A user profile
Shandong Junlin Group Co., Ltd. is one of the top 100 enterprise groups in Shandong Province. It has an annual output of 100,000 tons of jungle aluminum, 150,000 tons of jungle bulbs, 15,000 tons of jungle pipe fittings, 39,000 kilowatts of installed jungle thermal power, 9 million square meters of jungle tape, 2.3 million meters of Jungle hoses, 30,000 sets of body parts, 5000 jungle cars, 20,000 industrial sewing machines, 6 million tons of jungle cement, jungle machinery, jungle sewing, and jungle auto parts, and 18 companies. The center and the only industrial aluminum research and development center in Shandong Province. All companies have passed the ISO9001-2000 quality system certification and the British crown international quality system certification, including jungle aluminum, jungle tube, jungle tape, jungle machinery, the jungle Chinese and German cars for the provincial high-tech enterprises.
Second, high-voltage inverter speed energy-saving principle
High-voltage frequency conversion speed regulation is through changing the power frequency input to the AC motor, so as to achieve the purpose of adjusting the speed of the AC motor. According to the principle of electrical machinery, AC asynchronous motor speed is determined by the following formula:
n=60f(1-S)/p (1)
Where: n - motor speed;
F—input power frequency;
S—motor slip;
P—motor pole pair number.
According to equation (1), the output speed of the motor is related to the input power frequency, slip rate, and the number of pole pairs of the motor. The direct speed regulation method of AC motor mainly includes:
1) Pole-changing speed regulation (adjustment p);
2) Rotor series resistor speed regulation; (only for winding rotor motor)
n=60f(1-S)/p (1)
Where: n - motor speed;
F—input power frequency;
S—motor slip;
P—motor pole pair number.
According to equation (1), the output speed of the motor is related to the input power frequency, slip rate, and the number of pole pairs of the motor. The direct speed regulation method of AC motor mainly includes:
1) Pole-changing speed regulation (adjustment p);
2) Rotor series resistor speed regulation; (only for winding rotor motor)
3) Cascade speed regulation or internal feedback motor (adjustment S); (only for rotor motor)
4) Fluid coupling speed control;
5) Frequency control (adjustment f);
Among them, the advantages of high-voltage frequency conversion are the most, and they have been widely used.
5) Frequency control (adjustment f);
Among them, the advantages of high-voltage frequency conversion are the most, and they have been widely used.
Blade-type fan (or water pump) equipment is a square-torque type load, and it satisfies the three similar laws of fluid mechanics (that is, similar geometry, similar motion, and similar dynamics), and its rotational speed n, flow Q, and pressure ( Head H) and shaft power P have the following relationship:
Q1/Q2=n1/n2 (1)
H1/H2=(n1/n2)2 (2)
P1/P2=(n1/n2)3 (3)
In the formula: Q1, H1, P1—Flow, pressure (or lift), shaft power of fan (or water pump) at n1 speed;
Q2, H2, P2—Flow, pressure (or lift), and shaft power for a fan (or water pump) under similar operating conditions at n2 speed.
According to equations (1), (2) and (3), the flow rate of a fan (or water pump) is proportional to its rotation speed, and the pressure (or head) is proportional to the square of its rotation speed, and the shaft power is proportional to the cube of its rotation speed. When the fan speed is reduced, its shaft power decreases with the third power of the speed, and the electric power required to drive the fan's motor can be reduced accordingly.
Q1/Q2=n1/n2 (1)
H1/H2=(n1/n2)2 (2)
P1/P2=(n1/n2)3 (3)
In the formula: Q1, H1, P1—Flow, pressure (or lift), shaft power of fan (or water pump) at n1 speed;
Q2, H2, P2—Flow, pressure (or lift), and shaft power for a fan (or water pump) under similar operating conditions at n2 speed.
According to equations (1), (2) and (3), the flow rate of a fan (or water pump) is proportional to its rotation speed, and the pressure (or head) is proportional to the square of its rotation speed, and the shaft power is proportional to the cube of its rotation speed. When the fan speed is reduced, its shaft power decreases with the third power of the speed, and the electric power required to drive the fan's motor can be reduced accordingly.
From the above analysis we can see that speed regulation is an important way for pump energy saving. The use of high-voltage frequency control can achieve linear adjustment of the pump motor speed, by changing the motor speed to adjust the pipeline pressure and water supply.
