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Harmonic Mitigating Transformer

Product Overview & Application

Harmonic Mitigating Transformers (HMT's) are specially designed for non-linear loads which draw significant amounts of harmonic current. While K-factor rated transformers are simply designed to handle the additional losses of supplying non-linear loads, HMT's actually minimize the voltage distortion and power losses that result from harmonic load currents.

General purpose and K-Factor rated transformers have a high impedance to the flow of harmonic currents, and therefore, when harmonic currents are drawn by the load, significant voltage distortion can be measured on the transformer secondary. This voltage distortion leads to higher losses on nearly all devices supplied by these transformer, and depending on the amount of non-linear loading, can exceed the maximum 5% THD (IEEE 519).

Harmonic Mitigating Transformers provide a low impedance path to these harmonic currents by a combination of phase shifting and zero sequence flux cancelation:

  • Zero Sequence Flux Cancelation: The secondary windings of HMTs are specially designed such that zero sequence fluxes (3rd, 9th, 15th current harmonics) cancel out without being drawn from the primary and circulating in the primary delta winding. The flux cancelation provides a low impedance path for the zero sequence harmonic currents, which reduces the voltage distortion significantly. Furthermore, with no zero sequence circulating in the primary delta winding, the losses within the transformer are reduced significantly. 
  • Phase Shifting: The non triplean harmonics (5th, 7th, 11th, 13th, 17th & 19th) are mitigated by introducing of phase shifts on the secondary side of the HMT. Depending on the arrangement selected single, dual or triple output), specific harmonic currents can be mitigated without coupling them to the primary windings.

Product Specification

Capacity  15 to 1,000kVA Three Phase
Voltage Class  600V
Cooling  Self Cooled (ANN)
Frequency  60Hz (50/60Hz Optional)
Conductors  Copper (Cu) or Aluminum (Al) Windings
Insulation System  220°C (150°C rise) (optional 115°C or 80°C rise available)
Impregnation  Polyester Resin Dipped and Baked

 Meets North American Efficiency Standards:

  • U.S. - DOE 10 CFR Part 431 (Jan 1, 2017)
  • Canada - SOR/2016-311, Amd. 14 (Dec. 9, 2016) & ON Reg. 404/12Standard
Primary Taps  Typically +/-2 x 2.5% taps (refer to dry type distribution transformer catalogue)
Configuration  Single, Dual or Triple output 
Sound Level  Meets NEMA ST-20
Enclosure Type  Type 1 or 3R Indoor (refer to catalog)
Enclosure Finish  ANSI/ASA 61 Grey
Warranty  12 Months (See Warranty and Limitations)
Quality System  ISO 9001:2015 Quality Management System
  • CSA Certified - File # LR34493 (5kV Max, 900kVA Max)
  • UL Listed - File # E108255 (600V Max, 750kVA Max)
Reference Standards
  • CSA C22.2 No 47
  • CSA C9
  • IEEE C57.12.01
  • IEEE C57.12.91
  • IEEE C57.110
  • IEEE 519
  • NEMA ST-20
Optional Features & Accessories
  • Temperature Rise (115°C, 80°C)
  • Higher K factor load currents: K9, K13 or K20
  • Other Primary or Secondary Voltages
  • Different frequency (other than 60Hz)
  • Different NEMA Rated Enclosure (2, 3R, 4, 4X, 12)
  • Electrostatic Shield (single, double, triple or multiple/ultra)
  • Custom sizes (specific kVA ratings)
  • Open type (Core & Coils only)
  • Special Paint/Finish
  • NEMA TP-1 Energy Efficiency (USA); Part numbers will have /Z suffix