VTdrive AC Drive be Used to Circular Knitting Machines

10 04,2020

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First, the scene

Commissioning machines and equipment: knitting machine

VTdrive inverter models: VT2-4T-5d5

Second, the industry introduction

Circular Knitting Machine is now widely used in the textile industry. Taiyuan Ji an industry, the market potential of the inverter is still quite large.

Third, the system solutions and system wiring

At present, Taiyuan Ji has a more mature control system, basically all using single-chip control, or PLC + man-machine interface control. Its function requirements of the inverter is very simple, only need to start and stop the terminal control, analog given frequency or multi-segment frequency given.

In the control performance, the inverter is required to provide greater low-frequency torque, because heavy load when weaving, requiring jogging response to be rapid. Here we use speed sensorless vector control mode inverter to improve motor speed accuracy and low frequency torque output.

Great circular machine requires absolute prohibition of motor reversal and rotation phenomenon, or needle bed needle will be bent or even broken. For the large circular machine system with one-way bearing, the influence in this respect can not be taken into consideration. If the positive and negative rotation of the system completely depends on the motor control, we should pay attention to the appropriate DC braking function.

In speed control, the system is required to run at least three speeds. First, jogging operation, the frequency of about 5-6Hz; Second, the normal high-speed weaving operation, the maximum frequency up to 80Hz; Third, the low-speed close cloth operation, when the cloth woven to a certain length, cloth. For multi-speed control, there are basically two kinds of control schemes. A program is to use analog given frequency, whether it is jogging or high-speed low-speed operation, analog signals and operating instructions given by the control system; the other program is to use the frequency converter comes with multi-band frequency, the control system Multi-frequency switching signal is given, while jogging is provided by the inverter's own jogging function. The setting frequency for high-speed weaving is given by analog quantity or frequency converter open-loop frequency.

Great circular machine application

Fourth, debugging steps

◆ According to the motor nameplate, set the motor parameters, after the large circular machine run in for some time, the maximum frequency can be gradually increased to 80Hz.

P3.03, Pd.09, Pd.14 These settings are designed to improve the dynamics of the starting and stopping moments of the big circular machine. Great circular machine response to start faster, low-frequency torque output, and downtime to be smooth, soft, in order to protect the equipment needle bed. Therefore, the starting frequency is reduced to 0.2Hz and the vector control pre-excitation time is reduced to 0.1S. At the same time, the S-curve time is added to 0.5 to ensure the smoothness of the frequency adjustment from start to stop, and then the braking torque is reduced to 50%. After repeated experiments, the group of parameters to achieve a good control performance.

Pd.01, Pd.03 and Pd.05 These function codes are designed to improve the vibration problem of the big circular machine at high speed, increase the ASR switching frequency and reduce the proportional gain of the speed loop, so as to reduce the torque of the inverter at high speed Output, reduce motor jitter, thereby improving the entire machine in the high-speed operation of the violent vibration problems.

Pd.33 is designed to reduce the output current during constant power operation

Fifth, on-site debugging problems to solve

◆ control mode of operation should be vector control 1 or vector control 2?

Large circular machine for the control performance of the inverter half not high, the use of vector control 1 should be able to meet the requirements, the use of VTdrive  speed sensorless vector control inverter can better improve the large low-frequency large torque machine torque output and Steady speed performance, especially low-frequency torque output characteristics, the effect is good.

However, during on-site commissioning, it has been found that when the vector control 2 mode is started with the DC braking function, the slewing phenomenon can be eliminated or improved a lot. Therefore, all the large circular machines for on-site debugging adopt the vector control 2 modes.

◆ start and stop the moment the motor shaft has a slight rotation

For machines with a one-way bearing on a large circular machine, the effect of this slight rotation can be completely ignored, but some large circular machines, which are not mechanically forbidden to be reversed, need to be taken seriously when fully controlled by a motor. Because of slight reversal may damage the dial.

Here, you need to set the stop DC braking parameters, to ensure that the use of DC braking when stopping the motor shaft inertia completely brake, but also ensure that the starting point of the motor shaft angle and PWM waves issued by the angle to solve the start Instant motor shaft rotation problem.

P3.05 = 2, P3.06 = 2, P3.07 = 120, P3.08 = 0.5. When it is down, it will start with 120% inverter rated current and DC braking will be started at 0.5Hz, lasting braking time will be 2s.

After setting the DC braking function, basically the motor shaft rotation start-stop moment can be reduced to a minimum, the final effect than the original supporting the other foreign brands inverter actual effect is good.

Sixth, sum up:

At present, VT2 vector control vector inverter, is obviously more than enough performance on the big circle of more than enough. Cost-effective competitive advantage is obvious.

In addition VTdrive can also be customized to help users reduce costs. For example: Taiyuan Ji has a complete set of mature control system, the more advanced control systems are basically touch screen + PLC control, just PLC controller cost is relatively high. VTdrive inverter can be combined with touch screen and other man-machine interface, the use of 485 communication control, developed a large circular machine control system industry, that is man-machine interface + Taiyuan Ji industry-specific inverter, eliminating the need for intermediate PLC link , Can greatly reduce the cost of large circular machine system.