Why is the system pressure of variable frequency constant pressure water supply equipment unstable and prone to oscillation?
The system pressure is unstable, which may be caused by the following reasons:
1. The position of the pressure sensor to collect the system pressure is unreasonable. The pressure collection point is too close to the water outlet of the water pump, and the pipeline pressure is greatly affected by the flow rate of the water outlet. As a result, the pressure value fed back to the controller fluctuates, causing the system to oscillate.
2. If the system adopts the method of air pressure tank, and the pressure collection point is selected on the air pressure tank, it may also cause the system to oscillate. Air itself has a certain elasticity, and the solubility of gas in water changes with the change of pressure. There is a certain time difference between the feedback pressure of the water pump directly out of the water and the feedback pressure through the gas, which causes the system to oscillate.
3. The acceleration and deceleration time of the controller does not match the power of the water pump motor. Generally speaking, the greater the power, the longer the acceleration and deceleration time. For this parameter, users can select several data for debugging. For example, 15KW is generally between 10 and 20 seconds.
4. The acceleration and deceleration time of the controller and the inverter are inconsistent. The acceleration and deceleration time setting of the controller should be greater than or equal to the acceleration and deceleration time of the inverter.
Why does the small pump of the variable frequency constant pressure water supply equipment start and stop frequently?
This situation is for the small pump working at the industrial frequency. In the system, the 23rd and 24th parameters of the controller parameters "small pump pressure positive and negative errors" are set too small. After all the main pumps are turned off, when the actual pressure of the system is lower than the sum of the set pressure and the small pump pressure negative error, the small pump starts. As the system pressure rises, the actual pressure of the system is higher than the sum of the set pressure and the small pump pressure positive error, and the small pump is turned off by the system. Therefore, the solution to the problem is to increase this parameter by a certain value.
Why is the inverter output not zero when the water pump of the variable frequency constant pressure water supply equipment is switched?
The user should first make sure that all the control lines from the controller to the inverter are connected properly. If the inverter does not have a coasting stop input signal, the inverter must be set to a free coasting stop working mode. If the inverter has this signal input, make sure it is connected to the controller. Then, when the water pump switches, the controller will give the inverter a coasting stop signal, that is, an EMG signal. If the EMG signal line is not connected, it will directly cause the inverter to overload. Such phenomena must be absolutely prohibited, otherwise, it is easy to damage the inverter. If the EMG signal line is connected, please carefully check whether the line is connected firmly. After confirming that it is connected firmly and there is no line fault, use a multimeter to check whether the controller's EMG has output. If the EMG signal is not output when the controller is switching, it means that the controller is faulty. In addition, regardless of the type of inverter control method of the controller, the coasting stop mode is used when switching.
The analog output of the variable frequency constant pressure water supply equipment is abnormal, and the frequency converter operating frequency does not match the controller output.
First, determine what hardware is wrong. Put the controller into manual debugging state, and use a multimeter to measure the analog output value corresponding to the controller output of 0Hz and 50Hz. If the analog output value of the controller is greater than 30mV at 0Hz, or less than the voltage value of the controller's parameter calibration item 10 at 50Hz (please make sure the analog output gain is 100%), it means that there is a problem with the controller output. If the output remains unchanged as the frequency of the controller changes, it means that the analog output circuit of the controller is damaged; if the analog output value also changes, but cannot reach the maximum value, it can be solved by adjusting the analog output gain. Secondly, if the output value of the controller is normal, when the controller output reaches the voltage value of the parameter calibration item 10, the inverter cannot reach 50Hz, indicating that there is a problem with the setting value of the inverter, which can be solved by adjusting the frequency gain of the inverter.
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