Power non-uniformity = Ge Xinglai (1979-) Male, Taiyuan, Shanxi, Master: (2003) 1 Introduction Current AC drive technology has been widely used in the field of locomotive traction. Commonly used drive control methods for AC drive electric locomotives are available. It is divided into frame control and axis control, frame control refers to that the traction motor on the same bogie is powered by one inverter, and the axis control refers to that different traction motors are powered by different inverters, and the axis control can be changed according to each traction motor. Moment-rotation speed characteristics enable independent control and optimal control performance, but due to the large number of converters required and the high price of converters, the application is also limited. At present, the frame control mode is used more often. An inverter supplies power to multiple parallel asynchronous traction motors.Under ideal conditions, the load distribution of traction motors is the same, and the power of each motor should also be the same, but in actual engineering applications, the power deviation of parallel motors often occurs. Analysis of the reasons for its appearance is of great significance to the development of new AC transmission locomotives in China and the maintenance of locomotives.
2 Proposals In order to concretely realize the leap-forward development of the railway, the Ministry of Railways proposed that the Datong-Qinhuangdao line will be the first to achieve 200 million tons of cargo in 2005, and carried out a 10,000-ton shipment at the Daqin line from July 21 to July 27, 2003. Train traction and braking tests. The author participated in the traction performance test of locomotives. Two DJi AC drive electric locomotives were used for the reconnection operation and 120 coal trains were towed. During the test, it was found that the power distribution of the two motors running in parallel with the bogie was unbalanced, especially in the power distribution of the B-section locomotives 1 and 2 of the heavy-duty vehicle. The specific situation is that the power of motor 1 is less than the power of motor 2 during traction; and the power of motor 1 is greater than the power of motor 2 during regenerative braking; the load of the locomotive is smaller when running on a straight road or a slightly downgrade line. At this time, there was a traction condition with the bogie motor, and one was in a regenerative condition.
Shown is the total active power diagram of motor 1 and 2 during the entire line operation, from which the above problems can be clearly found. Analysis of active power diagrams shows that the overall trend of power change is basically the same throughout the entire process. When traction, the power of motor 2 is about 25% larger than that of motor 1. In regenerative braking, the power of motor 2 is about 25% smaller than that of motor 1. This shows that the motor characteristics are basically the same.
DJi heavy-duty car B end 1, 2 motor power unevenness map for the locomotive from the start to run at a speed of 75km/h when the - segment power deviation scatter plot, the calculation method for the motor 1 power a motor 2 power motor 1 power + Motor's ten-power/negative slip is too small. Its electromagnetic rotation is also biased at synchronous angular velocity; f, is the power factor of the rotor; it is the rotor current converted value.
Very small, X At this time, the X. term and the (Rr/S) term can also be seen from the middle, after entering the permanent power area, the power deviation of the two motors is about 25%. Based on the above data processing results, consider that power deviation may be caused by wheel diameter deviation.
Table 1 shows the wheel diameter values ​​measured during the test. The test method is to take 10 laps for each wheel to obtain the average value.
Table 1 Wheel diameter table Wheel diameter /mm The end of the locomotive B end heavy-duty truck B end 3 Theoretical analysis 31 Influence of wheel diameter deviation from the motor characteristics The design of the asynchronous traction motor is based on the locomotive unique and strongly changing load status. As a basic premise, the locomotive's operation map is transformed into the torque-rotation characteristic of the motor.
The speed-torque characteristics of AC asynchronous traction motor are shown as the torque-to-slip characteristic curve of asynchronous traction motor. In the figure, when S is in the range of (0,1), the motor is in traction mode; S3.2 is the average torque deviation. The relationship between the wheel diameter AC asynchronous traction motor equivalent circuit is known from the equivalent circuit diagram of the asynchronous motor (), the electromagnetic power through the air gap into the rotor is the pole pair; J (Rr / S) 2 ten (1) 2 in the AC drive In the traction control system, since the slip S is generally ignored, therefore, the cos T2 is called and the torque formula can be written as same as for the rotor current/2. When S is small, (w) 2 items can be ignored, so if UiEi is considered that the relationship between torque and frequency can be expressed as Ui * motor stator terminal voltage; * asynchronous motor slip frequency; fs asynchronous motor stator frequency.
If the characteristics of the bogie motor are the same, only the wheel diameter deviation is taken into account. Due to the same locomotive wheel speed, the mean torque deviation table corresponding to different slip ratios in Table 2 is the average torque deviation/% conversion form. =(:+:/2) is the average torque deviation.
From Equation (8), it can be seen that the average torque deviation can be obtained by knowing the wheel diameter of the two wheels and the slip ratio of one of the traction motors.
It is known that the efficiency of Di=machine is 95%, and the slip rate of the motor is not known. Now the slip ratio is taken into equation (8) for calculation. As can be seen from Table 2, the power unevenness is about 25%. It is estimated that the traction asynchronous motor slip rate of the DJi AC drive electric locomotive is about 1.2%.
Because the synchronous angular velocity is the same, the power imbalance is equivalent to the torque imbalance. As can be seen from Table 2, with the increase of the slip ratio, the imbalance of the torque distribution caused by the wheel diameter deviation can be alleviated, but the excessive slip rate makes As the copper consumption of the rotor increases, the temperature rise of the rotor increases, and the efficiency of the motor decreases. From the perspective of reducing the loss or increasing the thermal efficiency of the motor, it is desired to reduce the slip rate. Therefore, the rated slip of the motor should be based on various conditions. Considering.
3 Conclusions For electric locomotives running in parallel with multiple motors powered by one inverter, motor characteristics or wheel diameters are different, which will cause the motor load to be unevenly distributed, the larger the characteristic or wheel diameter deviation, and the uneven load condition. To be serious, some motor currents are large, and some motor currents are small.
This not only makes it easy to overheat individual motors and causes idling, but also significantly reduces the average output torque of the locomotive. Therefore, in actual applications, in addition to making the same characteristics of the motor under the same bogie, torque imbalance factors caused by wheel diameter deviation should also be taken into consideration, and the rated slip rate of the motor should be selected.
Absorbent Sticy Floor Gurad,Blue Plastic Floor Protector,Floor Protection Rug,Clear Floor Protector
Suzhou Surface Protective New Material Technology Co.,Ltd , https://www.surfaceprotective.com