Answer :
Final answer:
The statement is true; buck-boost transformers can be indeed wired with subtractive polarity to lower the source voltage. This allows the transformer to reduce the input voltage to meet specific equipment requirements.
Explanation:
The statement that buck-boost transformers can be wired with subtractive polarity to buck the source voltage is true. Buck-boost transformers are designed to adjust the level of voltage supply either upwards (boost) or downwards (buck) to meet specific requirements of the electrical equipment being used. When we say that a transformer is wired with subtractive polarity, it means the polarity marks (like dots or X1, H1) on the primary and secondary sides are opposite to each other, which results in a decrease in output voltage in relation to the input voltage when used in a buck-boost configuration.
For example, if you are using a buck-boost transformer and the input voltage is higher than needed for your device, you'd wire the transformer in a buck configuration with subtractive polarity to reduce the voltage to the appropriate level. Conversely, if you need to increase the voltage, you would use an additive polarity to wire it in a boost configuration.
The characteristics of a step-down transformer, which are pertinent here, include having a higher primary voltage than the secondary voltage, and typically a lower primary current than the secondary current, due to the principle of conservation of energy and the necessity to maintain power balance (Pp=IpVp=IsVs=Ps).
