Medium-voltage transformers
Completely self-protected single-phase overhead transformer
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Completely self-protected single-phase overhead transformer

Eaton’s Cooper Power series completely self-protected (CSP), single-phase overhead transformers deliver exceptional performance. With direct connected primary arresters, a MagneX interrupter or a secondary circuit breaker with internal primary voltage fuses, the CSP transformers eliminate the need for separately mounted protective devices while reducing installation costs. Available from 5–75 kVA (or 5–167 kVA with a MagneX interrupter), transformers can be filled with standard electrical grade mineral insulating oil or fire-resistant Envirotemp FR3 fluid.

5–167 kVA
Primary voltage
2400–19,920 V
Secondary voltage
120–600 V

Core features

  • Utilises internal overcurrent devices and arresters for overvoltage protection, without the need for separate external protection devices
  • Utilises a secondary breaker with weak link or an optional MagneX interrupter for secondary fault and overload protection
  • Meets or exceeds industry standards, including ANSI, NEMA and DOE energy efficiency standards
  • Constructed with EPRI-recommended interlaced core-type design
  • Cores and coils designed for high reliability and low field failure rates
  • Domed cover design and formed cover band provide increased pressure withstand capability, eliminate bushing overhang and improve cover retention
  • High-voltage bushing design improves gasket protection and seal

Internalised protection for installation cost savings

Transformers can be deployed with a variety of protection options, including a MagneX interrupter or a secondary breaker with weak link for secondary fault and overload protection; a primary weak link fuse; a current-limiting fuse for high interrupting ratings and limiting fault currents; a low-voltage, distribution class MOV arrester; and internal or external lightning arresters. These protection options eliminate the need to install external overcurrent devices and simplify power restoration.

Available with multiple fluid options

For fire-sensitive locations, Envirotemp FR3 fluid is recommended in transformers. The fire-resistant, natural ester-based fluid also offers the benefits of a soy oil-based dielectric coolant that is sustainable and has unique environmental and material properties. Transformers may also be filled with standard electrical grade mineral insulating oil.

Enhanced protection with optional MagneX interrupter

Eaton's Cooper Power series MagneX interrupter is an overcurrent protective device that protects distribution transformers from damaging overloads and secondary faults, and is also used for switching the transformer “on” or “off”. As a transformer protective device, the MagneX interrupter combines safety and efficiency with economic operation. It is designed for use in transformer (mineral) oil or Envirotemp FR3 fluid-filled transformers.