Control of Harmonics Using Delta-Wya and Delta-Delta Transformers, 1998 Process Control, Electrical & Info. Conference Proceedings

Power transformers with properly selected windings can be used to cancel most of the harmonics from large variable speed drives. This significantly reduces the need for harmonic filters and other high maintenance harmonic mitigation equipment, both in new projects and in situations where harmonics must be reduced. This makes it easier to use high power factor diode input drives which have harmonic content levels almost double the levels of low power factor SCR drives. However, harmonics must be reliably estimated to justify power system plans in the design phase of a project. Harmonics in the distribution system can be estimated using methods described in IEEE-519 [1,2], but individual drive data needed for the estimate is hard to find. Test results presented in this paper indicate the effectiveness of the use of delta-wye and delta-delta transformers. The individual drive harmonic data, the resulting system harmonic estimates, and test results are also presented for comparison.