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# Re: [femm] power factor

- To: femm@yahoogroups.com
- Subject: Re: [femm] power factor
- From: dcm3c@aol.com
- Date: Tue, 16 Oct 2001 12:16:18 EDT

In a message dated 10/15/01 7:50:41 PM Eastern Daylight Time, m_veinti2@hotmail.com writes:

> David,
> for a motor, do I have to enter currents as a complex number even
> though power factor is fix on materials and geometric features?
> Thank you
> Mercedes

This doesn't have anything to do with power factor. In a 3-phase induction machine, like you've been thinking about, you have to specify the currents at complex numbers to get the phases oriented correctly with respect to one another in time. The complex numbers map onto time using the formula:
i=i_real*Cos[omega*t] - i_imag*Sin[omega*t]
So if you had three-phase currents of amplitude i, the currents that you'd specify might be: i, i*(-1/2 + j*Sqrt[3]/2), i*(-1/2 - j*Sqrt[3]/2). These would be three currents of the same amplitude that are separated by 120 degrees of phase.
Dave.
--
David Meeker
http://members.aol.com/_ht_a/dcm3c

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