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Registered Member #1596
Joined: Fri Jul 18 2008, 08:43PM
Location: USA
Posts: 65
As soon as I solve one problem with excessive heat, another one arises. Its like there is a need for place to dissipate the heat! So, capacitors are fine now, but the inductor in series with primary overheats, and its made of 3 smaller diameter wires to account for skin effect and well overrated. If I remove the inductor, transformer will take the heat!!! My guess is because the idle voltage is around 10kV and once the arc ignites it drops to 1-2 kV, excessive voltage need to drop across something else and all that power gets dissipated. Is it right? Also, I noticed that as I get to 75-100% duty cycle, the idle voltage drops to around 7kV at 100%, why would that happen??? Please help!!! I really need an advice from an experienced professional like you guys. Oh an UF4007 also heat up considerably, though they survive with the forsed air cooling.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
baleworker wrote ...
My guess is because the idle voltage is around 10kV and once the arc ignites it drops to 1-2 kV, excessive voltage need to drop across something else and all that power gets dissipated. Is it right?
No, ideal inductor does not dissipate any power. It does "drop" power but only apparent one. The heat generated is because of current flowing through ohmic resistance of the inductor, so winding with thicker wire should help.
baleworker wrote ...
Also, I noticed that as I get to 75-100% duty cycle, the idle voltage drops to around 7kV at 100%, why would that happen???
I don't know, maybe at 50% you're exciting some parasitic resonance in the transformer which goes away at higher duty cycles. I have noticed this when playing with LOPT's.
Maybe you should define what "hot" means? Most semiconductors and magnet wire are designed for 150°C, so unless they are running over 100C you shouldn't worry. However watch the temperature of ferrite cores, they should NEVER get over 100C if you don't know the material.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
baleworker wrote ...
here is a waveform of what I call 100% duty cycle for SLR: Sry if I confused you guys
Thats what I call 50% duty cycle, or close to that. However it seems youre slightly below 50%, try increasing the duty a bit to something like 60%, here more is better than less.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Are you sure? I'd have thought that running a SLR at 50% or above would be asking for trouble with DC offsets and the like. It seems to me that you ought to let the second half-cycle end by itself, to make sure the current is zero and the inductor and transformer are reset, before you go turning anything on again.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Well when the current conducts through the clamp diode, it really does not care if the device is on or not. I have ran a SLR converter at 100% duty and the primary waveform was the same.
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SLR overheats, feel frustrated, please help!!!
