Motor design

Good afternoon!

Today we will speak about Motor Design for our project.

A. Motor Type

In various types of motors, the axial gap structure is proven to be the most efficient way to construct a motor in limited axial space because the output torque depends on the space in the radial direction. Therefore, it is possible to obtain a high-output axial gap motor with a short axial length. In addition, the axial gap structure is suited to utilize AMM cores because it is difficult to connect AMMs to iron yokes due to their unique mechanical properties. Within the axial gap structure, there can be more than one working face from the combination of two rotors with one stator or one rotor with two stators. The combination of two rotors with one stator contributes to lower copper loss and conserves space in the axial direction. The combination of two stators with one rotor can lower the cost of magnets and yield lower iron losses on the back yoke. The number of poles and slots can be decided by taking into consideration the space for stator coils, the flux leakage from pole to a pole inside the rotor, and cogging torque.

B.  Stator Design

The geometry of a core made from AMMs is considered one of the most difficult challenges when applying AMMs to a motor. The most efficient way to use the material is to make a wound core by wrapping the AMM ribbon to form a core. However, due to the difficulty of insulating the laminated layers, eddy current is produced even though the laminated layers are perpendicular to the flux produced by the rotors. This is the main reason that the efficiency of the motor is limited. In addition, a tape-wound core needs a hollow space in the middle to keep its shape, which takes more space in a motor. In order to increase motor efficiency, a cross-section of the stator core needs to be removed to cut off the current loop in. The removal of the cross-section spawned the idea of using the removed cross-section as a core.
The 3-D core model is shown in Fig. 1. The concentrated coil is arranged outside the core, and the assembly of a coil and a core is shown in Fig. 2. There are three slots in each phase, and three phases are designed to be in a Y connection with the circuit of three coils connected in series to increase the induced voltage.

C. Rotor Design

Due to the processing difficulty of amorphous metals, variations are limited when choosing the shape of the amorphous stator cores. Therefore, stator core modifications are avoided, and more emphasis is placed on the shape of the magnets and the combination of rotors in order to decrease cogging torque. Here, skewed magnet, arc magnet, and pole shifting designs were compared with a 60◦ flat magnet design using 3-D finite element analysis (FEA) as shown in Fig. 3. The level of skewing and the arc surface angle may be selected to guarantee that a sufficient magnetic field can be produced in the stator.