Typical momentary power blip is perhaps 100msec. The thermistor won't change temperature much in that length of time- just look at it, and consider the relatively low operating temperature. Or check a data sheet.. the thermal time constant for the SL22 0R712 is 94 seconds!
Best regards, Spehro Pefhany
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You didn't happen to measure the current peaks before and after, did you? Probably not or you'd say so. That would be an interesting bit of info.
Best regards, Spehro Pefhany
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"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
They have poorer line-to-output AC isolation the conventional types with separated split windings. They usually have lower leakage inductance, which is bad for direct bridge-rectifier storage-capacitor setups as it leads to higher peak currents. Plus, they don't welcome adding a grounded primary-secondary inter-winding shield. But hey, what the hell, I like their low ac magnetic fields spreading into sensitive electronics.
In one of our products, we use a primary-side resistor-triac as both a surge limiter and a crude bang-bang regulator, to reduce the stress on downstream stuff as line voltage changes.
This was for an nmr gradient amp, in a rack with lots of stuff that doesn't like 60 Hz fields. We finally talked them into letting us use switchers - it took about 10 years - and they work great.
yeah, but it has to be 50% of Bsat, or the problem still occurs.
So Np doubles.
And given a full winding window, Rp quadruples.
I've since sold it, but I used to have a little 100kVA transformer I bought for $200, brand new. It ran at 250mT peak flux density. was designed for a motor test application, where it was switched on & off about once per minute, hence the tiny Bpeak. but the customer went broke and never picked it up, so it sat in the factory for several years, until I came along.
Joerg wrote in news:uryKh.8079$ snipped-for-privacy@newssvr12.news.prodigy.net:
While following this thread, I saw a couple of people mention R-cores. Would they not be better?
I'd once seen one and thought it was some eccentric variant on a toroid that someone made so they could mount it where their design once called for a chassis mounted E/I type, or had some other odd space restriction. I was so wrong. :)
From what I saw via Google once I'd seen the name 'R-core', I see that easy fitting of split bobbins directly round the straight long sections allows either a commercial firm OR a hobbyist to not only build their windings quickly and easily, but to modify them, as an assembled bobbin can rotate freely if wanted. Electrical isolation between windings can be better than in a toroidal type, which could be important for use in a medical device. The efficiency is good, and the flux well-contained, and they'd probably run as quietly as toroidals. Waste heat can escape from them more efficiently that either E/I types or toroidals. I'm surprised they aren't much more widespread than toroidals.
They used to be quite popular in TV sets. I believe I still have a few cores. Nowadays often just called U-U cores. For those who haven't seen them yet:
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One challenge with these is proper clamping. You can't inspect how snug the core halves are joining because it is inside the packets.
BTW your follow-up settings aren't right, was missing three NGs. That would have broken the thread for those folks.
The formers are made in 2 pieces that clip together and the winding machine spins the bobbins on the limbs of the core. The bobbins have 'gear teeth' to engage with the winding machine.
Joerg wrote in news:%jCKh.10629$ snipped-for-privacy@newssvr25.news.prodigy.net:
It does if you can w>>>I'm surprised they aren't much more widespread than toroidals.
What does 'bump up' mean? Re expense, if the bobbin can be rotated round the straight part of the former it's built onto, it would be a lot less awkward than winding a toroid, it would not be much more awkward that winding onto any spool. So why would it be more expensive than a toroid, given that the former is made the same way, and the windings are easier to wind?
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