Electromagnetic force is produced by the current and magnetic field in a coil, but the coil is exposed to not only the magnetic field it produces by itself but also the magnetic field from other coils and leakage flux from the core. Because of this, it is important to evaluate in advance what kinds of forces are produced in what areas due to the arrangement of the coils and the positional relationship of the coils and core using magnetic field analysis.
This analysis uses different coil positions to evaluate the Lorentz force density and electromagnetic force produced in the coils during a short circuit in order to confirm the effects that the primary and secondary coils have on each other.
Lorentz Force Density
The Lorentz force density distribution vectors of the V-phase coil as seen from the X-axis are shown in fig. 1, and the Lorentz force density distribution vectors of the three phases as seen from the Z-axis are shown in fig. 2. From fig. 1, it can be seen that the direction of the force working on the coil varies according to how the coils are wound. Fig. 2 indicates that in models A and D, in which the deviation of the Lorentz force is large, the Lorentz force density to the inside grows large because it is influenced by the adjacent coils.
From the Y-component graph, it can be seen that a greater force is working in models A and B compared to the other models. When the balance of the coil’s winding method is asymmetrical vertically, a large force is produced in the vertical direction in addition to the repulsion in the radial direction, as indicated by the Lorentz force density vectors in fig. 1. The overall force in model D is canceled out so its Y-component force is zero, but by looking at the Lorentz force density vector distribution, it can be seen that force is produced a direction that compresses the primary coil as a whole.