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Old 30th July 2011, 05:33 AM   #1
bravi is offline bravi  New Zealand
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Default Swinging choke value in PSUD

I have a huge UTC ls 98 swinging choke that I wish to use in a choke input supply. The specification for this choke is 8 to 40Hy, 400ma current. What value should I use in PSUD?
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Old 30th July 2011, 06:20 AM   #2
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It will depend on the DC current through the choke. It's likely that 40Hy is at zero DC and 8Hy is at max rated DC current.
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Old 30th July 2011, 09:38 AM   #3
bravi is offline bravi  New Zealand
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Default Swinging choke- estimated current

Thanks for the reply.
The current demand on the power supply will be around 180 ma. Would mid point value in the 8 to 40 Hy range be a good approximation?
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Old 30th July 2011, 12:14 PM   #4
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Is there a datasheet for your choke to indicate what its max rated current is?

The fall off in inductance with current in a swinging choke is likely to be similar in character to that in a normal choke, but with the max rating point moved. Although the swinging choke may have a rapid initial drop in inductance, depending on how the magnetic circuit is configured.

Last edited by trobbins; 30th July 2011 at 12:16 PM.
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Old 30th July 2011, 01:23 PM   #5
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hey-Hey!!!,
IIRC that one was rated at 40 Hy at 40 mA and 8 Hy at 400 mA. Draw a line between those tow points and I think it will be close. Now the drop in L per mA probably isn't quite a straight line, but I'll bet you wind up with at least 12 Hy at your proposed loading.

I remember seeing those chokes at Surplus Sales of NE for ~$200 each and I very much regret not acquiring two of them. Most likely won't see any more either, I know for sure I wouldn't turn any I had loose...
cheers,
Douglas
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Old 30th July 2011, 03:29 PM   #6
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Actually, you can still find swing chokes on flea-bay.
I bought two NOS/NIB Thordarson swinging chokes (max. current 250ma & 300ma respectfully) for around $75/delivered.

Steve
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Old 30th July 2011, 08:41 PM   #7
bravi is offline bravi  New Zealand
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Thanks for all the replies.

The data sheet from UTC specifies DC current at 400ma. The DC resistance was specified as 90 ohms but actual measurement showed a value of 125 ohms.

I purchased this a few years ago on ebay for around 100USD and postage to NZ for this boat anchor was not horrendous. Its in near new condition.

I have used 20Hy as the value to simulate the intended supply in PSUD. Just wanted to check with the DIY community for any experience in this regard.

Last edited by bravi; 30th July 2011 at 08:43 PM.
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