Final answer:
Transformers transform voltages via induction, with the number of primary and secondary turns determining if it's a step-up or step-down transformer. The actual number of primary bushings on a transformer depends on its specific design and function.
Step-by-step explanation:
Transformers are electrical devices that use induction to transform voltages from one value to another. The phrase 'transformers with this designation' likely refers to a particular type of transformer characterized by the number of primary bushings it has and the way it can be connected. A transformer can have a different number of primary and secondary turns; this is determined by whether it is a step-up transformer (more turns in the secondary than in the primary) or a step-down transformer (more turns in the primary than in the secondary).
In a typical transformer, as described in the given text, there are two coils, the primary and the secondary, wound around a ferromagnetic core. The primary receives the input voltage, and due to Faraday's law of induction, a time-varying magnetic flux induced by the alternating current (AC) in the primary coil generates a corresponding AC output voltage in the secondary coil.
Therefore, the number of primary bushings would be based on the specific design and function of the transformer. It is possible for the transformer to connect phase-to-phase or phase-to-ground depending upon its application and electrical network requirements.