Performance mapping and thermal behaviour of switched reluctance machines

Switched reluctance machines are operated through unipolar currents, whose waveform (shape) is different than that of conventional AC machines. The choice of control parameters (i.e., activation angles), for precisely shaping such a current profile is thus crucial for guaranteeing appropriate performance. Indeed, equal output torque magnitudes can be achieved with differently shaped input currents, although these can result in different thermal loading and efficiency. This work analyses different control strategies for switched reluctance machines adopting a 100-kW motor as a use-case. Different operating conditions are investigated, so as to verify how varying activation angles can strongly impact on the motor’s thermal behaviour. It is demonstrated that operating points with equal power-output and very similar efficiencies can show temperature-rise differences as large as 30 K. Such a demonstration is done through a reduced-order lumped parameter thermal network, which is also exploited for extracting a temperature-rise map as a function of activation angles.