Air compressors provide gas sources for various dust collectors and pneumatic equipment in the cement industry and are high-power equipment. The air compressor control system adjusts the gas production amount by opening and closing the intake valve according to the amount of gas used in the field. However, when the on-site gas consumption is low, when the intake valve is closed, the air compressor is in an idling state, and there is a huge energy waste. The closed-loop control of the air compressor by the variable frequency speed control technology can effectively solve the problem of air compressor waste and power consumption, and also make the pressure of the pressure system more stable. Therefore, it is planned to carry out frequency conversion transformation of the air compressor control system during the winter maintenance period. .
1 The necessity of frequency conversion of air compressors Observe the operation status of air compressors (such as loading and running time, load shedding time), and confirm whether the air compressor has room for frequency conversion. There are 3 air compressors in the air compressor station, one is fully loaded and operated, one is regulating the gas volume, and the third is in the standby state. The air-conditioning operation air compressor cut-off point is set to 7.2 bar, and the cut-off point is set to 6.5 bar. When the exhaust pressure reaches 7.2 bar, the air-conditioning operation air compressor starts to reduce load operation and starts timing; after a delay of 120 s, If the system pressure is not lower than 6.5 bar, the air volume control air compressor automatically stops and goes into standby mode. In the actual operation, the loading running time is 34min, and the no-load running time is 70110s, so it is preliminarily determined that there is room for energy-saving transformation.
2 Reconstruction plan and implementation Air compressor frequency conversion speed control system takes pipeline pressure as the control object, and the inverter cabinet, motor and pressure sensor form a closed-loop control system.
The air compressor control system is different from the water pressure control system of the water chestnut. It is a complex control system and also involves oil circuit and gas path protection. In order to ensure the reliability and modification of the air compressor control system, the star-delta circuit is still in the main circuit. The air compressor is a star start, and it is switched to a triangle operation after the start. The frequency converter is driven by the auxiliary contact of the star-delta start switch contactor KM2. After the air compressor is started, the loading and unloading operations are started to generate compressed air. When the air compressor protects the action, the star-delta circuit is tripped, the inverter drive is lost, and the inverter is stopped. The original air compressor control system power supply takes the autonomous loop, which is AC220V. After the frequency conversion is reformed, the power supply of the air compressor variable frequency control system is taken from the main circuit breaker of the frequency conversion cabinet. Since the air compressor adopts a water cooling system, only one axial flow fan is added as a motor cooling fan for the problem of motor frequency conversion and low speed operation. There are 3 air compressors (2 sets of operation and 1 set of hot standby) in the air compressor station. Therefore, the power frequency and frequency conversion of the control system are no longer considered during the transformation. In this transformation, the inverter uses the ABBACS800 series of inverters. The air compressor variable frequency control main circuit is as shown.
Air compressor change é“Ž control main circuit air compressor frequency conversion retrofitting leftover problem After the inverter power-on setting parameters, start the air compressor, the inverter shows the operation, but the air compressor control system trips, indicating that the fault is FAULTDIRECTROT (drive motor steering error). Refer to the instruction manual and give the treatment method as â€œcorrectly connect the phases of each phaseâ€. Since the motor has been turned correctly after the air compressor is rebuilt, the motor reversal problem can be basically eliminated. Then repeatedly start the air compressor 'the same fault occurs.
Read the air compressor user manual and found that the air compressor has two pressure measuring points (final compression pressure, manifold pressure) and one temperature detection point. The temperature sensing point is independent of motor steering and the pressure may be related to steering control. Observing the starting process of the air compressor, it was found that the air compressor motor did not turn in the first few seconds, causing the air compressor to trip. In the control loop, the frequency converter is driven by the auxiliary contact of the star-delta start switch contactor KM2. In the star-delta start process, before the switch, the inverter does not drive the air compressor motor, and the final compression pressure sensor of the air compressor does not detect the pressure, so the air compressor control system considers that the motor is turning incorrectly. Based on the above judgment, the drive point of the inverter is replaced with the auxiliary contact of the first contactor KM of the star-delta, and the inverter is started at the same time as the air compressor is started. After the transformation is completed, the air compressor is restarted successfully. The star-delta start diagram is shown.
Before the frequency conversion transformation, the operating states of the two operating air compressors can be interchanged. After the frequency conversion, if the cut-off point of the first air compressor is set lower (higher than the air compressor of the variable frequency operation), the first air compressor will be caused when the system pressure fluctuation reaches the cut-off value (should be completely Loading and running) adjusts the gas volume operation, while the variable frequency speed control air compressor is always loaded and running, thus losing the meaning of the frequency conversion transformation. Turn the cutoff point of the first air compressor up (down to page 77) Electrician*|2013ä¸¨Technical exchange is known, under the correct wiring, when the earth 161 turns to run the broken llOkVI mother transmission, UOkVI mother TV The secondary voltages A, B, C; ji are normal, the phase sequence is correct; when the Tuqiao station takes the earth 161 from the run to standby, it will take the earth 162 turn operation to the llOkV mother power transmission, llOkV mother TV secondary voltage A The B and C phases are normal and the phase sequence is correct.
