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Re: [Amps] FW: Power factor correction on tube amps

To: amps@contesting.com
Subject: Re: [Amps] FW: Power factor correction on tube amps
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 07 Mar 2013 16:59:40 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
On 3/7/2013 3:49 PM, KA4INM wrote:
No, the transformer is all inductive and the diodes conduct for most of the sine wave, but not all, at that transition the current changes abruptly causing distortion.

NO! Only the "imperfections" in a transformer are inductive (and capacitive, and resistive). The relatively inductance that we see in the circuit is "leakage inductance" -- and is due to the relatively small part of the flux from one winding that does not couple to the other. For any decent transformer, it's a very small fraction of the inductance of a winding.

The equivalent circuit of a transformer is complex -- in addition to the leakage inductance, there's resistance in the wire, resistance coupled from the core, capacitance between turns, capacitance between windings. At power frequencies though, we don't see the inductance or capacitance, only the resistance. And if we look into one winding, we see the load impedance on the other winding multiplied by the square of turns ratio.

73, Jim K9YC


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