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Registered Member #349
Joined: Sun Mar 26 2006, 10:50AM
Location:
Posts: 2
Hi,
some time ago I was experimenting with a MOT. As I was having a hard time trying to limit the current it pulls, I decided to go for a different approach, using a dimmer + cap to control & ballast the MOT. Similar to this one: The dimmer is home-made & is capable of handling 2760W. As for the caps: 8µF 250V "Heavy Duty" Engine start capacitor,three of them in parallel so 24µF total. Nothing mind blowing you would think but here's the deal:
When using any other ballast type or no ballast at all the arc ignites at 2 mm,what you would expect from a 2 kV supply but when i hook the MOT up to the dimmer + caps the arc ignites at almost 1 cm. So the MOT appears to produce a higher voltage. Second strange thing: the output voltage is higher when the input voltage is low but when I increase the voltage the MOT produces alot more current,that is until the MOT starts buzzing quite loud & no HV is produced. (Core saturation?)
What I can't figure out is why the MOT appears to produce a higher voltage when driven by a dimmer. I suspect it has something to do with the fact that it's running pulsed instead of CW but i can't find a decent explenation for this. Any suggestions?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
dimmer chopps halfwawes in order to reduce average power, and fast chopping obivously causes inductive kick in MOT (like it does with ignition coils, without dimer just on AC they would never generate high voltages).
And probably dimmer disallows MOT to operate at full power that way.
You could also rectify input and pulse the mot with strong igbts, what would be far more efficient than dimmer. Also increasing frequency to maybe few hundred Hz of pulsing you can push the MOT to much more power, using more input voltage untill you eventually blow the secondary because of overvoltage.
If it shows to be safe and secondary lives you could try to power a SGTC with single MOT that way.
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MOT + Dimmer = Increased voltage output
