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Registered Member #1517
Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304
I am using terry blake's propeller design, and I seem to be getting some bad spark behavior. It concerns me because the behavior is very irregular.
As I begin to spin up, the sparks seem tame, and occur every so often, with no definite pattern. After I reach maximum potential, the sparks seem to trail with the electrode. So the pulse lasts for a bit longer than expected, no real trouble, its just the spin up and down that concerns me for coil operation.
Will the irregular behavior have a potentially bad effect on my circuit? Will the transient behavior blow my capacitors up?
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
I get that on my rotary too, it happens.
As far as spin down is concerned, never power on when the motor is going slow enough to give you only a few breaks per second. It overstresses the transformer and can kill it. I was just goofing around with a real champion of a 12/60 and killed it one day doing just that. So... don't .. it's a bad idea.
Registered Member #1517
Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304
Ok, So I hooked the gap motor up to its own circuit. But the behavior is still irregular.
It seems like my entire system is very unstable. I'll get one or two good runs in, where it starts up immediately and produces good sparks, but then I will try and turn it on and it wont start up at all. I hear a buzzing noise, like the sound of a high voltage line, but no sparks.
I think this might mean that my connections in my circuits are somehow interfering with my operation. I am using regular crimp eye wire holders to terminate at connection points...
Another interesting effect is the sensitivity of the coil to changes in the environment around it, how much does a person usually affect the topload capacitance of a coil?
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
coillah wrote ...
Another interesting effect is the sensitivity of the coil to changes in the environment around it, how much does a person usually affect the topload capacitance of a coil?
Well, if a topload has as much capacitance as it does, even when so far away from ground, i am sure it would effect the capacitance quite a bit. When i made some of my own simple 555 sstc's if i got like within 6 inches to a feet from it, the sparks would disappear..
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
coillah wrote ...
no kidding... so I need to adjust the tap point each time I move the coil?
but will this help with the gap behavior? am I out of phase or something?
Well, tuning would not help with the gap, i don't believe. The way i think of it is tuning is just changing the primary inductance to resonate with the secondary. Well, no matter how much inductance you have, the voltage will be the same(well, not really, considering the resistance and any corona losses that may be present), but the current when it fires will decrease with more inductance. The current wont matter, because it does not effect the spark timing.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
What exactly is your cap/transformer setup?
I think you're getting bad results because your cap is undersized. From the picture I'm thinking its undersized because you do tend to see some amount of a streamer produced but for the most part you should have a pretty short and sharp discharge with a cracking sound.
Even when your primary is badly out of tune with your transformer/tank match you will hear a pretty well defined crack, but I'm thinking you're hearing more of a drone or loud buzzing with your gap. If that's the case I would go back and double check the caps, which ever type you're using, and double check your numbers.
And since you're dealing with a synchronous motor I would go back and double check to make sure if it doesn't need a capacitor to operate to its nameplate value. I've had a couple that needed a cap, so I would check that too.
I used to use a synchronous grinder motor, big 1/2 HP sucker that was a 1725 RPM unit. The trouble is that the nameplate speed is when its loaded down with a grinding wheel, so it was closer to synchronous speed with the rotary gap. I had some trouble with it because it would alias in and out of phase with the power, and give an amplitude modulated effect to my Tesla Coil. It was kinda funny, but mostly annoying.
Basically what I'm trying to say is you may be seeing a result of multiple problems all at once. So look at one thing at a time and triple check it, then narrow down the unknowns.
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Odd SRSG behavior
