Answer :
Final answer:
The statement is true; overcurrent protection devices like fuses and circuit breakers are rated to prevent excessive currents and ensure safety, and they may be rated at 125% of full-load current to handle transient conditions.
Explanation:
The statement that when a buck-boost transformer has a current of nine amperes or more, an overcurrent protection device is allowed to be rated at 125% of the full-load current is true. Overcurrent protection devices, like fuses and circuit breakers, are rated to ensure the safety of electrical systems by preventing excessive currents that could cause overheating and fires.
Electrical appliances and safety devices such as circuit breakers are rated in amperes, and rule of thumb is to use no more than 80% of a breaker's current capacity continuously. This precaution ensures that there is a margin for transient currents and for the protection of the wiring and connected devices. When dealing with transformers and their respective currents, an overcurrent protection device may indeed be sized larger to accommodate inrush currents or transient conditions, but it should ultimately safeguard the system within the limits specified by safety standards and engineering practices.
