Dec 09, 2020
The extruder is an industrial equipment with a complicated structure and complicated technical bearings. As a leading brand in the field of inverters, inverters have been committed to deep research in the field of inverters for many years! Now what we have to think about is what role the frequency converter can play in the application process of the extruder?
Many materials such as clay, food, metal, plastic, etc. can be extruded. The most common extruder is a screw extruder. Not long ago, most of the extruders were driven by DC motors, but recently, AC speed regulation is used more and more. Compared with DC speed regulation, AC speed regulation has many advantages and the cost is very competitive. Extruder is the basic equipment of plastic industry and chemical fiber industry.
1. Working principle of screw extruder
To understand the application principle of the frequency converter, we must first understand the working principle of the screw extruder! The solid particle raw material is first fed from the hopper, and then heated to plasticize or melt. The screw rotates to push the melted colloidal raw material to the exit of the extruder. The exit of the extruder is equipped with a specific die, which determines the shape of the final product. . Products such as plastic film, plastic pipe, profile and chemical fiber can all be produced by extruder.
The most common screw extruder is a single-screw extruder with a typical screw speed of 100 revolutions per minute; a twin-screw extruder is used for products that need to be mixed and extruded with two raw materials. The typical high-speed twin-screw extruder has a speed of 200 -500 revolutions per minute. The low-speed twin-screw extruder used for profile extrusion usually rotates at 10-40 revolutions per minute.
2. AC drive method
The AC drive method is actually not difficult, it is closely related to the working principle of the inverter! Only a few years ago, AC drives could not provide the excellent performance of DC drives, and the price was very expensive. However, with the rapid development of power electronic devices and microprocessor technology in recent years, the introduction of AC control theory and the concrete improvement of actual AC control software, AC drive technology has a better cost-effectiveness than DC drive in many application fields. The current FC302 series inverter used in the extruder has better speed control performance and torque response speed than DC drives. The open loop speed control accuracy is better than 0.5%, and the closed loop speed control accuracy is better than 0.1%.
The starting torque of the extruder may reach 200%-250% of the operating torque, which is higher than the maximum 180% starting torque of the FC300 series inverter. Therefore, a larger driver is required, but the equipment can also be operated at the rated speed The solution is in the constant power area of the AC motor, because the load torque of the extruder at full speed does not require the rated torque of the motor.