Inverter regenerative braking application - Solutions - Huaqiang

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A chemical fiber filament drawing production line consists of three drafting machines, each driven by three motors. One roller motor power 22KW, 4 pole, worm reducer, speed ratio is 25:1; two-roll motor power 37KW, 4 pole, worm reducer, speed ratio 16:1; three-roll motor power 45KW, cylindrical gear reduction The speed ratio is 6:1. The motors are driven by Huawei TD2000-22KW three-inch IHF37K and 45K inverters. The three inverters are proportionally controlled according to the draft ratio and speed ratio. Its working process is as follows: the tow is wound on one roll, two rolls, three rolls, and the tow is drafted by the frequency converter controlling the different speeds between the three rolls. #p#分页头#e#

When driving, the drafting ratio is small, the total length of the tow is low, and the system is driving normally. After being put into production for a period of time, due to the process adjustment, the draft ratio and the total denier of the tow are increased. (The draft ratio is determined by the process. Generally speaking, the thickness and the number of the tow are higher. The thicker the tow, the larger the drafting ratio or the total denier, the greater the drag force of the three rolls to the two rolls and one roll.) At this time, a problem arises. The driving time is not long, and one-roller frequency converter frequently displays SC (overvoltage prevention).

Occasionally, this phenomenon occurs in two-roller inverters. The time is a little longer, one roll inverter protection stops, and the fault shows E006 (overvoltage). Through careful analysis of the fault phenomenon, the following conclusions are drawn: since the drafting ratio between one roller and two rollers accounts for 70% of the total drafting ratio, and the power of the two-roller and the three-roller motor is greater than one roller, The roller motor actually works in the power generation state, and it must generate enough braking torque to ensure the drafting multiple. The two rollers work between the electric and braking states depending on the process conditions, and only three rollers are electrically operated.

That is to say, if a roller inverter cannot process the regenerative energy generated by the motor, it will not generate enough braking torque, and then it will be “drag” by the two rollers. The main reason for being “dragned” is the function of the inverter to automatically increase the output frequency to prevent overvoltage tripping (ie “SC” stall prevention function).

In order to reduce the regenerative energy, the inverter will automatically increase the motor speed and try to reduce the regenerative voltage. However, because the regenerative energy is too high, the overvoltage cannot be prevented. Therefore, the focus of the problem is that it is necessary to ensure that one roller and two roller motors have sufficient braking torque. Adding one roll, two roll motor and inverter capacity can achieve this purpose, but this is obviously uneconomical. The overvoltage generated by one roller and two rollers is disposed in time, and the DC voltage of the inverter is not increased, and sufficient braking torque can be provided.

Since this is not taken into account in the design of the system, it is not possible to use a common DC bus absorption type or energy feedback type. It has been carefully demonstrated that only one set of external brake units can be added to each of the one-roll and two-roll inverters. Two sets of Huawei TDB-4C01-0300 brake components were selected for calculation. After driving, the braking force of the two groups of braking units, especially the one-roll braking resistor, is very high, indicating that our analysis is correct. The entire system has been in operation for nearly a year and no overvoltage has ever occurred.

In this paper, the various reasons for the overvoltage generated by the inverter and the corresponding preventive measures are described in detail. Several ways of regenerative braking are discussed. The application of the overvoltage and the application of regenerative braking are carefully analyzed through application examples. The results prove that the regenerative braking function is the most important method to solve the overvoltage phenomenon.