Skewing techniques have been widely used in the feld of the design of diferent types of electrical machines, because it can help to reduce the torque ripple, mitigate the electromagnetic noise and vibration, etc. To model the skewing efects in the electrical machine design accurately, the fnite element method is appreciated in both the academia and industry. To achieve a fast modelling of skewing efects, a novel 2D based approach to estimate the electromagnetic performances in the whole speed range for variable-speed electrical machines has been proposed in this paper, which is further improved from the traditional multi-slice method. Firstly, a series of simulations at diferent loads will be run to get the electromagnetic performances for the variable-speed machines. Secondly, based on the multi-slice method, the performance on diferent slices can be predicted from the results obtained from the existing simulations by coordinate transform and interpolation directly and no more extra simulations are needed. Thirdly, taking a ferrite magnet assisted synchronous reluctance machine (FMaSynRM) with skewing as an example, the electromagnetic performances including electromagnetic torque, stator current and voltage, efciency map are compared in detail by both the proposed method and experiments.