With the continuous advancement and development of the manufacturing industry, in order to improve production efficiency, the power level of production machinery and equipment is gradually increasing, so that multiple motors of the same specification are required to synchronously drive high-power mechanical equipment, and one inverter drives multiple units in parallel. When the motor is found, even if the maximum power inverter is used, the demand cannot be met. Therefore, it is necessary to adopt a master-multi-slave mode, that is, each inverter drives one motor, and each motor is synchronized by a master multi-slave mode.
The following is the application of a field mixer. Our inverter adopts a master-three-slave mode to control the synchronous operation of four motors to achieve the stirring function. The power part of the mixer is composed of four motors. The structure is as shown in the figure: Motor M1 M2 is coaxial rigid; M3 and M4 are coaxial rigid connections; M1 and M3, M2 and M4 have synchronous gear rigid connection (that is, two rigid connections between four motors, driving one of the other three motors can be linked).
Because the four motors are rigidly connected, the synchronization control of the inverter is extremely high. If one of the motors is not synchronized, it will cause damage and abnormal noise to the mechanical bearing structure. In order to achieve high-precision synchronous control, combined with customer needs. Our company has made a "power balance" drive solution to make the drive effect perfect.
The power balance scheme has extremely high requirements on the control performance of the inverter. Pay attention to the following points:
1. "Power balance" as the name suggests is to ensure that the output power of each inverter drive motor is equal, thus eliminating the torque between the motors, no abnormal noise, and perfect control. This process requires the inverter response algorithm to be fast, accurate and precise.
2. In order to realize fast information exchange between four inverters, our company uses CAN card for communication, combined with CAN bus communication speed, stable performance, strong anti-interference ability, perfect application in power balance scheme, thereby ensuring the reliability of the solution.
3. The specific way to realize this kind of scheme is as follows: one of them is defined as the master, the remaining three are slaves, and the master and the slave are connected by CAN card communication. The running frequency of the slave is equal to the host plus PID adjustment (f from =f Main +PID);
4. PID regulation detects the difference between the active current of the master and the active current of the slave through CAN communication, realizing the automatic adjustment of the output frequency of each slave, so that the output power of each of the four motors is the same at every moment, ensuring the reliability of the drive.
5. At present, the power balance is a master-slave mode, and the master and slave running speed modes are adopted. In the case where there is a need for a higher response in the future, the host running speed mode and the slave running torque mode can be adopted;
The power balance realizes high-precision synchronous driving of multiple motors, and also needs to implement strict protection schemes for inverters and machinery, such as the following schemes:
1. When the host fails, the host will send a free stop command to each slave;
2. When one of the slaves fails, the failed slave sends a free stop command to the master, and the master then sends a free stop signal to the other slaves;
3. In order to avoid damage to the mixing arm by free parking, the deceleration stop mode is adopted to allow each inverter to stop working at the same time, thus ensuring the integrity of the machine.
4. It is this strict protection mechanism that not only ensures the high-reliability operation of the inverter, but also minimizes the mechanical loss when the inverter fails, so that each customer can highly recognize the products of VEICHI and solutions!
At present, our inverter "one master and multiple slaves" program is very mature, and has used many occasions, such as: coal belt conveyor, food belt conveyor, gravel belt conveyor, mixer, pulverizer, etc., with the continuous development and progress of the industry, “one master and more” will become a trend in the future. VEICHI will provide better technical solutions for the industrial control industry before the trend. At present, our company is mature and perfect, and the future will be more perfect, because VEICHI is constantly making breakthroughs and progress!