Insulation & Temperature

All Pioneer/Bemag transformers are designed and manufactured with the best quality insulation available. There are classes of insulation systems for different temperatures as defined by NEMA and ANSI. Insulation classes are rated in °C rise above a specific ambient of 40°C maximum. A transformer having a specific class of insulation, for example Class 220, can have an average winding temperature rise of 150°C with a maximum hot spot temperature rise of 180°C. If the room ambient temperature is 40°C, then the total temperature of the hottest spot would be 220°C. Pioneer transformers are designed to operate at rated load and voltage in maximum room ambient temperatures of 40°C, average room ambient temperature not to exceed 30°C, and at altitudes not to exceed 3300 feet in accordance with NEMA standards.

Insulating Classifications

The designations for insulation systems are numerical classifications based on temperature ratings. Transformer ratings are based on temperature rise. The accompanying table shows the designations.



80°C and 115°C Temperature Rise

Designed to supply a lower temperature rise (operating temperature) in order to give a safety factor on the transformer. This type of transformer is designed oversize.

General application and required where low heat dissipation from the transformer is needed.


  • Improve life expectancies
  • Cost saving on losses
  • Decreases watts dissipated
  • Substantial increase in overload capacity (20% at 115°C and 35% at 80°C rise)
  • High safety factor without increasing cable sizing and protection

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