Electrician's Licensing Practice Exam

When installing an autotransformer, is it required to insert an OCPD in series with the shunt winding?

1. Yes, it is always required

2. No, it is not required

3. Yes, but only for transformers over 100 kVA

4. No, but it is recommended

The correct answer is: No, it is not required

When installing an autotransformer, it is not required to insert an overcurrent protective device (OCPD) in series with the shunt winding because of the operational characteristics of autotransformers. An autotransformer's design allows it to share current between the primary and secondary windings; hence, the risk associated with fault conditions is managed through the transformer’s features and the placement of protective devices on the primary side, where the whole transformer system is fed. The overarching principle is that the existing protective measures for the transformer system are deemed sufficient to handle faults and overloads without the necessity for an additional OCPD specifically for the shunt winding. This design consideration aligns with industry standards and practices, emphasizing an efficient and safe electrical installation. In certain scenarios, while additional protection could enhance safety, it is not mandated, underscoring that the standard practices and regulations already provide a protective framework for the equipment within its rated capacity and intended usage.