Third, the project overview
Longkou Thermal Power Plant is a private power plant under the jurisdiction of the Jungle Group and is a comprehensive utilization enterprise of combined heat and power. It has an installed capacity of 39,000 kW, an annual generating capacity of 298 million kW, and an annual heating capacity of 4.62 million gigajoules.
Longkou Junlin Power Plant newly installed two 7.5 MW generating units in 2010. Each unit boiler was equipped with a 1000 kW induced draft fan and a 400 kW secondary fan. Three 1000kW boiler feed pumps (shared by two boilers). A total of 5 sets of induced draft fan, secondary fan and a feed pump are controlled by the CL2700 high-voltage frequency converter manufactured by Shenzhen Kelu Inverter Co., Ltd. to control the air volume or flow rate.
IV. Project implementation plan
In order to prevent the influence of frequency converter inspection or failure on the operation of the water supply system, the five sets of high-voltage variable frequency speed control systems provided by Shenzhen Kelu Inverter Co., Ltd. are equipped with manual power frequency bypass cabinets. The specific bypass implementation mode is shown in the following figure:
The principle of one-time wiring using the “one-on-one†manual bypass scheme is as follows:
CL2700 high-voltage variable frequency speed control system with a manual power frequency bypass system diagram
When the user switch QF1 is closed, the motor realizes variable frequency or power frequency operation. When the high-voltage power supply is connected to the high-voltage inverter through the high-voltage isolation switch QS1, the inverter output is sent to the motor through the high-voltage isolation switch QS3, and the motor runs in variable frequency; the high-voltage power supply can also directly start the motor through the high-voltage isolation switch QS2, and the motor runs at the power frequency. The high-voltage isolation switches QS2, QS3 are mechanically interlocked to ensure that the power frequency circuit and the frequency conversion circuit do not conduct at the same time. When the frequency converter is overhauled, QS1 and QS3 are disconnected, and QS2 is closed so that the motor frequency is running without stopping. QS1 and QS3 form a distinct disconnection point to ensure the safety of maintenance personnel.
Manually bypassed bypass cabinets are mainly composed of isolated knife gates. In use, they can be manually switched between variable frequency operation and power frequency operation. During the overhaul of the high-voltage frequency converter, the bypass isolation barrier closes the high voltage motor directly from the grid to provide high-voltage power without affecting the user's use; while the inverter isolation barrier has a clear physical breakpoint, which can protect the maintenance personnel. Safety. There is a mechanical interlock between the bypass isolation barrier and the inverter isolation barrier, which ensures that the power frequency loop and the inverter loop will not be turned on at the same time.
Two control methods: Local and remote DCS control can be performed.
Five sets of high-voltage variable-frequency speed control systems are consistent with the DCS interfaces. The specific interfaces are as follows:
The interface between DCS and frequency converter is as follows:
1. Converter to DCS:
System Ready (Switch)
Inverter alarm (switch quantity)
Inverter fault (switch quantity)
Local/Remote (Switch)
Run/stop status (switch quantity, feedback inverter status)
Frequency / power frequency status (switch)
Emergency stop (switch)
Current running current of the inverter (analog, 4~20MA)
Inverter output current (analog, 4~20MA)
2. DCS to frequency converter:
Frequency start/stop (switch)
Fault reset (switch quantity)
Frequency given (analog, 4~20MA)
V. Project economic benefits
Longkou started to install and commission five high-voltage variable-frequency speed control systems from Linfen Thermal Power Plant in mid-May 2010. Shenzhen Kelu Inverter Co., Ltd. arranged professional and technical personnel to guide installation and commissioning on site. Five sets of high-voltage variable-frequency variable-speed control systems were installed and adjusted to normal. Put into operation, it takes only half a month. Both local/remote DCS can be flexibly controlled, stable operation and normal performance. The relative power frequency throttle adjustment achieves a better power saving effect.
Sixth, other benefits:
1. Reduce the start-up shock, mechanical friction and vibration of the pump and extend the service life of the unit.
When the motor is directly started, the starting current is usually 4-7 times of the rated current, and the starting current is large. Frequent starting will easily damage the motor. With frequency conversion speed regulation, the motor speed will increase smoothly during the start-up process, the current will be steady, and there will be no impact current. It is the most perfect. Soft start
2. Reduced operating noise of fans and pumps and improved working environment
3, CL2700 high-voltage variable frequency speed control system system protection function, reliable operation, with undervoltage, overcurrent, overload, overheating, lack of phase, short circuit protection and other functions, the motor plays a very good protection.