Frequency conversion energy-saving in Qinggang high-line applications - News - Global IC Trade Starts Here.

This paper is based on the frequency conversion transformation of the air-cooled line fan motor implemented by the second high-speed wire rod factory of Qingdao Iron and Steel Holding Group Co., Ltd., and deeply analyzes the benefits brought by this transformation project to the enterprise.

The air-cooled line fan of Qingsteel No. 2 High Speed ​​Wire Plant adopts centrifugal blower. Its function is to cool the coils spit out from the laying machine according to the process requirements. It delivers different air volume according to different product specifications and varieties, combined with different product specifications. Different rolling speeds corresponding to the varieties can realize different cooling rates and effects on the coils, and realize transformation of austenite to sorbite and pearlite, thereby ensuring good mechanical properties, surface quality and cold workability of the wires. The whole plant air-cooled line has 2l centrifugal blowers, and the motor power is l 0 sets 200 k W and 11 sets 132 k W. The air-cooled line fan is a centrifugal blower. Its working principle is that the motor drives the bearing box, and then the fan blades of the fan are rotated by the transmission mechanism, and the generated high-pressure wind enters the air-cooling line through the air passage to reach the hot plate on the air-cooled line roller. The purpose of the volume cooling.

1 original design air-cooled line fan problems

The following problems occurred during the operation of the air-cooled line fan originally designed by the second high-speed wire factory:

(1) due to the use of a wind deflector to adjust the air volume;

When the fan runs at full speed, the windshield has a large resistance, and a lot of energy is consumed, and no work is done;

(2) Since the 200 k W fan motor adopts soft start and cannot be started frequently, the accident rate is high and the influence time is long;

(3) The 32 k W fan motor adopts direct start, high starting current, large power consumption, and great impact on the transformer;

(4) Due to the use of the wind deflector to adjust the air volume, and the split gear adjustment, the air volume cannot be continuously adjusted, which leads to great limitations in the production of the variety steel;

(5) It takes 8 to 10 minutes to manually adjust the windshield when the variety is changed, which reduces the effective operation rate;

(6) Direct start causes mechanical vibration, and frequent fan equipment accidents cause parking. To this end, the air-cooled line fan motor is divided into two phases for non-stop production frequency conversion transformation. The first phase of the completed transformation is l0 200k W fan motor, its model is Y315L2-4, voltage is 380V.

2 Characteristics and parameter settings of frequency conversion speed regulation after transformation

The frequency conversion speed regulation is to change the synchronous speed of the rotating magnetic field by changing the power supply frequency of the stator of the motor to adjust the speed, which is an efficient speed regulation mode without additional slip loss. The key device of the variable frequency speed control system is the frequency converter, which provides the variable frequency power supply. This transformation adopts the PowerFlex400 series 22C.D460A103 inverter of AB Company. Because the fan and pump generally do not need to use the special frequency conversion motor, so the original still used. The motor reduces the cost of the retrofit and works well. The outstanding advantages of frequency conversion speed regulation are high speed regulation efficiency, high power factor on the power supply side, low starting energy consumption, wide speed regulation range, infinitely variable speed, fast dynamic response, high adjustment precision and easy operation. The design adopts AB inverter full digital LCD operation panel to be installed on the cabinet door, and is connected to the inverter through a dedicated communication cable. It can not only debug the inverter but also monitor the running status and alarm information of the inverter. The inverter starts and stops and frequency setting; in order to facilitate the operation of the on-duty personnel, a potentiometer is installed on the cabinet door to connect it with the analog input terminal of the inverter. According to the wire production process requirements of different steel grades and specifications, the frequency needs to be adjusted. The frequency setting can be completed by the digital operation panel on the frequency conversion cabinet door or by the potentiometer on it. After the second phase of the transformation, the remote operation of the operator station can be realized, and the start, stop and frequency conversion of one fan can be realized within 1 min. The schematic diagram of the system composition is shown in Figure 1 (the dotted line is the remote control system of the second phase transformation). The main parameter settings are shown in Table 1.

3 Economic Benefit Analysis 3. 1 Power Saving Effect Qinggang No. 2 High Speed ​​Wire Factory mainly produces Φ5.5mm hard wire products such as bead wire and steel cord. When rolling Φ5.5mm hard wire, the process requires 9 fans. The wind plate adjusts the air volume, and the damper has a total of 7 stops. The process requirement is to open at 4th gear, and the air volume is approximately proportional to the opening of the damper. It can be known from fluid mechanics that the air volume is proportional to the rotational speed, that is, the air volume is proportional to the frequency. Therefore, when the frequency conversion is adopted, the damper is fully opened, and the frequency of the front windshield corresponding to the transformation is about 30 Hz. Motor operating parameters before transformation: operating frequency 50H z, damper open at 4th gear, current 260 A (measured), motor power factor 0.9, the actual output power is: √3×0.38 x 260 x 0.9=1 5 4 ( k W (1) Motor operating parameters after transformation: the damper is fully open, the running frequency is 30Hz, the current is 145 A (measured), and the motor power factor is 0.9. The actual output power is: √3×0.3 8×1 4 5× 0.9= 8 6 ( k W)( 2 ) Calculated according to the operating rate of 90%, which can be obtained by equations ( 1 ) and ( 2 ). After the transformation, E t saves energy: ( 154—8 6 )×0.9×2 4×9 =13219.2 (kW•h) (3) To ensure the C-class quality accuracy of Φ5mm hard wire, the tonnage of 30# groove rolling is controlled to 300 t, and the tonnage of 28# and 29# rolling groove is controlled to 400. t, so change the tank 4-6 times a day (including daily maintenance once), each time l 5-20min, the average slot change time in 1d class is 1.33h (excluding daily maintenance). Before the transformation, it is impossible to achieve frequent starting and the failure rate is high. Therefore, when the tank is normally changed in the shift, the air-cooled line fan is not stopped; after the transformation, it can be stopped. Only this one, the energy saved per day before the transformation can be calculated from the formula (1): 154 × 1.33 × 9 = 1843.4 ( k W · h ) (4) Φ5mm hard wire of the second high-speed wire factory The products accounted for 70% of the total, excluding the other types of electricity saving, calculated according to Qingdao's current industrial electricity price of 0.6 4 ( k W·h ) (pre-tax price), 1a saving electricity: 0.64 × ( 13219 .2 + 18434 ) × 30 × 12×0.7= 242..93 (ten thousand yuan) (5) The equipment cost, cable fee and civil construction fee for the first phase of renovation are about 1.6 million yuan, so the actual investment recovery period is about 8 months. 3.2 The process optimization effect is passed. The frequency conversion can easily set the frequency to 45 Hz, but the fan damper cannot be adjusted to 6.3.

Now take only one parameter as an example (see Table 2) to illustrate the optimization of the production process in this technical transformation. It can be seen from Table 2 that the frequency can be easily set to 45 H z by frequency conversion, but the fan damper cannot be adjusted to 6.3.

4 Conclusion

In January 2009, this transformation completed a series of related work on the design of new process parameters, on-site experimental product acceptance, and process standardization for all major air-cooling processes.

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