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DC motors

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Posted by mark Ransley on October 10, 2003, 1:25 pm
DC  motors are  50 to 60% more efficient  and are used in some furnaces
and on the fan of the Artica refrigerator. So why arnt more products
using them. Table and ceiling fans etc. There are brushless DC s made,
is it reliability or cost. I think i would pay extra for a DC  fan.

Posted by Nick Pine on October 10, 2003, 2:53 pm

Grainger sells AC motors that are 96% efficient.
Would a DC version be 146-156% efficient? :-)


Posted by mark Ransley on October 10, 2003, 3:19 pm
 Nick then why do dc motor furnaces take 1/3 to 50 less power to run.
Because if i understand it they are more efficient.  As a DC furnace
increases AC seer by 1. You compared ac to ac, not dc.  My  AC  motor
furnace pulls  3a my new DC will pull 1a

Posted by Ian Stirling on October 10, 2003, 4:22 pm
You'r wrong.
AC motors (nearly all of them) beat 90% efficiancy.
DC motors are generally around the same, certainly not 30-50% better.

Apples and oranges.
The motor converts electricity to movement.
If you change the amount of mechanical force you need by changing the
appliance, then naturally the voltage will change.
Some AC motors may be very inefficient, but it's not inherent, and
is a design choice to use the inefficient ones.

http://inquisitor.i.am/     |  mailto:inquisitor@i.am |             Ian Stirling.
My inner child can beat up your inner child.                   - Alex Greenbank

Posted by mark Ransley on October 10, 2003, 4:49 pm
 Then how is Carrier  which uses the GE DC ecm  motor on  the Infinity
58mvp  getting its claim of  66% less electrical usage. I guess I am
missing it.  

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