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Article – July 1, 2025 – By LarsonElectronics.com

What Is a Buck-Boost Transformer and When Should It Be Used?

What Is a Buck-Boost Transformer?

A buck-boost transformer is a type of single-phase or three-phase transformer used to slightly raise ("boost") or lower ("buck") voltage levels in an electrical circuit. It is most effective when voltage correction is required in the range of 5% to 20% of the system voltage.

Unlike a traditional isolation transformer, a buck-boost transformer is wired as an autotransformer, meaning the primary and secondary windings are electrically connected. This design increases efficiency and reduces size and cost.

When Should You Use a Buck-Boost Transformer?

Buck-boost transformers are typically used when incoming voltage is slightly above or below the required operating voltage of equipment. They are ideal for applications where the main voltage supply does not match the equipment’s rated voltage.

Common Use Cases Include:

Correcting voltage drop in long wire runs
Adapting 208V to 240V or vice versa
Balancing small voltage fluctuations in lighting or motor-driven equipment
Powering HVAC systems or commercial machinery with non-standard voltages

What Are the Advantages of Buck-Boost Transformers?

These transformers offer several benefits, especially for applications where only a small voltage adjustment is needed:

Advantage	Description
Compact Size	Takes up less space compared to full-size transformers.
Cost-Effective	Lower initial and installation cost.
Energy Efficient	Minimal energy loss during voltage adjustment.
Flexible Configuration	Can be wired in different ways to match various voltages.

Are Buck-Boost Transformers UL Listed?

Yes, many buck-boost transformers are UL listed when installed and used according to manufacturer specifications. Always verify compliance before installation in regulated environments.

How Do You Size a Buck-Boost Transformer?

Sizing depends on the input and output voltage, load kVA, and phase type (single or three-phase). It's important to use a manufacturer’s selection guide or consult an expert to choose the right model.

Need help selecting the correct transformer for your project? Click here to contact us for more information or to request a custom-built lighting and power solution. Larson Electronics – Building Trust Since 1973.

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What Is a Buck-Boost Transformer and When Should It Be Used? (7/1/2025)