50Hz vs 60Hz fixed drive speed ?

From: ghldbrd_at_ccp.com <(ghldbrd_at_ccp.com)>
Date: Tue Feb 17 15:13:32 2004

Hard drives are almost always driven by a DC motor (off the +12v line).
There is a speed servo thatt derrives its proper feedback from the servo
information formatted into the disk. Remember the only AC in a PC today
is the input bridge/caps that makes the DC voltage that the switch
transistor or FET turns into AC for the power transformer. That is how
they do autoranging, and they will work with just about any kind of input

The only problesm you have with 60 vs 50 Hz power is with synchronous
motors. This is a BIG problem with Hammond tonewheel organs shipped from
the US overseas to 50 Hz power.

Gary Hildebrand
St. Joseph, MO

> A friend and I were discussing 8" floppy drives recently, in particular
> that they often have two pulley sizes so that the rotational speed is
> 360rpm regardless of 50Hz or 60Hz operation, assuming that they are
> setup properly.
> The question then turned to whether or not a fixed hard drive would
> typically be designed in a similar fashion, such that the spindle
> would rotate at the same number of RPM when configured for 50Hz or
> 60Hz operation, or if they did not worry about the speed differences
> as the media was not removable?
> Of course todays modern hard drives are driven with DC motors, so
> they are not affected by the A/C frequency differences.
> Does anyone know what manufacturers routinely did on this account?
> --tnx
> --tom
Received on Tue Feb 17 2004 - 15:13:32 GMT

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