This paper deals with the generation of optimal current references for multiphase permanent-magnet (PM) synchronous machines in normal or fault mode (open-circuited phases). Current references are computed in order to keep a constant torque while minimizing instantaneous joule losses. In comparison with commonly used scalar methods, a vectorial approach makes it possible to reduce the number of computations in order to generate optimal current references in real time. In addition to this, since current references are expressed in terms of physical parameters of the machine, this approach can be used to evaluate the influence of machine parameters over the control performances. Finally, experimental results of a surface-mounted PM five-phase synchronous machine are provided in order to demonstrate the proposed strategy.