PEAK Transformers


A New Era in Transformer Design Standards that Optimizes Overload Capacity and Reliability in a Smaller Footprint.

Cooper Power Systems introduces PEAK™ transformer technology for reliable electric power voltage transformation with overload capacity to at least 112% in smaller, lighter units than comparable fluid-filled transformers.

Utilizing an advanced high-temperature insulation system approach — comprised of thermally upgraded kraft paper, Envirotemp™ FR3™ dielectric fluid, and an optimized core and coil design — a 75 °C Average Winding Rise (AWR) PEAK transformer results in a smaller footprint and a lighter unit capable of the same ratings as a physically larger 65 °C AWR rated unit.

Can the 75 °C AWR design be achieved using mineral oil-filled transformer technology?

No. Operating mineral oil transformers at elevated temperature will accelerate insulation breakdown. PEAK™ transformers exclusively use Envirotemp™ FR3™ dielectric fluid, a key technology that enables 65/75 °C and 75 °C AWR transformers to exceed ANSI required lifetime requirements and achieve the additional benefits of PEAK transformers.

What does AWR mean?

AWR stands for Average Winding Rise. This refers to the average above ambient temperature at the coil winding when the transformer is run at 100% load for a continuous period of time. Currently, most transformers operate at an AWR of 65 °C, however there are some 55 °C and 55/65 °C AWR transformers in service. PEAK transformers operate at ratings of 65/75 °C and 75 °C.

What is the difference between AWR and hot-spot temperature?

AWR refers to the average temperature rise that a coil experiences when operating at 100% load. Hot-spot temperature refers to the temperature at the hottest spot of the coil at 100% loading. Hot-spot temperature is normally assumed to be 15 °C above the AWR temperature. It is very difficult to measure the hot-spot rise.

What is a slash-rated transformer?

Slash-rated transformers are rated at two different temperature conditions, such as 55/65 °C, and have a corresponding kVA rating for each temperature. This allows for a transformer to be run at a higher loading and maintain its name-plated ratings.

How have slash rated transformers been used historically?

When thermally upgraded kraft paper was introduced to the transformer industry in the 1950s many customers used a slash rating of 55/65 °C AWR prior to transitioning to all 65 °C AWR designs. It was a way to slowly move toward 65 °C AWR.

Are PEAK transformers available with a slash-rating?

Yes, PEAK transformers are available in either single-rated or slash-rated designs. Slash-rated designs are 65/75 °C AWR.

Are there any additional steps necessary to order PEAK transformers?

PEAK transformer designs are integrated into our current quoting and design systems. It is now just as easy to get a quote for a PEAK transformer as it is a conventional transformer.

Are there any PEAK transformers currently being used by customers?

PEAK transformers have been created for some customers, by request, in order to meet their utilization needs. These customers are already experiencing the benefits of PEAK transformers in their specific applications and projects.

Is there an IEEE standard covering PEAK transformers?

Yes. IEEE Std C57.154™-2012 standard, covering the design, testing, and applications of transformers operating at elevated temperatures such as the PEAK transformer, is approved and was published October 30th, 2012.

Are Lead Times different for PEAK Transformers?

No.  Standard lead times for Cooper Power Systems transformers are published monthly and apply for PEAK Transformers just the same as mineral oil transformers.

Envirotemp™ and FR3™ are licensed trademarks of Cargill, Incorporated.