It seems like you're asking about the concept of Fractional Detuning Factor in the context of A.C. (alternating current) Fundamentals. However, as of my last knowledge update in September 2021, I don't have specific information about a concept called "Fractional Detuning Factor" in A.C. Fundamentals. It's possible that this term might be specific to a certain context, course, or publication that has emerged after my last update.
If you could provide more context or details about what you're referring to, I'd be happy to try to help you understand or provide information to the best of my ability. Alternatively, if you have a different question related to A.C. Fundamentals or any other topic, feel free to ask!