Abstract POLAR FIELD-ORIENTED CONTROL with 3RD HARMONIC INJECTION Martin Todd Hess Field Oriented Control (FOC), also known as vector control, is a widely used and well documented method for controlling Permanent-Magnet Synchronous Motors (PMSM) and induction motors. Almost invariably the orientation of the stator and rotor (field) fluxes are described in rectangular coordinates. In this thesis we explore the practicality of using polar coordinates. Third harmonic injection is also a well-known technique that allows full utilization of the bus (DC-link), thus allowing the motor to run to full base speed without the use of field weakening. This technique potentially allows a 15.4% improvement in the available bus. It has fallen out of use since it requires direct knowledge of the terminal voltage vector angle. The use of polar FOC permits the use of third-harmonic injection. We believe the combination of FOC and third-harmonic injection to be unique, and we present this paper as a novel contribution to the literature on the subject of motor control.