1) Function of magnetic slot wedge
The mechanism of magnetic slot wedge improving motor performance is mainly realized by improving the magnetic density distribution and amplitude of air gap. Magnetic slot wedge can improve the magnetic density distribution of air gap and reduce pulsation, so as to improve efficiency, reduce iron loss and reduce temperature rise.
2) Requirements for magnetic slot wedge
Laminated magnetic slot wedge is mainly composed of glass fiber cloth, epoxy resin, iron powder and other additives. There are many kinds of magnetic slot wedges, such as magnetic slot mud, molded magnetic slot wedge, pull-out magnetic slot wedge and laminated magnetic slot wedge. The characteristics of magnetic tank mud are easy to use and high relative permeability. Its disadvantages are difficult to ensure the consistency of quality and low strength, especially at high temperature. This is unfavorable for motors using VPI process. Molded magnetic slot wedge has balanced magnetic and mechanical properties, but it is special for special mold, low production efficiency and high cost. The pull-out magnetic slot wedge uses iron wire, and the mechanical properties of the material are anisotropic. If the iron wire falls off, it will bring hidden dangers to the operation safety of the motor. The dimensional accuracy of molded magnetic slot wedge and drawn magnetic slot wedge depends on the accuracy of the die, and the reprocessing performance is poor. Compared with the above magnetic slot wedge, the laminated magnetic slot wedge has good comprehensive performance, such as high production efficiency, low cost, high mechanical strength, moderate magnetic properties and good machining performance. Most foreign manufacturers produce laminated magnetic slot wedge.
3) Mechanical property requirements of magnetic slot wedge
The magnetic slot wedge bears various forces during assembly and operation. During operation, the interaction force between the magnetic field in the tooth area and the current in the magnetic slot wedge (the volume resistance of the magnetic slot wedge is required to be high), the magnetic tension between the magnetic field in the tooth area and the magnetic slot wedge, and the force transmitted by the mechanical vibration of the core tooth to the magnetic slot wedge. During assembly, the magnetic slot wedge will be impacted due to the matching of dimensional tolerance; In addition, iron powder and resin are required to have sufficient bonding strength. This requires that the magnetic slot wedge should have sufficient bending strength, modulus, bonding strength and impact toughness.
4) Requirements for temperature resistance of magnetic slot wedge
With the development of motor technology, the temperature resistance grade is higher and higher, and the working condition is worse, which has higher requirements for magnetic slot wedge; In addition, new motor manufacturing processes such as VPI also have strict requirements on the temperature resistance of magnetic slot wedge. These require that the magnetic slot wedge has high temperature heat resistance and high temperature stability.
5) Requirements for magnetic properties of magnetic slot wedges
The magnetic slot wedge shall have appropriate magnetic properties, i.e. appropriate relative permeability. If the relative permeability is too high, the magnetic flux leakage will increase and the torque will decrease; On the contrary, the relative permeability is too low, and the effect of magnetic conduction slot wedge on improving motor efficiency, reducing temperature rise, noise and vibration is not obvious.