measure inductance

henryp · 5th July 2006, 06:58 PM

IS THERE ANYWAY I CAN MEASURE INDUCTANCE IN THE PRIMARY
AND SECONDARY OF A POWER TRANSFORMER. I HAVE LIMITED EQUIPMENT - AUDIO OSC AND DIGITAL VOM.
I HAVE A NUMBER OF SMALL POWER TRANSFORMERS AND WOULD LIKE TO USE ONE AS A FILTER CHOKE - PRIMARY IN SERIES WITH
THE HIGH VOLTAGE SEC.
THANKS IN ADVANCE FOR ANY HELP.
PHH

Cal Weldon · 5th July 2006, 06:59 PM

Hi Henry,

Please post without your caps lock on.

Thank you

lndm · 5th July 2006, 11:44 PM

Hi henryp,

I assume you're aware of the limited current you'll be able to push through a power transformer, and the fact that inductance will alter along with core saturation.

Put a 10k resistor in series with the winding and connect the string across your oscillator (I am assuming the osc Zo is insignificant). Sweep until the V across the resistor is 0.7 times the oscillator's Voutput. At that frequency, the inductive reactance equals 10k.

Due to interwinding capacitance, it will be necessary to get a good reading below about a couple of kHz. If you sweep up and find the frequency of the minimum voltage across the resistor, make sure your reading was at a significantly lower frequency, otherwise use a different value of resistor.

5th July 2006, 06:58 PM	#1
henryp diyAudio Member Join Date: Aug 2003 Location: Fredericksburg.Virginia	measure inductance IS THERE ANYWAY I CAN MEASURE INDUCTANCE IN THE PRIMARY AND SECONDARY OF A POWER TRANSFORMER. I HAVE LIMITED EQUIPMENT - AUDIO OSC AND DIGITAL VOM. I HAVE A NUMBER OF SMALL POWER TRANSFORMERS AND WOULD LIKE TO USE ONE AS A FILTER CHOKE - PRIMARY IN SERIES WITH THE HIGH VOLTAGE SEC. THANKS IN ADVANCE FOR ANY HELP. PHH

5th July 2006, 06:59 PM	#2
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Hi Henry, Please post without your caps lock on. Thank you __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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5th July 2006, 11:44 PM	#3
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Hi henryp, I assume you're aware of the limited current you'll be able to push through a power transformer, and the fact that inductance will alter along with core saturation. Put a 10k resistor in series with the winding and connect the string across your oscillator (I am assuming the osc Zo is insignificant). Sweep until the V across the resistor is 0.7 times the oscillator's Voutput. At that frequency, the inductive reactance equals 10k. Due to interwinding capacitance, it will be necessary to get a good reading below about a couple of kHz. If you sweep up and find the frequency of the minimum voltage across the resistor, make sure your reading was at a significantly lower frequency, otherwise use a different value of resistor.

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