It’s a common situation. You’re in need of a transformer for a minor voltage adjustment. Say stepping up voltage from 208V to 230V. Nothing huge. You're considering a general purpose isolation transformer. But, the cost seems a little high when you only need a small conversion. So what’s the answer?

The buck-boost transformer. These units are an ideal solution when you only need a small voltage adjustment. 

Let’s look at what they are and their advantages and disadvantages.

What is a buck-boost transformer?

A buck-boost transformer is a small, compact transformer designed for +/- 5-20% voltage changes. These transformers are commonly used for applications such as HVAC units, lighting systems, or smaller industrial equipment. 

The name buck-boost comes from the transformer’s ability to slightly decrease (“buck”) or increase (“boost”) the voltage in a system.

Buck Boost Transformers in Different Systems

The number of buck boost transformers you need varies on your system type. 

In a single-phase system, you only need one buck-boost transformer to change the voltage.

In a three-phase system, you will need two buck-boosts if you have a Delta connection, and three buck-boosts if you have a Wye connection.

How is a Buck Boost Different from Other Transformer Types?

Here’s a quick look at the different types of low-voltage transformers.

Buck-Boost Advantages

Choosing a buck-boost transformer gives you several advantages. 

Cost Savings

Buck-boost transformers cost a fraction of a typical general purpose dry-type transformer. For example, when providing power for a 75kW load, your average three-phase transformer would normally cost around $3,300. A buck-boost transformer for the same application would only cost you around $900. 

Much like a commercial, zero-turn lawn mower for your quarter-acre yard would be overkill and cost more than what you need. The same comparison works between a buck boost transformer and a general purpose unit. Will it get the job done? Yeah, but you’ll be $15,000 poorer. And need another garage.

Efficiency

Buck-boost transformers are highly efficient at small voltage conversions since they only  perform a small voltage adjustment and don’t carry the full current load.  

Flexibility

Lastly, buck-boost transformers are small single-phase transformers, so they take up less space, are easier to install, and don’t require a complicated mounting system. If you are limited on space, buck boost is the way to go. 

Buck-Boost Disadvantages

Here are a few factors to consider when choosing a buck-boost transformer. 

Common HV/LV Neutral

If your load requires a neutral conductor, a buck-boost transformer may not work for your application. Since buck-boosts are essentially autotransformers, they won’t work if your load requires a neutral, and there isn’t a neutral in your panel upstream. Your service panel must provide the neutral for it to be used downstream. 

Limited Voltage Changes

Remember that a buck-boost transformer cannot perform a dramatic voltage change. A buck-boost cannot convert voltage beyond 20% of the original. If you need the unit to perform a conversion larger than that, you will need to use another transformer type. 

Stable Supply Voltage Required

The incoming voltage must be stable enough to remain within the +/- 5-20% conversion range. Because their maximum range of conversion is only 20%, buck-boosts are more sensitive to any voltage fluctuating near the top of the range. If the voltage varies too much, the buck-boost transformer could result in a load that’s either too high or too low.

150 kVA or Less

A buck-boost transformer can only handle loads with a kVA of 150 or less. The larger the degree of voltage adjustment, the smaller the maximum load that can be transformed.  If your transformer load is greater than 150 kVA, you will want to consider an autotransformer or a standard isolation transformer. 

Conclusion 

We hope this gives you a better sense of whether a buck-boost transformer is right for you. If you need a small, compact transformer for minimal voltage conversions, buck-boost transformers are an excellent option. 

Maddox has many buck-boost transformers in stock ready to ship to you. 

Fill out the form today to get the perfect transformer for your project.