboard potentiometer analog quantity regulation), external analog quantity control (current or voltage mode), high-speed pulse setting, multi-stage speed setting, PID control and communication control After confirming the command, check whether the wiring mode is correct, such as positive and negative pole, com terminal, communication line AB, etc.
3. Check whether there is any error or correspondence between digital quantity and analog quantity output in the program, such as analog quantity control. Use a multimeter to measure whether the voltage or current output of Da module is the same as that calculated by us, and check whether Da module is damaged. If the communication indicator light in the communication control, such as reading and writing, is flashing or constantly on (according to the hardware), first ensure the normal communication, check whether the communication parameters, such as station number, verification, baud rate, are consistent with the settings of the upper computer, and whether the frequency converter can accurately receive the signal, etc.
4. Check whether the frequency converter is damaged, such as alarm or fault, and whether the terminal is damaged. After these are normal, the frequency can be adjusted and then connected to the motor. If the motor load is too large, the frequency may not be adjusted.
The reason and solution of frequency converter can‘t be adjusted
The frequency of the frequency converter cannot be adjusted. If there is no damage to the hardware, it is generally caused by the maximum torque output by the frequency converter is less than the load lifting torque. To be clear, the load capacity of the frequency converter is not good.
1. Acceleration time is too short
Theoretically, the longer the acceleration time is, the stronger the ability of lifting with load will be. The set acceleration time is too short. Some frequency converters will display overcurrent or overload overheat alarm, but some of them will not be displayed, just stuck in a certain frequency band.
2. V / F ratio is too large
Some frequency converters are also called torque raising. If this parameter is set too large, it will sometimes fail to start normally. If it is properly reduced, the problem will be solved
3. Vector control parameter mismatch
In the vector control mode, the internal resistance, inductance and other parameters of the motor need to be measured precisely, and the vector parameters of the frequency converter need to be well matched. After a period of operation, the motor parameters will overheat and cause deviation. At this time, the current will be too large to start the motor normally, and the frequency may also be stuck on a certain segment point. The problem can be solved by re optimizing the parameters.
4. Maximum frequency and maximum frequency set too low
Generally, these two parameters are set to the maximum value, but it can not be ruled out that some careless electricians have changed these two parameters, so it will also cause failure to raise the frequency.
5. Some special occasion parameters need to be matched
In some cases, the lowest frequency cannot be set too low. For example, in the constant pressure water supply system, after the lowest frequency is set to 0Hz, when the pressure of the water pump is low, the frequency converter starts to accelerate when it exceeds the starting frequency of the frequency converter, and the pressure cannot be increased all the time, and the frequency of the frequency converter can not be increased to 50Hz, only about 38hz. Repeatedly set and adjust PID, and the frequency cannot be increased all the time. Only when the lowest frequency of the frequency converter is set at about 15-20hz, the acceleration of the frequency converter can be met, and the pump can be kept at a constant pressure to a certain pressure position. Although the pressure meets the requirements of constant pressure, when water is not used, the frequency converter cannot stop completely, and the speed of the lowest frequency is always maintained.
This is because: in the constant pressure water supply system, the lowest frequency of the frequency converter cannot be set as 0Hz, generally at least around 20Hz, which is determined by the flow and head of the pump.
The solution is to set the dormancy frequency. When the frequency when the water pump does not use water (for example, 28hz) runs for several minutes, the water pump sleeps. When the pressure drops to 0.2-0.4mp lower than the set pressure, the water pump starts. Another method is to set up a timed water supply, which can be divided into several time periods. Generally, the constant pressure water supply controller has the functions mentioned above.
6. Hardware problems
After the transformer (Hall) of the frequency converter has problems, it is unable to measure the correct current normally, and similar situations may occur. In addition, when a measuring element on the main board is aged, this situation may also occur, which is often encountered during the maintenance of the frequency converter.