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Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
I was trying to figure out what size core i need to make a ZVS driver. I know if it's too small, i risk overheating. So I wanted to make sure I get the right core.
I was going to get a few things at electronic goldmine, and figured I might as well get a core there (if any are good) but I believe they're too small. Need a torroid core. Where do you guys often buy yours at?
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
People usually use the yellow/white cores from ATX power supplies because the cores can be run with a DC current though the windings. Other people have used ferrite for cores but I don't know exactly how well that works out.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
The ZVS driver inductor needs to store energy. Therefore, by definition, there must be an air gap in the inductor's core so that it can store energy. This means that you CANNOT use pure ferrite cores without an air gap.
For low losses, especially in a ZVS driver, I recommend that you use a gapped E core, since the ferrite material provides lower core losses at higher frequencies. However, since these are relatively hard to find, you can also make the inductor using an iron powder core. I recommend the red #2 material instead of the yellow-and-white #26 material, because it has much better DC saturation and high frequency characteristics. The lower permeability of the #2 material means you will have to use more turns for a given inductance, but this is usually easily compensated for by using larger or paralleled wires.
You can easily order these kinds of cores from Amidon.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
You definately can use ferrite cores. I dont know why but I think their huge inductance makes them run at the "verge" of saturation while the current ripple is not that high because of the large inductance. For my first driver I used an ungapped core and adding a gap didn't make any difference.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
A zvs inverter needs TWO cores,
A) one for the resonant transformer B) one for the dc link inductor
Which cores you use depends upon the intended frequency (core material) and power level (core size)
For initial experiments I reccommend that for the dc link inductor you use an air-core inductor that will not saturate, e.g. a roll/reel of copper wire (mains wire, speaker wire, interconnect wire .... anything like that) This will allow you to 'test' your resonant transformer core without also testing the dc link core, one problem at a time.
Once your zvs is working well then experiment with the dc link inductor.
Material #2 is an old favourite of radio hams (I prefer #6, #7) Unless you're going to operate well above 100 kHz these materials are not required.
Iron powder cores are good but ferrite with an airgap is better (I think) If you can't find gapped ferrite try a ferrite aerial rod (for the dc link inductor too)
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
Sulaiman wrote ...
Iron powder cores are good but ferrite with an airgap is better (I think) If you can't find gapped ferrite try a ferrite aerial rod (for the dc link inductor too)
Ferrite cores with discrete airgaps are better than iron powder cores at higher frequencies because of ferrite's inherently lower core loss. If using the core at low frequencies or with DC, iron powder cores will yield better core utilization and smaller size.
If you use aerial rods (or any significantly open magnetic circuit type) be sure not to let the flux couple between the two magnetic parts (such as using ferrite rods for both the transformer and the inductor and placing them end to end). Also, the inductance for the rod configuration is somewhat unpredictable, but to get the best quality (Q and high inductance) the winding should be centered on the rod and spread out over the whole surface of the rod.
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Best place for ZVS Torroid cores?
