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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [xj-s] electric fan -windmill
In message <5c390484.35b38fdb@aol.com> Juliansean@aol.com writes: > would the fan act as a generator? Or, would it create any > kind of electrical surge in the car's elecrical system? Yes and possibly. That is part of the reason why Jaguar and Bentley don't just switch the fan motors off, but actually short-circuit them when not in use. See below for the other beneficial effect of so doing. > To go further, > a) what happens when the fan is not powered but spinning fast and THEN it is > switched on by the thermostat control? Depends on how fast exactly it is spinning. Even so I suspect that the battery acts as a pretty large (read huuuuuge) capacitor, smoothing out any surge it may generate. Then again, because of the non-zero resistance of the path from the fan to the battery the surge will be bigger at the fan end. Short-circuiting the fan does not remove the generating characteristics, but makes the "generator" work very hard indeed. As a result, a short- circuited fan will freewheel much slower than one that isn't, so the above surge problem becomes a smaller one. Generally, though, car electrics are a very noisy environment and parts are normally designed to cope with that, spikes and all. > b) If the fan can't freewheel easily because it is acting like a generator > (windings are creating resistance to rotation) then wouldn't it act as an > impediment to freeflow of the air thru the radiator? Here's where I'm off my turf. Fluid dynamics isn't my strong side. Regards, -- Stefan Schulz jaguar@suaviter.demon.co.uk '88 XJ-S V12, UK version Follow-Ups:
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