If the A phase of the east line of the earth is opposite to the west line C of the earth, then: (1) When the earth is running at 161 rpm, the secondary voltages of the UOkVI mother TV are normal, and the phase A of the east line is taken. After taking the C phase of the Tuxi 162, the UOkVI mother TV secondary voltage A phase is zero; since the eastward TV of the earth is just connected to the A phase, the secondary voltage is also zero.
(2) When the earth dong 161 is transferred from the operation to the standby, it will take 162 rpm to run the earth, the secondary voltage A and B phases of the llOkV mother TV are normal, and the phase C of the west line of the earth is connected to the phase A of the earth 161. Then, the llOkV mother TV secondary voltage C phase is zero; since the west line TV is connected to the A phase, the secondary voltage is normal.
2.3 After the process of operation is in question, there is no abnormality in the TV equipment in the station, and the possibility of the TV itself is temporarily excluded. Check out the joints of the soil and east line cable in the station, and at the same time, let the Tuqiao station take the Tuxi 162 from the operation to the standby, and then transfer the Tuqiao station Jintudong 164 to the Tuqiao station llOkV mother transmission, and found that the llOkV mother TV The secondary voltage is normal and the phase sequence is correct. Let the soil bridge llOkV bust 112 run to the earth bridge llOkVI mother power, check llOkVI mother TV secondary voltage normal, phase sequence is correct. At this point, the possibility of the TV itself can be completely eliminated. After the inspection, it was found that the A phase of the HkV eastbound line and the west phase of the westward line C were connected to the side of the Tuqiao station, so the application of the llOkV to the east and west line was transferred for inspection and treatment.
3 Problems When there are many abnormal situations in the new investment substation, the dispatcher must analyze the problem according to the operation of the power grid at that time, and should not blindly identify the fault point by changing the operation mode of the power grid.
3.1 The first hypothesis is that after the 1600-turn operation of Tudong Station in Tuqiao Station, the Tuqiao Station will be moved to the west 162 rpm. At this time, the UOkVI mother and mother TV secondary voltages are normal, so that the bus TV can be determined. There is no problem with the body, but it can't be found that the TV secondary voltage (the phase zero is zero) when the earth 162 is separately sent to the llOkV mother. When the earth 161 and the earth 162 are in the running state, the bus coupler 112 When the loop is running, it will lead to the connection of phase A and phase C of the east line of the earth, and the phase A and phase C of the west line of the earth will be connected, causing the phase-to-phase short circuit of the earth-to-earth line to trip on both sides.
3.2 The second assumption is that when the earth is running at 161 rpm, it is found that the voltage of the llOkVI mother A phase is zero. A conventional idea is to turn the mother unit 112 to run. If the secondary voltage of the liokvn mother TV is normal, the situation of the disconnection of the llOkV east line can be ruled out, and the possibility of the liokvi mother TV failure can be inferred. If the secondary voltage of the liokvn mother TV is also zero phase A, it can be inferred that the phase A of the llOkV eastbound line has the possibility of disconnection.
Now assume another way of reversing, that is, where the earth and earth lines are reversed, it is in the line switch to the bus section, as shown. If the mother unit 112 is turned according to the conventional idea at this time, the A phase and the C phase of the east line of the earth will be connected, causing the phase difference between the east lines of the earth to cause the switch to trip.
Another hypothesis of the mother-in-law 112 retreating from the earth and the east is the above two hypothetical situations. It is not easy to change the operation mode to find the system problem when the new investment occurs, that is, the wiring mode of the new investment system is uncertain and cannot be According to the conventional method to find faults, specific problems should be analyzed. One of the principles of the new investment is to isolate the problematic electrical part before proceeding with the new electrical part.
4 Conclusion For the new investment substation, the dispatcher must be familiar with the start-up and production plan. For the unpredictable problems in the new investment process, the dispatcher should calmly think about the root cause of the problem according to the actual situation and start the production. The plan will be adjusted in time to ensure that the mind is clear and the professional knowledge is solid, so that the work of the new investment substation should be done in a constant manner.
(Editor Yang Xiaobo) (Continued from page 47) The modified star triangle start-up diagram O.lbar can ensure that the air compressor that is fully loaded and operated is always fully loaded, and the air compressor of the frequency conversion is adjusted to run.
4Reconstruction effect One air compressor station of a company's clinker line used 5762.9023kWh before the frequency conversion transformation, and the average daily electricity consumption after the transformation was 4561.6429kW.h. The price of a frequency conversion cabinet is 110,000 yuan, and the cost can be recovered in one year. It can be seen that changing the air compressor to variable frequency operation has obvious economic and social benefits.
Electrical Engineering ä¸¨ 2013|9 177
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