Let's break down how a buck-boost transformer works and then apply that to your scenario.

Understanding Buck-Boost Transformers

Buck-boost transformers are single-phase transformers designed to be wired in various configurations to either increase (boost) or decrease (buck) a voltage slightly. They work by using the additive or subtractive properties of series-connected windings. Primary (H windings)

The input voltage is applied to the primary windings (often labeled H1 and H2).

Secondary (X windings)

The secondary windings (often labeled X1 and X2) are connected in series with the primary.

Boosting

To boost the voltage, the secondary voltage is added in phase with the primary voltage.

Bucking

To buck (lower) the voltage, the secondary voltage is added out of phase with the primary voltage.

Calculations with Your Specific Transformer1. Transformer Voltage Ratios

Your transformer is rated for:

Primary

240V/120V

Secondary

24V/12V This means you can configure it to have either:

Primary

240V or 120V input

Secondary

24V or 12V output2.

Applied Voltage and Expected Boost/Buck

You are applying 208V to one of the primary voltage options. We don't know how it was wired. Let's analyze both possible scenarios to understand what the voltage coming from the secondary (X windings) will be.If it's wired for 240V input:

The turns ratio from primary to secondary would be: 240V/24V = 10 or 240/12=20 Since you're applying 208V instead of 240V, the secondary voltage would be approximately: 208V / 10 = 20.8V (from the 24V secondary) or 208V / 20 = 10.4V (from the 12V secondary)If it's wired for 120V input

The turns ratio from primary to secondary would be: 120V/24V = 5 or 120/12=10Since you're applying 208V instead of 120V, the secondary voltage would be approximately: 208V / 5 =

41.6V (from the 24V secondary) or 208V / 10 = 20.8V (from the 12V secondary)Important Considerations and Cautions



Wiring Configuration is Key

The actual boost or buck voltage depends entirely on how the primary and secondary windings are connected in series. There are specific diagrams for these connections, and you must follow them precisely.

Overvoltage Risk

Applying 208V to a transformer wired for 120V can cause over-excitation of the core. This will lead to excessive current draw, overheating, and potential damage to the transformer. Do not do this for more than a very short test!



Don't Exceed Nameplate Ratings

Never exceed the voltage or current ratings printed on the transformer's nameplate. This is crucial for safety and preventing damage.

Consult an Electrician

Working with electrical transformers and power distribution can be dangerous. If you're not a qualified electrician, consult one for assistance. This is especially true if you are unsure about the wiring configuration.

In summary:To determine the exact boost or buck voltage, you must know the intended wiring configuration (what voltage tap the primary winding is wired to) and understand how the secondary winding will be connected in series to either boost or buck. Flag for review