A drive with a 12-pulse diode supply unit
Use a three-winding transformer, or two two-winding transformers:
• Connection groups: three-winding trasformer:Dy11d0 (or Dd0y1). Two two-winding
transformers: Dy11 and Yy0.
• Phase shift between secondaries: 30° electrical
• Voltage difference between secondaries: < 0.5%
• Short-circuit impedance of secondaries: > 5%
• Short-circuit impedance difference between secondaries: Impedance of transformer
windings must be equal, maximum <3% difference of the percentage impedance allowed.
(If short-circuit impedance Zk = 5%, variation can be maximum + 0.15%.)
• No grounding of the secondaries
• Static shield is recommended.
Two two-winding transformers
Three-winding transformer
Two parallel-connected supply units
See the appropriate supplement for the parallel-connected supply units, or contact ABB for
instructions in selecting the transformer(s).
Electrical planning guidelines 17
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