Toroidal motor is a new type of motor. The basic structure of the motor is introduced. Spiral space current in the worm windings is analyzed. The magnetic motive potentials and magnetic linkages produced by two current components are developed. The inductance equations for the toroidal worm windings are deduced. Using these equations, the changes of the winding inductance along with the planet position angle for the drive system are investigated, and the oscillation and the period are discussed. The test of inductance measurement for the motor is done. Test results confirm the validity of the deduced equations. The results offer reference for the dynamic performance analysis and practical application of the novel motor.