Can a motor consume more power at lower RPMs?

[dinofx]

I recently saw a power consumption chart for various hard drives. The 10K RPM drives consumed significantly less power than 7.2K RPM drives. Is there any explanation for this? The only thing I can think of is that they might have fewer platters, but once they are spinning I can't see how that matters.

 

[Styx]

The power of a motor is equal to the output speed (in Rad/s) multiplied by the torque (in Nm)

ie

P = Tw.

Higher speed for the same torque MUST use more power. The only explanation for this is the torque has come down. Two things

1) as you say less platters, this will reduce the mass as seen by the rotor

2) improvement in the rotor bearings. 7200rpm drives are EXTREAMLY cheap, they are cheap for a reason. Working at 7000rpm is alot easier then 10000rpm, thus they can get away with cheaper bearings, they cause extra drag/torque as seen by the rotor.

10,000rpm is pretty fast (yes you can get faster...) but it start creaping into the field of specialist bearings. A significant portion of the cost hike from 7200 to 10000 is purely in the bearings (they are extreamly smooth if you can get yr hands on one)