A method of controlling a multi-phase electrical machine by means of a power converter, wherein the method includes: a) controlling the electrical machine by utilizing vector space decomposition, VSD, wherein the controlling involves releasing control of the current of a harmonic while maintaining control of the current of the fundamental, b) measuring phase currents of the electrical machine while the control of the current of the harmonic is released, c) transforming the current measurements using VSD to obtain a current signature of the harmonic, and d) determining whether a fault is present in the electrical machine or the power converter based on a comparison of the current signature with a reference current signature of the harmonic.