Interactions between time and spatial harmonics in a series-connected five-phase two-motor drive

The multi-motor drive concept is based on the use of the additional degrees of freedom available in multiphase motors to independently control a group of series-connected machines fed from a single voltage source inverter. To achieve this independent control, the motors should have a perfectly sinusoidal distribution of the stator windings. However, due to non-linearities in the real motors, low order harmonics appear in the system. Depending on their origin, two main types of harmonics are present in multiphase machines, time and spatial harmonics. These harmonics produce additional losses and parasitic torques in the series-connected machines. This paper analyses the relationship between low-order spatial and time harmonics and its effects in a series-connected five-phase two-motor drive through experimental results collected from a laboratory setup.