Estimating choke size ?

woody · 13th August 2003, 12:16 AM

I picked up a pair of chokes that I have almost no data on.
They are potted measure 2"x2.5"x3" measure about 1.5h
and 70 ohm. Would there be any way to estimate a safe current
rating given that data. There is a part # CUD 301149 and
901640-501 on them.

Thanks

Sch3mat1c · 13th August 2003, 04:12 AM

200mA would dissipate 2.8W (getting it maybe luke warm) and drop 14V. Sounds about right given the size.

To determine the magnetic maximum, you can connect it to an AC transformer (a good 600VAC) in series with a large resistor to limit current, and a smaller one (10 ohms) to measure it. Slowly bring up the voltage until you see clipping across the choke, then measure the current at the peaks (this requires an o-scope) just below clipping.
You can also test it for DC current by putting a rectifier between the HV winding and the current-limiting resistor; this will pretty much simulate in-circuit conditions.

Tim

av-trouvaille · 6th December 2006, 06:53 AM

Hello,

I have some chokes of 10H at 350 ohm in the drawer that I would like to test for maximum current. I do not understand quite what Tim is suggesting as a test.

I think it needs a variac to bring up the current to about 600 VAC or whatever voltage that is needed. Would a value of 100 ohm for the large resistor suffice? Doesn’t the choke need to be loaded by a resistor of a certain wattage to be able to pass current? How to determine the value of such a resistor?

How would one measure if the maximum of a DC-current is reached? Here no clipping can be seen I suppose. Is it by measuring the temperature when the choke heats up? This is risky as the internal wires will heat up higher and more quickly as the outside might suggest.

Could someone expand on the test method please?

Best, Arjen.

13th August 2003, 12:16 AM	#1
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Estimating choke size ? I picked up a pair of chokes that I have almost no data on. They are potted measure 2"x2.5"x3" measure about 1.5h and 70 ohm. Would there be any way to estimate a safe current rating given that data. There is a part # CUD 301149 and 901640-501 on them. Thanks

13th August 2003, 04:12 AM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	200mA would dissipate 2.8W (getting it maybe luke warm) and drop 14V. Sounds about right given the size. To determine the magnetic maximum, you can connect it to an AC transformer (a good 600VAC) in series with a large resistor to limit current, and a smaller one (10 ohms) to measure it. Slowly bring up the voltage until you see clipping across the choke, then measure the current at the peaks (this requires an o-scope) just below clipping. You can also test it for DC current by putting a rectifier between the HV winding and the current-limiting resistor; this will pretty much simulate in-circuit conditions. Tim __________________ Seven Transistor Labs Projects and Resources

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6th December 2006, 06:53 AM	#3
av-trouvaille diyAudio Member Join Date: Aug 2003 Location: Near Rotterdam	Hello, I have some chokes of 10H at 350 ohm in the drawer that I would like to test for maximum current. I do not understand quite what Tim is suggesting as a test. I think it needs a variac to bring up the current to about 600 VAC or whatever voltage that is needed. Would a value of 100 ohm for the large resistor suffice? Doesn’t the choke need to be loaded by a resistor of a certain wattage to be able to pass current? How to determine the value of such a resistor? How would one measure if the maximum of a DC-current is reached? Here no clipping can be seen I suppose. Is it by measuring the temperature when the choke heats up? This is risky as the internal wires will heat up higher and more quickly as the outside might suggest. Could someone expand on the test method please? Best, Arjen.