# Insertion Performance Study of an Inductive Weft Insertion System for Wide Weaving Machines
## 2 Weft Insertion System Structure and Operating Principles  
The weft insertion system can be divided into three parts: a weft insertion guideway, a permanent magnet array, and a magnetic levitation shuttle (hereinafter referred to as the shuttle). The three-dimensional structure is illustrated in Figure 1a. The weft insertion guideway is installed below the lower warp, with two permanent magnet arrays mounted on either side of it. The shuttle is suspended above the weft insertion guideway and permanent magnet arrays, positioned at an angle between the upper and lower warps. The weft insertion guideway consists of an iron core made from stacked silicon steel sheets and electromagnetic traction coils. The electromagnetic traction coils are wound in a short distance double-layer stacking (i.e., \"half-filled slot\") fashion on the teeth of the iron core, forming three groups of windings. In the winding connection scheme shown in Figure 0(b), S represents the number of slots on the iron core of the weft insertion guideway. Each coil of the winding spans two iron core slots, with the center of two adjacent magnetic poles spanning three iron core slots. The slot-tooth pitch is 60\({}^{\circ}\) in the electrical angle. Figure 0(c) depicts the schematic structure of the shuttle shown in Figure 0(a). The shuttle consists of a conductive plate, high-temperature superconductor, and a fixed plate. The conductive plate is embedded beneath the shuttle, with its lower surface parallel to the lower surface of the fixed plate. At the tail of the shuttle, there is a selvedge device designed to clamp and guide the weft yarn during insertion. Inside the shuttle, there are cavities on each side of the conductive plate, intended for securing the high-temperature superconductor and containing liquid nitrogen.  
When a suitable symmetrical three-phase alternating current is applied to the electromagnetic coil windings, a traveling magnetic field is generated in the gap between the warp insertion guideway and the suspended shuttle. This results in the induction of eddy currents in the shuttle's conductive plate. The interaction between the eddy current magnetic field and the source magnetic field of the warp insertion guideway generates traction force, thereby driving the shuttle to pull the weft yarn and achieve weft insertion.  
Simultaneously, after the superconducting material inside the shuttle's two cavities is cooled with liquid nitrogen, the change in the magnetic field induces a superconducting current within the material. Consequently, a magnetic field opposite to the external magnetic field is generated inside the superconductor, aiming to counteract the influence of the external magnetic field. Two opposing magnetic fields enable the superconductor to stably levitate above the permanent magnet arrays on both sides of the weft insertion guideway, providing levitation force equal to the weight of the shuttle and sufficient guiding force to maintain shuttle stability.  
By appropriately designing the structural dimensions of the conductive plate and changing the frequency of the input current, stable and rapid weft insertion motion can be maintained under continuously changing yarn tension and suspension height.  
Figure 1: Structure of the weft insertion system.