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Unread 06-18-2003, 10:05 AM   #18
jafb2000
Cooling Neophyte
 
Join Date: Jun 2003
Location: Cheshire, UK
Posts: 18
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DC Axial fans, especially PAPST, will not work in reverse polarity:
o They are reverse polarity protected
o DC fans work by a control circuit
---- fan start circuit
---- overheating/locked-rotor/stall detection & shutdown
---- fan speed maintenance since it is a DC not AC fan

Eg, if you stop some fans, they will stay stopped for about
1sec as the circuit has detected the stop, then auto-restart.
Larger industrial fans use thermal systems instead.

There is no way to reverse this operation, since the blades
are non-reversible and the voltage certainly is.

o Fan blades are also tailored to work in one direction
---- leading edge design
---- trailing edge design - usually feather-thin
---- shape & profile of the blades
-------- eg, Tunnel Vortex (Panaflo) vs Tangential airflow (PAPST)

Q: Why can't you simply reverse the fan?

--
Dorothy Bradbury
www.stores.ebay.co.uk/panaflofan (Ebay)
http://homepage.ntlworld.com/dorothy...ry/panaflo.htm (Direct Prices)
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