The overload protection mechanism of an x-ray generator should not permit an exposure that exceeds what percentage of the tube capacity for a single exposure?

The overload protection mechanism of an x-ray generator is designed to ensure the safety and longevity of the x-ray tube by preventing it from being exposed to excessive heat and stress. A fundamental principle of this protection is that the maximum exposure per single operation should not exceed a certain percentage of the tube's kW capacity to prevent damage.

Setting this threshold at 80% of the tube capacity for a single exposure ensures that there is a safety margin, allowing for the necessary cooling periods and preventing overheating that could lead to tube failure or other operational issues. This protective measure is critical in maintaining the x-ray tube's operational integrity and prolonging its useful life.

The other percentages would pose a greater risk of exceeding safe operational limits, risking thermal overload and potential damage to the x-ray tube, making them less suitable choices in terms of safety protocols established in radiographic practice.