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RecommendationImprovements in technology regarding the use of aluminum intransformers have made aluminum-wound transformers the ideal

choice for todays applications.

Rationale

Operating CostCooper Power Systems designs aluminum-woundtransformers with windings of a larger cross-sectional areathan would be used for a copper wound unit. This largercross-sectional area translates to a lower current density andan equivalent operating temperature. By reducing the currentdensity in the windings, a low-loss design can be achievedwith aluminum or copper windings.

ReliabilityA transformers life is defined by the life of its insulation system.

Because Cooper Power Systems aluminum-wound acopper-wound units run at equivalent operating tempthe insulation systems age at the same rate for each d

Lower First CostWhether low losses are the goal or not, aluminum wiare less expensive than copper windings. The followexample shows two equivalent loss designs, one witaluminum windings and one with copper windings.

The Bottom LineCooper Power Systems designs its aluminum-wound cousing the same thermal, dielectric and mechanical perforequirements as for its copper-wound coils. In pad-mousubstation designs, Cooper Power Systems aluminum-wunits and copper-wound units serve their loads equally w

Value Points - Copper vs. Aluminum Conduct

There is a common misconception that a distribution transformwith copper windings is in some way more efficient, morereliable, or has higher short-circuit strength when compared to transformer with aluminum windings.

For an in-depth, technical explanation on this issue, please see reference document R210-80-3.

B210-99028 April 2011 Replaces 99028

All Aluminum Winding All Copper WindingCopper Primary

Aluminum Secondary

No Load Losses (Watts) 2155 2272 2144

Load Losses (Watts) 17,725 17,225 17,544

Total Losses (Watts) 19,880 19,497 19,688

Efficiency at 50% Load 99.5% 99.5% 99.5%

Efficiency at 100% Load 99.2% 99.2% 99.2%

Dimensions (H x W x D) 72x 66

x 55

64

x 68

x 52

64

x 68

x 58

Price $36,745.00 $42,565.82 $39,843.27

Example: 2500 kVA, 3-phase padmount transformer, 13800 Delta - 480Y/277

In this example, while the losses of all three units are roughly equivalent, when compared to the price of thealuminum-wound unit, the copper-aluminum-wound transformer is $3100 (8.5%) more expensive, while thecopper wound transformer is $5800 (16%) more expensive.

Cooper Power Systems is a valuable trademark of Cooper Industries in the U.S. and other countries. You are not permitted to use the Cooper Trademarks without the prior written consent of C2011 Cooper Industries. A

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