Posted by: ConRAD
Re: Dynamo Voltage (possible) Hazard - 10/29/18 08:25 AM
Hi derSammy, thanks for your reply.
Yes I agree with you, at 50 km/h is definitely much better to keep both the hands on the handlebar !!
Here below nevertheless some of my points:
A bike dynamo is a constant current source till the load is a prevalent resistive load and its value is negligible compared to the internal reactance of the dynamo; 500-600 mA is the maximum output you can get from a dynamo, even at 100 km/h on a dead short-circuit load !!
Yes I confirm: no-load voltage is something like ~1V per km/h.
A 6V-3W hub dynamo is capable of delivering 6W at 20 km/h, 10 W at 50 km/h.
Output voltage of a dynamo of course is likely to drop with load but the typical 1500 Ohm of a human body will not affect substantially this value at all.
... sometimes just a few mA can kill and that's why worldwide households electrical protection, at least against "indirect contacts", has been generally specified to be put in place through the installation of a good grounding system in combination with a 30 mA RCD-Residual Current Device.
The IEC
plot below shows that 100 mA for 1 sec might be lethal.
Cheers
Yes I agree with you, at 50 km/h is definitely much better to keep both the hands on the handlebar !!
Here below nevertheless some of my points:
A bike dynamo is a constant current source till the load is a prevalent resistive load and its value is negligible compared to the internal reactance of the dynamo; 500-600 mA is the maximum output you can get from a dynamo, even at 100 km/h on a dead short-circuit load !!
Yes I confirm: no-load voltage is something like ~1V per km/h.
A 6V-3W hub dynamo is capable of delivering 6W at 20 km/h, 10 W at 50 km/h.
Output voltage of a dynamo of course is likely to drop with load but the typical 1500 Ohm of a human body will not affect substantially this value at all.
... sometimes just a few mA can kill and that's why worldwide households electrical protection, at least against "indirect contacts", has been generally specified to be put in place through the installation of a good grounding system in combination with a 30 mA RCD-Residual Current Device.
The IEC
plot below shows that 100 mA for 1 sec might be lethal.Cheers