Susceptibility of the winding switching technique for flux weakening to harmonics and the choice of a suitable drive topology

• Harmonic contamination in flux weakening using winding switching is investigated.
• It is found that 3rd order harmonics are introduced in this process.
• Contributions of 3rd order harmonics in this process are investigated.
• A suitable driver topology under harmonic conditions is also investigated.
• Sine wave, sine wave with 3rd harmonic and square wave drives are implemented.

The concept of winding switching for flux weakening of permanent magnet machines has recently evolved. Ideal sinusoidal flux and back-EMF of the machine are assumed for such a technique to demonstrate the flux weakening capability of the machine. In this paper, we present a real-world problem of a non-ideal sinusoidal back-EMF and investigate the susceptibility of this technique to the machine harmonics. Impacts of the harmonic contents on the field weakening capability of the machine under such conditions are explored. We show that the winding switching technique is particularly susceptible to 3rd order harmonics. Therefore, we investigate the impact of 3rd order harmonic components on the winding switching technique in details. Moreover, a suitable drive topology for the technique under harmonic conditions is investigated. Current control schemes for an ideal sine wave, a sine wave with fundamental and 3rd order harmonics, and square wave currents are discussed. All these drives are implemented, and the performance of the machine under these drives is compared. Simulation and experimental results are presented side by side to allow for analysis of issues mentioned above.