Yaskawa General-Purpose Inverter Technical Information

Classification	Precautions on Application	Model	GN	Document No.	YEA-P-01-GN-01
Title	Power Line Harmonics Considerations for DC Drives and AC Drives

Page1 Page2 Page3 Page4 Page5 Page6 Page7 Page8 Page9 Page10 Page11 Page12 A 12-Pulse Transformer 12-Pulse Transformer (Harmonic Cancellation) Many Yaskawa Drives, including F7 have designed the flexibility of using two 6-pulse rectifiers in parallel to virtually eliminate power harmonics thorough phase manipulation. One 6-pulse rectifier just needs to be shifted by 30° in respect to the second 6-pulse rectifier. Phase manipulation is a result of converting power through a specifically designed transformer called a 12-pulse transformer. This transformer is different from auto transformers and phase shift transformers because the impedances on the secondary side are properly balanced. The transformer effectively eliminates the 5th and 7th harmonics in the core of the transformer. Since the 5th and 7th harmonics contribute to approximately 90% of the harmonic spectrum very high density packaging of drives to transformer size can be achieved. The result being a pure sine wave as depicted by the following waveform measured at the input terminals of the transformer. One Line Diagram and Input Current Waveform By utilizing the 12-pulse input transformer and a Yaskawa Drive, the end user can reduce current distortion levels by ~90%. The 12-pulse transformer configuration will meet the most strict power quality specifications such as IEEE519 -1992.