View Full Version : For you electrical folks!! Fan voltage booster...

06-01-2009, 11:58 PM
Here is my idea of a circuit to take 3 phase AC current directly from the
altarnator's stator winding, and use it through a transformer to boost the
voltage to the cooling fan motor.

This would add more power to the fan than a 12V system alone could provide.

The hard part would be finding an appropriately sized transformer core, and
determining how many turns of winding would work at the frequency range from
the alternator.



06-02-2009, 01:50 AM
In theory it would work, the only thing is you have to take into consideration that the frequency of the power coming from the alternator is entirely engine RPM dependant. Cause when the engine RPM changes so does the alt, the freq will be constantly varying in accordance with engine RPM....

still sounds neat though if you could get it to work

06-02-2009, 01:51 AM
They already make them for fuel pumps to boost the voltage for more flow. Most 3800 guys use either a Flowcharger or boost-a-pump. It would probably work fine with an electric fan as well.

06-02-2009, 01:53 AM
I am hoping (if I build this) that the increased frequency would only give the fan more voltage at higher engine RPMs.

If the new fan is adequate at normal system voltage I may not fool with it.


06-02-2009, 01:56 AM
That only works to an extent it all depends on what you use for a transformer core because different cores operate most efficently at different frequencies, one core may work great at idle and drop off above idle another core may work in the middle of the RPM range and drop off at high or low rpms etc, etc. Most transformer materials are designed to work in a very tight and specific frequency range soft iron 50-60 hz powdered iron 15-20k ferrite 25-250k depending on material make up and design.

Remember Transformers are more than meets the eye

06-02-2009, 02:00 AM
There will be a "sweet spot" for sure. One way and you get core saturation at low RPM's, too far the other way and inductive reactance will reduce the current to nothing. The conditions where this would be needed most are idle and off-idle. If the transformer was "tuned" to respond best at the frequency generated at idle, with inductive reactance causing it to taper off at high RPM's, that might be a good thing.

06-02-2009, 02:02 AM
Let me know if you can get it to work :)

06-02-2009, 02:08 AM
Will do.

I also thought of a capacitive voltage doubler. Trouble with that is it's most efficient at high freqiencies, when the fan is least needed. Plus there is no isolation so its output would have to pull the load by its self without being series with the battery like the transformer-based system.

I know they use laminated iron core transformers in 400 HZ aircraft power systems, so I bet I can get a laminated core transformer to work at alternator frequency; with the correct amount of turns on it.