Sensitivity-Based Topology Optimization of Squirrel-Cage Induction Motor in Time Domain Using Multi-Material Level-Set Method

Although the output power of an induction motor (IM) is generally lower than that of the interior permanent magnet synchronous motor, IMs are widely used in industrial world due to their solidity, low cost, self-starting, etc. For designing high-performance IMs, a computer-aided engineering approach using the finite-element method is essential. However, because a finite-element analysis of IMs takes a long time due to the long transient state in the time domain, it is difficult to perform the optimization using evolutionary algorithms. To overcome this difficulty, a sensitivity-based topology optimization (TO) method for IMs in the frequency domain was proposed. However, this method has a drawback: because the magnetic nonlinearity in the rotor and stator cores cannot be considered, the physical quantities also cannot be accurately estimated. To consider the magnetic nonlinearity in the TO of the IM, the sensitivity analysis with the rotor rotation of the IM using the time-domain adjoint variable method is proposed here. The proposed sensitivity analysis method for the steady state of the IM was evaluated, and it was applied to the TO of a squirrel-cage IM. The effective rotor structure, which is composed of the iron core and secondary conductor, was derived from the multi-material level-set method.