I know that mains is 50Hz in Europe, but unfortunately a standard hub dynamo delivers roughly 34Hz at 20km/h, twice at 40 km/h, three times that frequency at 60 km/h ... and so on so forth. Furthermore I'm a bit afraid that using a "pure sine wave" as you're doing with your lab generator is a sort of a fancy approach not reflecting at all a real dynamo output that, as far as I can see, isn't a perfect sinusoidal shape at all. In conclusion ... I suspect that your tests are simply an overall nonsense, sorry for that.