A protein complex facilitating the electron transfer from an acyl-CoA molecule to ubiquinone via its flavin adenine dinucleotide (FAD) cofactor. Usually contains an alpha and a beta subunit and the structural cofactor adenosine monophosphate (AMP). Part of a system that oxidizes an acyl-CoA molecule and reduces ubiquinone and other acceptors in the electron transport system. [ https://www.worldcat.org/search?q=bn%3A0198506732 ]