3. functions introductions
This kind of frequency conversion cabinet is one kind of low cost as soon as tows three control modes, its process is 1 pumps the velocity modulation movement to the full load when still reaches in arrives the hypothesis pressure, PLC pumps the current movement transforms into the labor frequency, again softly starts 2 to pump, starts to modulate velocity the direct link hypothesis pressure value, like still could not answer the purpose then pumped 2 also transfers the labor frequency movement, after 3 pumped the soft start to put the velocity modulation operation, achieved the hypothesis pressure value, reduced pumped when according to 3, 2, 1 pumps the smooth execution. So circulates the reciprocation, the realization closed loop regulating control constant pressure water supply. Then saves the energy, also may achieve the economy durably, may realize the not interrupted water supply or automatic fixed time supplies water, equipment movement reasonable, reliability high, disposition nimble, the operation maintenance is simple.
4. systems principle of work
This system work flow is: Will transport passes on the pressure gauge to supply water in the pipe network dynamic pressure signal direct input to the frequency changer simulation quantity input 端子, took the frequency conversion closed loop PID control the feedback quantity, the frequency conversion velometer demand signal will assign by control 端子 X1-X4, because the frequency conversion water supply will not be high to the frequency precision request, 4 端子 might compose 16 levels of frequencies to assign the change. X1 - X4 controls the combination by PLC four outputs, simultaneously the PLC output spot may control the labor frequency/frequency conversion the cut. Its most important is uses the frequency changer FMP 端子, the output and the frequency become the proportion the pulse string, again inputs to SPB-PLC high-speed counting 端子, calculates the frequency changer the actual output frequency, compares after the PLC operation, realizes the nature cut which each pumps, truly achieves the constant pressure water supply the goal. When fire movement, presses down the fire prevention 按纽, the execution corresponding PLC procedure, all water pumps cut into the labor frequency movement by, guarantees the fire water used pressure.
5. equipment shapings
1. frequency changers: Selects the Japanese original installation Fuji electrical machinery FVR2.2E11S-4JE frequency changer. This model low noise, the torque big, the volume small, the function is strong, brings the PID function, may in each kind of situation use, be the low power high performance frequency changer first choice.
2. programmable forewords controllers: Selects the Fuji electrical machinery most newly to promote SPB series small PLC: NWOP30R-31 (16 enters /14), this machine characteristic as follows:
1. volumes exquisite, the function formidable, the processing speed quick, the variety is complete (20, 30, 40, 60 main engines, 16, 32 expansions);
2. direct belts expand, do not need to meet the power source in addition, most greatly may reach 124;
3. has from lifts the bolt 端子, the wiring is convenient, does not fall the bolt;
4. has outside each kind to meet the unit, like the simulation quantity (4 enters, 2, 3 enter /1), RS-232C, RS-485 communication unit, AS-I main line unit;
5. high-speeds counting may reach 100KHZ
6. software functions formidable:
(1) has each kind of 32 operational command;
(2) 40, 60 belts internal clock;
(3) has the floating point calculation function, and corresponding trigonometrical function operation function;
(4) has pulse control function and so on the PWM;
(5) has the multistage pitch to retain one's hold the function;
(6) has the matrix, PID, function and so on digital switch read-in;

3. low pressure electric appliances:
(1) air switch: Fuji electrical machinery EA33B/15A.
(2) contact device: Fuji electrical machinery SC-E03 nominal current 12A.
Thermal relay: The Fuji electrical machinery TK-E02/9-13A belt breaks protects.
6. concluding remark
This frequency conversion constant pressure water supply control cabinet may widely apply to the city and countryside each kind of type running water water supply system, high-rise construction water supply, domestic water and fire water supply industrial production operating mode closed loop water used constant pressure control.