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In today\u2019s short podcast, Bryan discusses buck-boost (auto) transformers and what they do.

Autotransformers are not automatic; the \u201cauto\u201d prefix comes from the fact that autotransformers only have one inductive winding. That winding is shared by the primary and the secondary, so it is not an isolation-type transformer. These transformers run current through the same winding used for induction.

Buck-boost transformers rise or decrease voltage. When the transformer \u201cbucks,\u201d it decreases voltage from primary to secondary, and a \u201cboost\u201d increases the voltage from primary to secondary. In other words, a \u201cboost\u201d is a step up, and a \u201cbuck\u201d is a step down on a small scale.

You can only wire these transformers if you use the manufacturer literature. There are many types of autotransformers, and you need to know the exact setup for your transformer\u2019s specific design. Generic diagrams will usually not suffice.

When sizing a buck-boost transformer, you must keep your start load in mind as well. As technicians, we might not be able to handle the specifics of sizing based on the start load, but it\u2019s still something to keep in mind.

The \u201cbuck\u201d configuration of the buck-boost transformer is especially helpful in markets where the utility company tends to produce overvoltage. Our specific setup uses the Micron J750A1EB1A02, which you can learn more about on YouTube HERE. The \u201cboost\u201d configuration helps when a motor doesn\u2019t get enough voltage from the utility source.

Before you buck or boost the voltage, remember to account for both sides of the equation; if the utility changes the voltage, you still want to be within range.

Bryan also covers:

• Ratings
• Current and capacity changes based on voltage
• Inverter-driven technology
• Voltage monitors (ICM493)

You can learn more about the 2022 HVACR Training Symposium HERE.

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