Several questions about constant pressure water su

Several questions about constant pressure water supply control of frequency converter

Abstract: common problems and answers of constant pressure water supply control of frequency converter

key words: constant pressure water supply control of frequency converter Untitled Document 1. Is the system pressure unstable and easy to oscillate

answer: the system pressure is unstable, which may be caused by the following reasons:

a, there is a problem with the position of the pressure sensor collecting system pressure, the selection of the pressure collecting point is too close to the water outlet of the pump, and the pipeline pressure is too affected by the water outlet speed. Thus, the pressure value fed back to the controller fluctuates, causing system oscillation

b. In addition, if the system adopts the mode of air pressure tank, and the pressure collection point is selected on the air pressure tank, it may also cause system oscillation. Because the air itself has certain flexibility, and the solubility of the gas in the water changes with the pressure, there is a certain time difference between the water pump outlet and the pressure transmitted through the gas, resulting in system oscillation

c, the acceleration and deceleration time of controller and frequency converter is inconsistent with the power of water pump motor. Generally, the greater the power, the longer the acceleration and deceleration time. This parameter allows users to select several more data for the test. For example, 15kw is generally between 10 and 20 seconds

2. Small pump starts and stops too frequently

answer: in the system, the 11th parameter in the parameters of the controller, that is, the stop pressure error of the small pump, is too small. After all the main pumps are shut down, when the actual pressure of the system is lower than the set pressure, the small pump will start. With the rise of system pressure, the actual pressure of the system is higher than the sum of the set pressure and the stop pressure error of the small pump, and the small pump is shut down by the system. Therefore, the solution to the problem is to increase this parameter by a certain value

3. The analog output is abnormal, and the operating frequency of the frequency converter is inconsistent with the output of the controller

answer: first of all, we should determine what the price of hard high configuration will be higher than that of low configuration. There is a problem. Put the controller into manual debugging state, and use a multimeter to measure the corresponding analog output values when the controller outputs 0Hz and 50Hz respectively. If the analog output value of the controller is greater than 30mV at 0Hz or less than the voltage value of the 5th parameter of the controller, which is similar to that of glass, it indicates that there is a problem with the output of the controller. There are several situations:

a. if the output remains unchanged with the frequency of the controller, it indicates that the analog output circuit of the controller is damaged

b. if the analog output value also changes, but cannot reach the maximum value, it can be solved by adjusting the VR3 potentiometer in the small window of the controller

secondly, if the output value of the controller is normal, when the controller output reaches the maximum value, the frequency converter cannot reach 50Hz, which indicates that there is a problem with the set value of the frequency converter, and the frequency gain of the frequency converter can be adjusted to solve it

4. When the water pump is switched, the output of the frequency converter is not zero. Why

answer: the user should make sure that all the control lines from the controller to the frequency converter are connected. When the water pump is switched, the controller will give the frequency converter a sliding stop signal, that is, EMG signal. Some users' EMG signal line is not connected, which directly leads to the above situation. This kind of phenomenon should be absolutely prohibited, otherwise, it is easy to damage the frequency converter. If there is an EMG signal line, please carefully check whether the wiring is solid. After confirming that the connection is solid and there is no line fault, use a multimeter to check whether the EMG of the controller has output. If the EMG signal is not output when the controller is switched, it indicates that it is the problem of the controller

5. How to connect the anti-interference wiring between the controller and the frequency converter

answer: in order to prevent the control signal lines of the controller and frequency converter from being interfered by the space electromagnetic field, shield wires can be connected to the outer layer of these control signal lines to improve the anti-interference ability of the system. Such wiring must be noted that only one point can be selected for the grounding point of the shield. Whether it is on the controller side or on the inverter side. In this way, the anti-interference ability of the system can be improved. If the shield wire is grounded at both ends, the potential difference will be generated on the shield wire, which will not improve the anti-interference ability of the system, but increase the external interference to the dry pulley of the controller and the electromechanical drive connection

6. How to solve the problem that the data of the controller flies or is occasionally incorrect

answer: this situation is caused by serious interference to the controller. Often, the working environment of the controller is relatively poor, and the interference signals come from many aspects. After modifying the state or parameters of the controller, the user must turn the black keyboard lock switch in the small window of the controller to the lock position. In this way, it not only prevents others from unconsciously modifying parameters, but also ensures that the system data will not run away. If the data is abnormal occasionally, the controller can automatically run without stopping, and the system stability pressure does not change. At this time, the controller can automatically read back the original data. If the controller can no longer work normally, the user can disconnect the power supply of the controller and restart it later, and the system will return to normal operation. If the user forgets to lock the keyboard lock switch and the setting data is rewritten, the user needs to reset the system parameters. After setting, pay attention to locking the switch

7. The contactor controlling the motor does not act, and the motor does not start

answer: first, check the output state of the controller reflected by the controller panel, which can be compared with the setting and operation indication state of the seven pumps on the panel described in the controller manual. If the indication state of the pump on the panel corresponding to the motor without action has output, the user will first check whether the external contactor wiring and the relay logic of the contactor are correct. If there is no problem, use a multimeter to measure the output of the corresponding relay of the controller. If the relay does not output a closed switch signal, it indicates that there is a problem with the relay output of the controller. If the corresponding pump indicated on the panel also has no output indication, please check the parameter setting of the controller and check whether the corresponding pump is set to the on state

8. The pressure sensor shows the pressure change, but the panel shows the pressure unchanged

answer: first, check whether the wiring of pressure sensor and controller is loose or has poor contact. If the above phenomenon does not exist, use a multimeter to measure the voltage value of the analog input port of the controller. First measure the voltage between SV terminal and GND terminal. If it is 5V, it indicates that the power supply providing the analog input port is normal, and then proceed to the next step. A 10k ohm sliding resistance can be connected to the three terminals of the input port of the controller, and the moving terminal is connected to P1, and then the voltage of P1 terminal and GND terminal of the controller can be measured