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Xtreme Cooling LN2, Dry Ice, Peltiers, etc... All the usual suspects |
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09-20-2003, 01:39 PM | #26 | |
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09-20-2003, 01:44 PM | #27 |
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where?
wj |
09-20-2003, 01:49 PM | #28 |
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OK. There PWM controller takes DC and chops it up. Giving a square wave output. That is not as destructive.
Most (inexpensive) dc motor controllers that have a 120/220 AC input and drive a 90/180VDC motor have a waveshape that is anything but a squarewave. The thing that destroys pelts from a bad power supply is thermal cycling, as I understand it. With a pure square wave all you are doing is turning the power on and off quickly. As you get away from a square wave the current starts to have more and more AC ripple. Which causes thermal cycling within the pelt. Someone like Since87 could do a much better job of explaining this than I. |
09-20-2003, 01:57 PM | #29 | |
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Edit: This link briefly discusses the deleterious effects of ripple from rectified AC sources. |
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09-20-2003, 02:03 PM | #30 |
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I understand what you have said and basically that is similar to what I've read.
My rant here is that on the surface the statement indicates that pwm is not the way to control a pelts power. I spent a lot of time trying to determine the correct way to control my pelts and found various pelt controllers, almost all of them use pwm. I'm not saying that pwm cannot hurt a pelt but just like aspirin, if you follow the directions and it was prescribed (designed) to do the job...it can without negative concequences. So is it fair to say that pwm CAN BE an effective way of controlling a pelt rather than saying it should be avoided as a means of control? wj |
09-20-2003, 02:11 PM | #31 |
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I'd say, 'Try to use a PWM controller that switches at 1 KHz or higher to be on the safe side.'
PWM shouldn't be dismissed all together, because it is by far the cheapest and most efficient method of controlling a TEC. |
09-20-2003, 02:11 PM | #32 |
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I just read the paper, thanks.
The conclusion was that the degradaton was insignificant, inconclusive and that the testing would need to be run up to 10,000hours for a more accurate determination to be made. I have been running a pelt chiller for around 14 months, 12~16 hours per day, 5~6 days a week. ( around 5,000 hours) Using a vpc controller, I am still using the same pelts and to date there have been no problems. wj |
09-20-2003, 02:18 PM | #33 | |
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By all means, yes.
All I was saying was that a PWM MOTOR controller (edit:w/AC input) is not designed for controlling power to a pelt. From TE's website: Quote:
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09-29-2003, 08:09 PM | #34 |
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Isnt there something called a line conditioner?
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09-29-2003, 08:23 PM | #35 |
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Heres an article I ran across. I'll apologize ahead of time if its a double post.
http://radiation1.mit.edu/Publications/j14.pdf Would adding a cap to the PWM signal smooth the signal enough?
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09-29-2003, 10:23 PM | #36 |
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What about using a car battery and having a charger on the battery all the time – The battery will act like a filter and the charger should keep the battery powered up.
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10-08-2003, 01:45 AM | #37 | |
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10-08-2003, 03:33 AM | #38 |
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Ill try and find a link, but one of the worlds biggest tec manafacturers (in china iirc) sell tecs that are able to withstand pwm control although the price is like 300% more than the same module that cant.
The problem with pwm cycling isnt the module itself its the ceramic incasing it. Ive got a tec with surface cracks all over the surface which i pwm controlled for a few months. Agreed the higher the frequency the better it should be but i would think you want to be hitting it with 100khz+ rather than 1000hz. ]JR[ |
10-08-2003, 09:10 AM | #39 | |
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Adding an appropriately spec'd inductor, in series with the parallel combination of TEC and cap, would effectively give you a crude switching DC regulator. This would be a good solution, but to the best of my knowledge, the inductor you would need is not something you can really buy 'off the shelf'. You could probably connect several inductors available from Digi-Key in parallel to get the desired performance. Edit: Also, the added inductor only becomes practical at high PWM switching rates. (100 kHz+) The inductor becomes too large at low frequencies. |
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10-24-2003, 03:32 AM | #40 |
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Anybody considered resonant power converter technology? I did my research on such for my BE. Coupled with a resonant power factor correction preregulator you can gain very good power densities.
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