Which safety device is best suited for protecting a transformer?

The best choice for protecting a transformer is a magnetic circuit breaker. Magnetic circuit breakers are designed to provide overcurrent protection by rapidly interrupting the circuit in response to excessive current flow, which can cause overheating and potential damage to the transformer. This type of breaker operates using an electromechanical mechanism that quickly opens the circuit when the current exceeds a predetermined limit.

Transformers can be particularly vulnerable to damage from short circuits or overload conditions, and the rapid response of a magnetic circuit breaker helps to minimize the risk of thermal degradation and failure. Unlike other devices, such as thermal fuses or hydraulic fuses, which may respond more slowly or rely on heat buildup to function, magnetic circuit breakers react instantaneously to fault conditions, making them a more effective means of protection for transformers.

In addition, while an electromagnetic relay can be used in certain applications for control and protection, it typically doesn't provide the same direct overcurrent interruption capabilities as a magnetic circuit breaker. Therefore, for the specific need of transformer protection, the magnetic circuit breaker stands out as the most appropriate device.