DRSSTC shielding and capacitor location
chris_inkubate, Sun Jan 31 2016, 10:53PMHello,
A little while back when having issues with my DRSSTC I put some shielding around my electronics in the form of plastic sheet with foil tape attached. I have since solved the problems by optimising other areas but left the shielding in place anyway. However when running 700-800A peak primary the below happened - looks like the shielding is picking up the primary field and heating up!
This is interesting as I have read discussion about the potential for this happening but never seen it and there is always some amount of metal under the coil in most cases. I'm a little concerned however as my tank capacitors are in much the same position as this shield was - and they are essentially foil and plastic too!
Has anyone else seen heating effects like this?
Chris
Re: DRSSTC shielding and capacitor location
Perezx, Mon Feb 01 2016, 05:31AM
Hm... You have HF EM field and a conductor in it... Why shouldnt it heat up?
Perezx, Mon Feb 01 2016, 05:31AM
Hm... You have HF EM field and a conductor in it... Why shouldnt it heat up?
Re: DRSSTC shielding and capacitor location
loneoceans, Mon Feb 01 2016, 09:09AM
This is expected behavior - the primary coil is essentially a big induction cooker, and also works pretty well as one. :)
loneoceans, Mon Feb 01 2016, 09:09AM
This is expected behavior - the primary coil is essentially a big induction cooker, and also works pretty well as one. :)
Re: DRSSTC shielding and capacitor location
Mads Barnkob, Mon Feb 01 2016, 09:27AM
I failed to find the pictures, but I think it was Dr. Spark that had shielding around the electronics underneath the primary that he burnt all the paint off when running high peak currents.
Try using net instead of flat planes. If I recall correctly you will have most current running along the edges and it will look like a 1 turn coil to the primary, much like the currents tends to run at the upper and lower part of a copper ribbon primary.
What was the distance to your primary, could you prove pictures with a better overview, than just the detail of damage.
Mads Barnkob, Mon Feb 01 2016, 09:27AM
I failed to find the pictures, but I think it was Dr. Spark that had shielding around the electronics underneath the primary that he burnt all the paint off when running high peak currents.
Try using net instead of flat planes. If I recall correctly you will have most current running along the edges and it will look like a 1 turn coil to the primary, much like the currents tends to run at the upper and lower part of a copper ribbon primary.
What was the distance to your primary, could you prove pictures with a better overview, than just the detail of damage.
Re: DRSSTC shielding and capacitor location
chris_inkubate, Mon Feb 01 2016, 01:10PM
Thanks for the replies. I've removed the shield anyway and runs ok. Primary is about 100mm above the shield. More worried now about the capacitors which are within the same distance. Think im going to raise the coil all up by 100mm or so more then use nesh as suggested for safety.
chris_inkubate, Mon Feb 01 2016, 01:10PM
Thanks for the replies. I've removed the shield anyway and runs ok. Primary is about 100mm above the shield. More worried now about the capacitors which are within the same distance. Think im going to raise the coil all up by 100mm or so more then use nesh as suggested for safety.
Re: DRSSTC shielding and capacitor location
Mads Barnkob, Mon Feb 01 2016, 02:56PM
A guess on why the foil would be burning is that is simply has much less mass and gets heated very easily compared to a thicker plate that would be able to dissipate more heat than it absorbs.
Mads Barnkob, Mon Feb 01 2016, 02:56PM
A guess on why the foil would be burning is that is simply has much less mass and gets heated very easily compared to a thicker plate that would be able to dissipate more heat than it absorbs.
Re: DRSSTC shielding and capacitor location
loneoceans, Mon Feb 01 2016, 05:30PM
Another good method is to make a shield with breaks located radially away from the middle to open up loops, but moving the primary coil up works great as well. Your caps are most likely fine - they have a much smaller flux linkage compared to your huge piece of foil and will probably be heating up much less than how they already be heating up from the tank current during operation.
loneoceans, Mon Feb 01 2016, 05:30PM
chris_inkubate wrote ...
Thanks for the replies. I've removed the shield anyway and runs ok. Primary is about 100mm above the shield. More worried now about the capacitors which are within the same distance. Think im going to raise the coil all up by 100mm or so more then use nesh as suggested for safety.
Thanks for the replies. I've removed the shield anyway and runs ok. Primary is about 100mm above the shield. More worried now about the capacitors which are within the same distance. Think im going to raise the coil all up by 100mm or so more then use nesh as suggested for safety.
Another good method is to make a shield with breaks located radially away from the middle to open up loops, but moving the primary coil up works great as well. Your caps are most likely fine - they have a much smaller flux linkage compared to your huge piece of foil and will probably be heating up much less than how they already be heating up from the tank current during operation.
Re: DRSSTC shielding and capacitor location
Perezx, Tue Feb 02 2016, 05:05AM
Perhaps you have noticed that without this shield your sparks are a bit longer :)
Perezx, Tue Feb 02 2016, 05:05AM
Perhaps you have noticed that without this shield your sparks are a bit longer :)
Re: DRSSTC shielding and capacitor location
chris_inkubate, Tue Feb 02 2016, 01:27PM
I saw a slight increase in output but not huge as was mentioned i doubt it was taking too much power. Just the thin aluminium was vulnerable. I may be able to tune it better now though and get more. Probably pushing my luck though as using mains ground with big arcs!
chris_inkubate, Tue Feb 02 2016, 01:27PM
I saw a slight increase in output but not huge as was mentioned i doubt it was taking too much power. Just the thin aluminium was vulnerable. I may be able to tune it better now though and get more. Probably pushing my luck though as using mains ground with big arcs!
Re: DRSSTC shielding and capacitor location
flyboy7777, Sun Feb 07 2016, 04:17AM
This makes me chuckle a bit... I was reading the user's guide to my induction stove today. One of the warnings was to never put any silverware on top of it. I guess the same applies to coils too!
flyboy7777, Sun Feb 07 2016, 04:17AM
This makes me chuckle a bit... I was reading the user's guide to my induction stove today. One of the warnings was to never put any silverware on top of it. I guess the same applies to coils too!
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