The frequency spectrum produced by an inverter controlled by a delta modulator is examined. Analytical expressions are derived that model the spectrum. Computed spectra are compared to practical results, and good agreement is demonstrated. The analysis can be used to illustrate the dependence of the spectra on various modulator properties. The generation of sub- and partial harmonics within such a system can also be explained. A technique has been developed for eliminating sub- and partial harmonics by ensuring that the output waveforms exhibit quarter-wave symmetry. Practical results demonstrate that the technique is successful. The effects that imposing quarter-wave symmetry has on other aspects of the modulator's performance are also considered.