1 Introduction
In order to save energy , reduce the cost, frequency conversion water supply usually adopts multi-pump parallel constant pressure variable water supply. This is because: â‘ a variable frequency pump and more than one frequency pump in parallel, can achieve constant pressure variable flow water supply, but requires variable frequency pump is one of the largest pump; â‘¡ inverter price and its power is proportional to multi-pump Parallel water supply reduces the power of each pump and correspondingly reduces the power of the inverter, which can reduce the cost. (3) The power supply of multiple pumps in parallel reduces the power of a single pump, which can significantly improve the energy saving effect when a pump is frequency-fed.
2. Frequency control water pump stop the best solution
From domestic and foreign literature and product samples, the best multi-pump constant pressure water pump to solve the control program is:
When the water flow is less than a pump rated flow, the same pump constant pressure water supply. Centrifugal pump theory, in similar conditions, the hydraulic power of the pump is proportional to the cubic speed. When the water flow is close to zero (but constant pressure), the pump speed is the lowest, and its power is also the smallest. For common centrifugal pumps, variable frequency constant pressure water supply at zero flow consumption of power is about the same size constant speed pump rated power of 1/4 or less (with the pump Q, H characteristics, constant pressure value, etc. ), But long-term inverter pump running at zero flow and consume energy in the end is a drawback, after all, when the pump power is larger, this shortcoming is more prominent.
In order to make the frequency conversion pump can stop the pump when there is no water, in order to save energy and reduce the pump wear, the foreign frequency converter (with multi-pump parallel constant pressure water supply control function) adopts such a control scheme that when the frequency conversion pump speed (frequency) When reduced to near zero flow threshold, the drive sends a command to stop the variable frequency pump pump. A small pressure tank is connected to the pipe network system. When the frequency conversion pump stops pumping, the pressure tank maintains the water supply. When the water supply pressure is reduced to a certain set value, the inverter accepts the pressure information to enable the variable frequency pump to start up and resume constant Pressure water supply. In the actual water supply, do not want to pump speed immediately reduced to zero flow threshold immediately stop the pump, but after a certain period of time, after the judge and confirmed no water before stopping the pump. To this end, you can set the computer control program to determine the program to achieve this goal. The specific method: When the inverter pump speed (frequency) reduced to zero flow threshold and continued for T time (T is the judgment time, can be set according to need) computer issued a command to stop variable frequency pump, the frequency conversion pump stop, this function is called Frequency pump automatic sleep function. During the stoppage of the pump, if someone uses water and causes the pipe network pressure to drop, when the pressure drops to the pump pressure (the pressure value can be set as required), the computer accepts the pressure information, and instructs the variable frequency pump to start automatically and resume constant pressure water supply , This function is called frequency pump automatic wake-up function.
It is understood that most of the domestic manufacturers of frequency conversion water supply equipment in order to make the frequency of water supply in the small flow of water can be better to save electricity and stop pumping without water in the water supply system set up a small pressure tank and a small working frequency Pump.
The author believes that the use of small work-frequency pump and small pressure tank there are more problems with the program, it is better to use automatic pump frequency sleep and wake-up program. The intelligent frequency conversion water supply equipment developed and manufactured by our company has successfully applied the automatic sleep and automatic wake-up scheme of the frequency conversion pump and proved to be very successful after being tested and delivered to users.
When the power of variable frequency constant pressure water supply pump is very large, for example, the power of one pump is 120kW, and the actual energy consumption of inverter pump is about 1/4 × 120 = 30kW when it is near zero flow. At this point, when a small flow of water, the pump frequency conversion will consume a considerable amount of electricity. From the energy considerations, the small flow of water should be supplied by a small pump. In order to save energy can use a variable frequency pump. The control system is designed like this:
(1) When using low flow rate, find the frequency when large pump is supplying water with constant pressure and small flow rate, and set as (Hz) Qmin.
