Boiler blast, induced draft and frequency conversion of water pump

Boiler blast, induced draft and frequency conversion of water pumps adopt Delta F-series inverters to control boiler blast and induced wind and constant pressure water supply

Row.
Control objects: Blast motor for blower and induction wind motor, constant pressure water supply motor, etc.

Equipment parameters: motor parameters of the customer site: blower motor power: 55KW wind turbine power 18.5KW

Constant pressure water pump 22KW

Control objective: to reform and form a good combustion conditions, improve the boiler combustion efficiency, reduce energy consumption and reduce

Sewage.

Frequency conversion control system design work principle:

This system can realize open/closed loop operation:
First, the control function

1. Wind control:
Through the control box panel Induced wind start Turn on the operation of the induced draft fan. The induced wind stops. Close the operation of the induced draft fan. After the induced draft fan starts running, it can have ¡. ¡ Wind speed ¡ Multi-segment selection switch to change the operating speed of the induced draft fan, the speed range can be adjusted between 10c/o-100c/o, divided into ten speeds in this interval, each stage speed has 10c/o upward increment, both as 10c/o, 20 c/o,¡ ¡ 90c/o, 100c/o, in
When 100c/o selects the gear, it is equivalent to the running speed under the power frequency state; at the same time, there is an ammeter to display the current of the current draught fan in time.
Operational control is shown in Figure 1 below:
2. Blower control:
Through the control box panel Blasting start ¡ Turn on the operation of the induced draft fan. The blast stopped. Close the operation of the induced draft fan. After the induced draft fan starts running, it can have ¡. ¡ Blast rate ¡ Multi-segment selection switch to change the operating speed of the induced draft fan, the speed range can be adjusted between 10c/o-100c/o, divided into ten speeds in this interval, each stage speed has 10c/o upward increment, both as 10c/o, 20 c/o,¡ ¡ 90c/o, 100c/o, in
When 100c/o selects the gear, it is equivalent to the running speed under the power frequency state; at the same time, there is an ammeter to display the current of the current draught fan in time.
Operational control is shown in Figure 1 below:
3. Water pump control:
Through the control box panel Pump start Turn on the operation of the induced draft fan. The pump stops ¡ Close the operation of the induced draft fan. After the induced draft fan starts running, it can have ¡. ¡ Pump speed Multi-segment selection switch to change the operating speed of the induced draft fan, the speed range can be adjusted between 10c/o-100c/o, divided into ten speeds in this interval, each stage speed has 10c/o upward increment, both as 10c/o, 20 c/o,¡ ¡ 90c/o, 100c/o, in
When 100c/o selects the gear, it is equivalent to the running speed under the power frequency state; at the same time, there is an ammeter to display the current of the current draught fan in time.
Induced wind control blower control pump control Current display row Start control row Stop the control row Rate selection Rank two, the main chain of the system:
1. Blower operating conditions: The blower is allowed to start running only when the induced draft fan is put into operation.
2. Frequency and industrial frequency chain. Frequency conversion operation with the original old frequency operation, chain control system.
3. When the frequency conversion system fails during operation, an alarm signal is issued to remind the on-duty personnel to deal with it in due course.
Third, the system composition:
1, boiler frequency conversion control configuration and system configuration: GGD control cabinet body 1000¡ 300 One Programmable Logic Controller (PLC) 1 Delta frequency converter 3 sets of induced frequency conversion power VFD185F43A
Blower frequency conversion power VFD550F43A
Pump frequency conversion power VFD220F43A
Main Circuit Breaker Set Indicator Light/Transfer Switch/Button AC Voltmeter, AC Ammeter, Transformer Control Power Supply Filter Schematic:
Frequency conversion control cabinet technical parameters and performance characteristics:
1. The main technical parameters:
(1) Main loop power supply: Three-phase five-wire system. 380V+10%.
(2) Control circuit voltage: 380V
(3) Negative pressure adjustment range: To ensure that a full combustion system is established.
(4) Steam pressure adjustment range: It depends on actual production requirements.
2. System performance characteristics:
(1) Operation mode selection switch: frequency conversion and power frequency interlocking, and the power frequency operation is the original control system.
Frequency conversion and power frequency conversion by the switch, and interlock protection. (2) Under the variable frequency mode - Local/Remote - Select switch: Realize the local potentiometer manual speed regulation. Inverter PID closed-loop speed control method.
(3) Variable frequency soft start: The motor is started by the inverter. The motor voltage adopts digital automatic slope compensation technology. When the motor speeds up slowly, the mechanical impact of the system is small, which can significantly prolong the service life of the electronic control element and fan machinery.
(4) It has perfect motor and inverter's own protection function: motor under voltage, regenerative over voltage, over current, overload, short circuit, overheat protection and so on.
(5) Cabinet meter display functions such as power supply voltage and motor current. Inverter running status indicator display function.
Control Box Button Operation Programming Controller Wind Inverter Blower Inverter Pump Inverter Inducer Fan Blower Pump
(6) Inverter fault alarm indication and switch quantity transmission and reset function.
3, the principle of energy-saving overview of the AC motor speed N formula is expressed as: N = 60f (1-s) / p;
(N is the motor rpm, f is the motor acceptance frequency, p is the number of motor pole pairs, s is the motor slip rate).
It can be seen that the speed of the AC motor is directly proportional to the receiving frequency, and the motor speed can be adjusted by changing the power supply frequency of the motor. The working principle of the fluid transmission equipment (pump, fan) shows that the flow (air flow) of the pump and fan is proportional to the speed; the pressure (head) of the pump and fan is proportional to the square of the speed, and the shaft power of the pump and fan is equal to the flow rate. With the product of pressure, the shaft power of the pump and fan is proportional to the third power of the rotation speed (ie proportional to the third power of the power supply frequency).
According to the above principle, it can be known that the output power of a water pump and a fan can be changed by changing the rotation speed of a water pump or a fan. For example, if the power supply frequency is reduced from 50Hz to 45Hz, then P45/P50=453/503=0.729, that is, P45=0.729P50.
(P is the motor shaft power); reduce the power supply frequency from 50Hz to 40Hz, then P40/P50=403/503=0.512,
That is, P40 = 0.512P50 (P is the motor shaft power). As shown below:
From the above, it can be seen that using the inverter to control the flow (air volume) can save a lot of power. The boiler control system is designed according to the maximum demand at the site. The blower, induced draft fan, and feed pump are all considered in accordance with the maximum operating conditions of a single device. In practical use, they have more than 90% of the time. All work under non-loaded conditions. The use of valves and automatic spool valve adjustments not only increases the system cycle pressure and throttling losses, but also results in periodic fluctuations in the entire system due to the regulation. The installation of variable frequency control systems can solve this problem once and for all. Realize automatic control and recover investment through energy saving. At the same time, the soft start function of the frequency converter and the characteristics of smooth speed regulation can realize the smooth adjustment of the system, make the system work state stable, and extend the service life of the boiler components.
Fourth, after the frequency conversion transforms the performance frequency conversion constant pressure water supply control system in the boiler application has the following function:
1. Because the pressure of the boiler to the jellyfish tube is often relatively large, the speed response of the inverter is very fast, so as to avoid the fluctuation of the water pressure during the switching process.
2, the system's program execution unit - programmable logic controller (PLC) according to the actual needs of the site for the time, amplitude and program adjustments, while ensuring the reliability of the system operation.