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Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I've found what seems to be an inductive load while rummaging through smps's. This one is from a 200 W PSU, but I'm not entirely sure what its for, or if it is an inductive load at all. There seem to be three coils wrapped around the core, one primary and two coils which seem to be shorted. The primary seems to be one turn, or very few turns if any more.
If anyone has any knowledge on how it is actually built up, I'll be glad to hear. The core is a fair sized iron-laminate, so I think I can finally make that mains-xfrmr. I'm thinking of breaking the short on the larger coils and using them as primary and secondary. Any thoughts?
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
That is a power factor correction chocke. Computer PSUs are complex loads that only draw current when input voltage is higher than the voltage on the smoothing caps. This gives them a power factor lower than 1, and this inductor helps get the power factor closer to 1. You can read more about power factor here:
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
I'm surprised you found an iron core inductor in a smps, but if it is on the mains side and does its work at 60Hz, it makes sence. Sure you can use it to make a transfomer, try putting in in boiling water to get off all the goo, and then see how you can get the core apart.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
Boiling water had no effect, and it looks pretty hard to take apart. I want to save the wire too, which sure makes things a lot more difficult. Would it be possible to wind a primary on the outside of the inductor? How would the flux work then? Otherwise I'll have to cut the inductor somewhere in the middel, and end up with a 1:1 transformer.
Registered Member #51
Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263
Well I dont know exactly why, but just looking at the shape of the core I would say you cant wind anything on the outside. You would have to get your wire through the center gap between the 2(?) coils already there.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I've decided to just make a 1:1 xfrmr, just to make sure things are working like they should. I cut the wire that connects to two coils, and it is now roughly 1:1. So I set it up with a 40W light bulb as a load, and plugged it in. Next thing I know the circuit breaker has tripped. Am I missing some transformer fundamentals or does it just not like running at 1:1? It is a laminate core, so it should work at 50/60 Hz.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
The volts-per-turn of a transformer is proportional to the cross-sectional area of the core. For your transformer there are not enough turns for direct mains voltage and the core saturates - making the transformer look like a very low impedance - which trips the circuit breaker.
You need to operate at lower voltage or more turns (or higher frequency)
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I dont think there is a point to make a 50Hz transformer out of a choke. ž
You have to wind lots of fine turns for primary, and probably there is simply not enough space to put it in, and all for few watts in the end. Get yourself few small transformers and wire one backwards (if you need low-power isolation transformer) or if you'd like to wind something get one huge core, mot, dead NST etc. and have fun.
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Inductive Load