(2) When a large pump supplies water at constant pressure and low flow rate, when Hz≤ (Hz) Qmin, an output relay (programmable) of the inverter works and sends a message to the dedicated PLC .
(3) PLC to accept the above information:
(a) Control the frequency converter to stop working;
(b) Switching the inverter on its output side after it stops: firstly , disengage the AC contactor of the variable frequency large pump and then connect the small pump of small power (eg 30kW);
(c) After switching on the output side of the inverter, restart the inverter to resume constant pressure variable water supply.
(4) Driven by the inverter, a small pump (eg 30kW) is used for low-pressure constant-pressure water supply. In this case, the small pump has the function of automatic sleep and automatic wake-up, and has the best energy-saving effect of small-volume water supply.
(5) When the water flow increases, the output frequency of the inverter rises. When Hz = (Hz) Qmin, a programmable output relay of the inverter is working. The work of the entire water supply system (2), (3) described, the water is still a small pump constant pressure water supply unchanged.
(6) When the water flow continues to increase, the inverter output frequency continues to rise, when Hz = (Hz) Qmin + ΔQ Another programmable output relay inverter work and send a message to the dedicated PLC.
(7) PLC to accept the above information
(a) Control the frequency converter to stop working;
(b) After stopping the inverter, perform the following switching operations on its output side: first, disengage the AC contactor of the small pump, and then connect the 120kW large pump to the inverter;
(c) After switching on the output side of the inverter, restart the inverter to resume constant pressure variable water supply.
(8) driven by the inverter 120kW pump for small flow constant pressure water supply, for example by 3 large pumps in parallel, the maximum water supply power of up to 120 × 3 = 360kW.
3.ABB intelligent frequency of water supply equipment applications
The inverter pump's automatic sleep and automatic wake-up control scheme has been applied to ABB drives with PFC macro (pump and fan control). In automatic sleep, the pump stops, does not consume electricity, with the best energy-saving effect. During the pump-off period, a small air pressure tank is provided in the system to maintain the water supply, and the small pressure tank maintains water supply during the automatic sleep of the pump. When the pressure tank pressure is reduced to a certain set value, the variable frequency pump automatically wakes up and resumes the constant pressure water supply.
The above functions of ABB inverter can be used to design the following series of intelligent frequency conversion water supply equipment:
(1) YLD-BP-S series of intelligent frequency of living water supply equipment.
When the water flow rate is less than the rated flow of a pump, variable frequency constant pressure variable pump B1 variable water supply; when the water flow is greater than a pump in the case of power frequency rated flow, frequency pump B21 automatic input and pump B1 in parallel Constant pressure variable water supply (When the variable pressure variable water supply, then each input frequency pump, the constant pressure value increased by a step ΔP, ΔP can be set on demand).
When the water flow to further reduce the frequency of the pump B1 automatically down to maintain constant pressure water supply. When the water flow is near zero, as determined by the debugger, the variable frequency pump operates at low speed near zero flow. When the low speed running T time (T value can be set, change), the frequency conversion pump stops (sleeps) automatically, the pressure tank maintains the water supply; when the pressure tank pressure drops to a certain set value, the frequency conversion pump starts automatically To maintain constant pressure water supply.
ABB drives with constant pressure (quasi-constant pressure) water supply control functions (ABB drives with PFC application macros) have the above control functions. A programmable output relay of this frequency converter drives a power frequency pump. When the number of frequency pump more than the number of programmable output relays, ND10 module can be used to expand.
(2) YLD-BP-X series of intelligent frequency power frequency fire water supply equipment .
B0 for the frequency conversion pump, controlled by a constant pressure water supply control inverter
B1, B2, B3 for the frequency fire pump , controlled by the PLC
Usually by the frequency conversion pump to the fire water pipe to make it in a state of fire preparedness. When the pipe network regulator to the set pressure, the regulator pump flow close to zero and maintain the time T (T can be set), the inverter pump automatically stop the pump (sleep) to rest, by the pressure tank to maintain regulation; when When the pressure of the fire pipe network drops to a certain set value, the inverter pump starts automatically and resumes the constant voltage regulator (auto wake-up). Frequency regulator is intermittent work, stop a long time, no need to set up a backup pump to reduce costs.
