Modelling and Design of Halbach Array PM Excited Steel Core Outer Rotor Compulsator∗

Conventionally, railgun uses a capacitor-based source, which cannot provide the sinusoidal nature of the current. This creates a large muzzle arc due to the immediate discontinuation of the large current. This naturally leads the compulsator to be the best alternative for railgun supply. The compulsator's energy and power density are also large compared to the capacitor-based supply. Therefore, in this paper, a 10 MJ, 4-phase, 4-pole, 15000 rpm steel core stator, Halbach array permanent magnet (PM) excitation compulsator for target performance is investigated in detail. The steel core stator and air-core rotor combination are considered for the design to reduce the permanent magnet material. The PM excitation in the compulsator leads to a reduction in voluminous design and removes slip-ring arrangement. This also reduces the chance of mechanical failure. The electromagnetic analysis for specified compulsator is performed in Ansys electromagnetic suite with a magneto-static solver for excitation design and transient co-simulation with simplore for circuit discharge analysis. The mathematical modelling of the designed compulsator is also presented in detail. To design more realistic practical design factors like temperature rise, PM demagnetization effect, eddy current distribution in compensating shield, are also considered. According to results, the newly designed compulsator achieves the target objectives and is comparable to all air-core compulsator.