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Old 31st October 2006, 05:21 PM   #1
percy is offline percy  United States
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Default Question about phase in an inductor

Below is an impedance chart of a ~1.9mh inductor. Blue is reactance, Yellow is phase. This was measured using Speaker Workshop (passive component measurement feature).

Click the image to open in full size.

Typically when I measure a capacitor or a resistor I get a dead straight line for phase (yellow) at 0° for a resistor and -90° for a capacitor. But when I measure an inductor the phase gets skewed like shown in the chart. It starts shifting towards 0 in the low frequency range. Why is that ? My guess is that it could be because of the DCR of the inductor.

I get similar results when I measure high value (1000uf+) capacitors. The phase starts shifting towards 0 in the high frequency range. Again, ESR ?



What do you guys think of an explanation for this ?
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Old 1st November 2006, 08:33 AM   #2
soongsc is offline soongsc  Taiwan
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How does your measurement.calib look?
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Old 1st November 2006, 10:58 AM   #3
sreten is offline sreten  United Kingdom
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Hi,

Think about it. What would a speaker inductor that could
maintain 90 degrees phase shift at 10 Hz look like ?
How low would its DCR need to be ? How big would the
core need to be for the current from your drive voltage ?

/sreten.
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Old 1st November 2006, 02:51 PM   #4
percy is offline percy  United States
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Quote:
Originally posted by soongsc
How does your measurement.calib look?
flat

Quote:
Originally posted by sreten
Hi,

Think about it. What would a speaker inductor that could
maintain 90 degrees phase shift at 10 Hz look like ?
How low would its DCR need to be ? How big would the
core need to be for the current from your drive voltage ?

/sreten.
so it IS about dcr/esr, right ?
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Old 2nd November 2006, 07:19 AM   #5
Tweeker is offline Tweeker  United States
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ESR in the main and interwinding capacitance?

Quote:
I get similar results when I measure high value (1000uf+) capacitors. The phase starts shifting towards 0 in the high frequency range. Again, ESR ?
This is in part an effect of the capacitors ESL. Special measures must be taken for a capacitor to be effective at high frequencies.
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