From: Chuck Simmons
Organization: You jest.
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Subject: Re: Hard disk inductance, how to simulate/measure?
References: <email@example.com> <3DAE4804.99E0832E@webaccess.net> <firstname.lastname@example.org>
Date: Thu, 17 Oct 2002 06:14:40 GMT
NNTP-Posting-Date: Wed, 16 Oct 2002 23:14:40 PDT
The little lost angel wrote:
> On Thu, 17 Oct 2002 05:17:27 GMT, Chuck Simmons
> >If a fan motor is a brush type, you can directly measure the inductance
> >using an AC signal generator and a resistor to measure the inductive
> >reactance at some frequency. If the fan is a DC brushless type, it has
> Hmm, so the oscilloscope would be needed here?
> >electronics inside and you will be unable to measure anything directly
> >about the coils. Hard disk drive motors are technically AC synchronous
> >motors and coil inductance is easily measured. In another post I explain
> >how hard disk spindle motors are usually driven by the drive
> Thus to a power supply, the HDD would effectively be a resistive load?
Yes but the load is not constant. The head actuator uses a lot of
> Would it mean that in a normal system, if there is no DC brush fans,
> the PF would be 1.0 since there are no inductive loads, ie nothing
> else operates via the collapsing of magentic fields.
Power factor doesn't mean anything in DC circuits.
> Or would the load, whether 10% inductive or 100%, matters not since
> the PSU supplies x watts from an inductive mechanism anyway?
On the drive side of the PSU, the drive sees a reasonably stiff voltage
On the AC side of a PSU, the PF likely depends on the load on the DC
side but not on the inductance presented on the DC side.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com