After receiving the fire signal, the main fire pump controlled by PLC (the first one) starts at the power frequency and put into fire protection. Fire stations and other fire pumps (including fire reserve pump) installed in the fire pipe network pressure gauge automatic control or automatic exit. Specific control methods are as follows: Under the condition that the main fire pump has been put into operation, if the pipeline pressure is insufficient (lower than the minimum fire pressure set by the electric contact pressure gauge), then the PLC will control the next fire pump (including spare pump ) Automatically put in to provide adequate firefighting flow.
Fire end, PLC can accept manual instructions, stop the fire (all fire pump stop pump).
3.ABB intelligent frequency of water supply equipment applications
The inverter pump's automatic sleep and automatic wake-up control scheme has been applied to ABB drives with PFC macro (pump and fan control). In automatic sleep, the pump stops, does not consume electricity, with the best energy-saving effect. During the pump-off period, a small pressure tank is provided in the system to maintain water supply, and the small pressure tank maintains water during the automatic sleep of the pump. When the pressure tank pressure is reduced to a certain set value, the variable frequency pump automatically wakes up and resumes the constant pressure water supply.
The above functions of ABB inverter can be used to design the following series of intelligent frequency conversion water supply equipment:
(1) YLD-BP-S series of intelligent frequency of living water supply equipment.
When the water flow rate is less than the rated flow of a pump, variable frequency constant pressure variable pump B1 variable water supply; when the water flow is greater than a pump in the case of power frequency rated flow, frequency pump B21 automatic input and pump B1 in parallel Constant pressure variable water supply (When the variable pressure variable water supply, then each input frequency pump, the constant pressure value increased by a step ΔP, ΔP can be set on demand).
When the water flow to further reduce the frequency of the pump B1 automatically down to maintain constant pressure water supply. When the water flow is near zero, as determined by the debugger, the variable frequency pump operates at low speed near zero flow. When the low speed running T time (T value can be set, change), the frequency conversion pump stops (sleeps) automatically, the pressure tank maintains the water supply; when the pressure tank pressure drops to a certain set value, the frequency conversion pump starts automatically To maintain constant pressure water supply.
ABB drives with constant pressure (quasi-constant pressure) water supply control functions (ABB drives with PFC application macros) have the above control functions. A programmable output relay of this frequency converter drives a power frequency pump. When the number of frequency pump more than the number of programmable output relays, ND10 module can be used to expand.
(2) YLD-BP-X series of intelligent frequency power frequency fire water supply equipment .
B0 for the frequency conversion pump, controlled by a constant pressure water supply control inverter
B1, B2, B3 for the frequency fire pump , controlled by the PLC
Usually by the frequency conversion pump to the fire water pipe to make it in a state of fire preparedness. When the pipe network regulator to the set pressure, the regulator pump flow close to zero and maintain the time T (T can be set), the inverter pump automatically stop the pump (sleep) to rest, by the pressure tank to maintain regulation; when When the pressure of the fire pipe network drops to a certain set value, the inverter pump starts automatically and resumes the constant voltage regulator (auto wake-up). Frequency regulator is intermittent work, stop a long time, no need to set up a backup pump to reduce costs.
After receiving the fire signal, the main fire pump controlled by PLC (the first one) starts at the power frequency and put into fire protection. Fire stations and other fire pumps (including fire reserve pump) installed in the fire pipe network pressure gauge automatic control or automatic exit. Specific control methods are as follows: Under the condition that the main fire pump has been put into operation, if the pipeline pressure is insufficient (lower than the minimum fire pressure set by the electric contact pressure gauge), then the PLC will control the next fire pump (including spare pump ) Automatically put in to provide adequate firefighting flow.
Fire end, PLC can accept manual instructions, stop the fire (all fire pump stop pump).
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