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Re: Heating in 4-1/2 turn inductorFrom: Jeff_Johnson@Hotmail.com (Jeff Johnson) "amdx" <amdx@knology.net> wrote in message news:ec0b$4c7650d8$18ec6dd7$9856@KNOLOGY.NET...
What you describing is, L1 V L2 V1--/\/\--+--/--0 on the same core? L2, the 1/2 turn part of the coil is behaving wildly different than expect? After all, ideally L2 has resistance in direct proportion to the total winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the coil. In a Singles Chat">single coil the power dissipation of the 1/2 turn would also be ~ 11% and this is quite easy to see. You are saying that it is much more than this as if the ratio's were turned up side down. Something like the 1/2 part dissipating 90% and the 4 turns part dissipating 10%? if you agree with the layout of L1 V L2 V1--/\/\--+--/--0 Then it is easy to see that in ideal circumstances the current through L1 should equal that of L2 and the I^2R heating would produce the results I described first. Instead of assuming the two inductors are on the same core we can assume they are on different cores. This will help us understand if differences in flux could cause such problems. You mentioned in another post that you were using AC to drive the coil? Did the effect happen with DC? Did you measure the voltage on the 1/2 turn? Was the core itself generating the heat or was it due to the 1/2 turn? What was the total current through the coil? Was it possible the coil could have been shorting out on another turn or the core? Was it really 1/2 a turn getting hot or "just the end of it"? Was the coil tested by itself outside the circuit? If so did it exhibit the same phenomena? What was the end of the coil that generated the heat connected to? Was the connection itself possible cause for the heat? Was the coil reversed in the circuit? If so did it exhibit the same problem with the ends switched? You mentioned that you tried 4 turns and 5 turns and the problem went away. Did it go away completely or partially? Was those two coils made exactly the same way and connected the same or were they in any way different besides just the turn difference? Was the coil one continuous piece? the 1/2 turn was not spliced on? Did you try a 5.5 and/or 6 turn coil? Did the 1/2 turn end get hot very quick or did it take a while? Basically seconds or minutes? Did you try to change the direction of the core relative to the coil? If so did it make any difference? Is there any possible way the core itself could have been generating the heat at the 1/2 turn and the effect you experienced was just the core heating up that 1/2 first? Did you allow the inductor to run a long time? If so, What was the effect still? Was the whole coil hot or still just the 1/2 turn? Hopefully you can answer some of these questions. It sounds to me like you didn't do much troubleshooting so I expect most of them can't be answered so the true reason probably will not be known.
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