electro-Physics: 17.3409 volts

[Patrick Finnegan]

On Monday 13 December 2004 16:42, William Donzelli wrote:
> > Who would be using DC besides electro-platers?
>
> Old elevators. Lots of old elevators.

And, lots of not-so-old elevators.  There's a lot of elevators installed 
at purdue that use a 3ph AC->DC motor/generator set to run a DC motor 
for the elevator (which seems to typically be about 250VDC).  Doing 
that makes direction control simple (a DPDT relay can switch the 
polarity, and thus the direction), and (as someone else noted) gives 
good starting torque.

And speaking of old elevators, in one building, Purdue has an elevator 
still operating from the 1920s or 1930s.  Even controllers from the 70s 
(used in the dorm I lived in) still used piles and piles of relays to 
form the controller.  Some of the more recent elevators have (ick!) a 
Windows PC attached to them, presumably for programming type tasks, and 
a PLC of some sort to run the actual elevator.  I wouldn't trust 
anything as complex as a PC to directly control an elevator. 

Pat
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