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Constant pressure water supply engineering

Constant pressure water supply refers to the client at any time, regardless of the size of water pipe network pressure, always remains substantially constant. In the constant pressure water supply system, in order to maintain substantially constant pressure of the pipe network, need transducer according to the given pressure signal and the pressure of the pipe network compares the feedback signal to adjust the pump speed, to control the network pressure purpose.

1Hardware structure:

The system uses a frequency converter and a pressure sensor is used as the central control unit, to achieve a desired function. Pressure sensor for CYG200 series pressure sensor. Pressure using a liquid crystal digital meter display, range from 0 to0.5Mpa, corresponding to the feedback current4 ~ 20Ma,24VDC0.25%FS power supply type, level, pressure sensor feedback current I ( mA ) and the pressure of the pipe network H ( Mpa ) and the relationship between them is: I =32H+4, I - feedback current, mA; H - pipe network pressure, Mpa; for example: when H = 0.35, I feedback current = 32 * 0.35+4= 15.2( mA ), as the motor power is 45KW, the rated current for the 98A, can choose to ShiJia A500 series inverter.

2system principle:

First need to set the PI function effectively, and then determine the PI controller signal type as the feedback signal to the input, the set value given by the panel. Constant pressure water supply system as shown in figure:

For given parameters of frequency speed actual pressure

When the actual pressure feedback network by the given pressure were compared, when the pressure of a pipe network is low, increasing the output frequency, pump speed faster, so that the pipe network pressure rise. Conversely, pump speed slow down, make the pipeline pressure drop, in order to maintain the stable water supply pressure.

The 3system is introduced

In order to ensure the reliability of the system, must provide the power / frequency of two kinds of mode of operation, to reduce the frequency converter fault or an equipment maintenance and other reasons caused by the inability to supply the phenomenon, demand control system must be set up manually power mode of operation, the system uses the switch to achieve power / frequency conversion between, in variable frequency operation mode, AC contactor is used between the interlocking control mode, empathy, the power mode of operation, the AC contactor is adopted among the interlock control mode.

(1) the system of main circuit

Inverter constant pressure water supply system water pump adopts a preparation with a way that require a water pump, a stand, when using the pump failure or maintenance, another immediately put into operation, the interruption of water supply. And two pumps are required and in frequency converter drive, inverter fault, can automatically realize the power / frequency switching.

(2) the control system structure

A. The system for preparing a power / frequency conversion, automatic constant pressure water supply system;

B. This system pressure through the panel set, according to the characteristics of the water pump0 ~50HZ corresponding0.5Mpa, for example: if the set pressure of the pipe network to the 0.4Mpa, pressure set value at its rated value80%;

C. This system has the motor over voltage, under voltage, over current, converter overheating protection function;

The D. In order to ensure the system safety, in addition to set frequency converter in electronic thermal protection function, but also the thermal relay for motor thermal protection.

4characteristics of the system

(1) Mitsubishi inverter control way has the advantages of low current ripple, low torque ripple, low motor temperature rise, and improve the power factor, according to the actual operation of the system, the power factor of long-term to maintain in 0.95 above.

(2) as a " one to two" control, the hardware investment cost less, have a higher price competitive advantage.

(3) the system without the user places and application environment, has strong versatility and flexibility. Based on the field observation, the steady state network pressure to a set value + 2%.

SHiJia Inverter in constant pressure water supply system application has been successful, the test data display system control and good quality, fast response speed. Realization of the design function, ensure the system stability and security. In the long run to achieve a good effect of energy saving, energy saving of 20% to 30%.

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