Modelling techniques are proposed for describing a two-phase axial-flux brushless motor in a direct-drive electric vehicle. Similarity transformation and singular value decomposition (ST-SVD) methods are used to linearize the system model. Stationary and cosecant coordinate models are derived on the basis of the methods proposed. Decoupled inductances and constant torque relations are also obtained. The model proposed is a very useful aid in describing the system dynamics. Simulation and experimental results are illustrated to verify the validity of the model. The given system modelling techniques can provide valuable mathematical models for associated vector control.