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Dry-Type Transformers

High-Efficiency Dry-Type Transformers

Transformers reduce the voltage of the electricity supplied by your utility to a level suitable for use by the electric equipment in your facility. Since all of the electricity used by your company passes through a transformer, even a small efficiency improvement will result in significant electricity savings. High-efficiency transformers are now available that can reduce your facility's total electricity use by approximately 1 percent. That's good for your company; it's also good for the environment. Reduced electricity use provides cost savings for your company; it also reduces air emissions from electricity generation.

Two types of energy losses occur in transformers: load and no-load losses.

Load losses result from resistance in the copper or aluminum windings. Load losses (also called winding losses) vary with the square of the electrical current (or load) flowing through the windings. At low loads (e.g. under 30 percent loading), core losses account for the majority of losses, but as the load increases, winding losses quickly dominate and account for 50 to 90 percent of transformer losses at full load. Winding losses can be reduced through improved conductor design, including proper materials selection and increases in the amount of copper conductor employed.

No-load losses result from resistance in the transformer's laminated steel core. These losses (also called core losses) occur whenever a transformer is energized and remain essentially constant regardless of how much electric power is flowing through it. To reduce core losses, high-efficiency transformers are designed with a better grade of core steel and with thinner core laminations than standard-efficiency models. As well, new transformer core designs are emerging that use amorphous metal instead of the traditional silicon steel. These amorphous core transformers, available from major transformer manufacturers including GE, ABB and Howard Transformers, offer up to 80 percent lower core losses than conventional transformers.

Total transformer losses are a combination of the core and winding losses. Unfortunately, some efforts to reduce winding losses increase core losses and vice versa. For example, increasing the amount of conductor used reduces the winding losses, but it may necessitate using a larger core, which would increase core losses. Manufacturers are developing techniques that optimize these losses based on the expected loading.

Since January 2005, dry-type distribution transformers have been covered by Canada's Energy Efficiency Act and Energy Efficiency Regulations. These require that dry-type transformers sold in Canada meet minimum energy performance levels, as specified in CAN/CSA-C802.2-00, Minimum Efficiency Values for Dry-Type Transformers by the Canadian Standards Association.

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