Richard Notton wrote:
> 3. All diodes, regardless of their voltage or current rating, have an
> inherent voltage drop of 0.7 (zero-point-seven) volts. Whatever voltage
> setting that is available at the input (anode) is reduced by 0.7 volts at the
> output leg (cathode) of these isolators.
Not so. The forward voltage drop is dependant on the type of semi-conductor the
diode is made of.
> We usually regard the forward diode voltage drop of 0.6V for ordinary silicon
> devices, germanium devices show a lot lower drop but are virtually extinct and
> do not come in high current form. Shottky and other modern constructions may
> show a lot more.
Shottky diodes have low forward voltage drops, typically 0.1 volt or less.
> It is important to note that the forward volt drop of a diode P-N junction is
> totally independent of current flowing
> through it.
Not so. A real diode typically has a fixed voltage drop plus a voltage drop
proportional to the current flowing through it.
>We are missing the point here, the charge current is dependant on the
voltage of the source supplying it.
Not quite. The charging current is determined by the difference between the
charging voltage minus the battery voltage divided by the circuit resistance.,
A voltage regulator has two functions:
It adjusts the field voltage up or down to maintain the correct charging current
independant of engine speed.
and
It monitors the battery voltage and restricts the output from the
generator/alternator so as not to overcharge the battery to prevent boiling or
electrolysis of the acid and the resulting mess.
Take care,
-John
This archive was generated by hypermail 2b29 : Fri Dec 07 2001 - 00:37:00 PST