Now water is generally used constant pressure water supply method: by a number of pumps in parallel with constant pressure water supply, common frequency conversion constant pressure water supply technical transformation program common are the following two.
According to the experience of use, scheme (1) saves initial investment but has poor energy saving effect. When the inverter is started to 50 Hz at the start, the power frequency is started, and then it is transferred to the energy-saving control. In the water supply system, only the water pump driven by the frequency converter is used, the pressure is slightly smaller, and the system has turbulent flow phenomena and losses.
Option (2) has a large investment, but it is 20% more energy-efficient than Option (1). The pump pressure of the pump is consistent and there is no turbulent flow loss. The effect is better.
When multiple pumps are connected in parallel to a constant pressure water supply, only one sensor is used in the signal series method. The advantages are as follows.
(1) Save costs. As long as a set of sensors and PID,
(2) Because there is only one control signal, the output frequency is the same, that is, the same frequency, so that the pressure is consistent, there is no turbulent loss.
(3) When the constant pressure water supply is used, when the flow rate changes, the number of pumps that are turned on will change according to PLC control. At least one station, two medium units, and three large units. When the inverter does not work, the circuit (current) signal is the path (with signal inflow, no output voltage, frequency).
(4) More beneficially, because the system has only one control signal, even if the three pumps have different inputs, the operating frequency is the same (that is, synchronous), and the pressure is also the same, so the turbulence loss is zero, that is, the loss is the minimum, so the energy saving The best results.
four. Some analysis of frequency converter for non-constant power type load:
(1) Due to the large starting torque of certain load characteristics, equipment that is difficult to start, such as extruders, washers, dryers, mixers, coating machines, mixers, large fans, pumps, Roots blowers, etc. It started smoothly. This is obviously more effective than the usual increase in starting frequency. Use this method in combination with the heavy load to change the light load measures, increase the current protection to the maximum, almost all equipment can start. Therefore, it is the most effective method to increase the starting torque by reducing the base frequency, which is also the most convenient method.
(2) The reduction of the substrate frequency when this condition is applied does not necessarily have to be reduced to 30 Hz. You can use a gradual decrease every 5 Hz, and the frequency of the drop arrives as long as you can start the system.
(3) The lower limit of the base frequency should not be lower than 30 Hz. From the perspective of torque, the lower the lower limit the greater the torque. However, it is also necessary to consider that the voltage rises too fast and the IGBT is damaged when the dynamic du/dt is too large. As a result of practical use, this torque-raising measure can be used safely and safely in the range of 50 Hz down to 30 Hz.
(4) Some people worry that, for example, the voltage has reached 380 V when the base frequency is lowered by 30 Hz. So when the normal work may need to reach 50 Hz, whether the output voltage jumps 380 V, so the motor can not stand, and the answer is that this phenomenon will not happen.
(5) Some people worry that if the base is lowered to 30 Hz, the voltage has reached 380 V. In normal operation, it may be necessary to reach a nominal frequency of 50 Hz when the output frequency reaches 50 Hz. The answer is that the output frequency can certainly reach 50 Hz.