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# Re: [femm] complex inductance???

- To: femm@yahoogroups.com
- Subject: Re: [femm] complex inductance???
- From: David Meeker <dmeeker@foster-miller.com>
- Date: Thu, 04 Oct 2001 11:11:32 -0400
- Organization: Foster-Miller, Inc.
- References: <20011003151004.7944.qmail@web10904.mail.yahoo.com> <3BBB68B3.5E021EF2@foster-miller.com> <001b01c14cdd$3c50dba0$4ca77a90@eee.metu.edu.tr>

Erdal Bizkevelci wrote: Hi everybody,I'm trying to calculate an inductance using the integral of A.J over the current passing coils. After calculating this, I will calculate the inductance from L=(core length)*(integral of A.J over the coil area)/(current)^2;But the integral gives a complex number (coil currents are real). So what is the meaning of a complex inductance value? Is it possible? Thanks in advance. Erdal`` The A.J integral is really just computing flux linkage. Eddy currents and hysteresis make the complex component, i.e. give the flux linking the coil in question a component that is not in phase with the current. The imaginary part of the resulting inductance is then associated with eddy current and hysteresis losses. Let me also put this another way. Say that you come up with some complex inductance, L, which could be decomposed as: L = Lr - j Li where Lr and Li are the real and imaginary components of L respectively. Now, consider the impedance that is implied: Z = j w L, where w represents the frequency in radians per second. Expanding this out, we get: Z= j w Lr + w Li So the imaginary part of the inducance contributes a real part to the impedance, associated with losses. You could interpret the (w Li) term as the frequency-dependent part of the circuit's resistance. The real part of the inductance the forms the imaginary part of the impedance, associated with inductive energy storage. You could also check out http://members.aol.com/dcm3c/pdf/chop2.pdf. This paper discusses how the eddy currents can give the inductance a complex component, and you can interpret it. Dave Meeker

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