Locked Re: HT-37 transformer failure due to rapid STBY-->OFF-->STBY
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Well, something went wrong!? See missing section in bold. Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Friday, July 19, 2024 at 10:28:32 PM CDT, Jim Whartenby <old_radio@...> wrote:
Don Transformers are usually wound with the highest V/A winding closest to the core and then the next and so on.? Once the primary is wound, the B++ winding is next, then the tap is brought out and the B+ winding is done and the center tap is brought out.? Then the B+ tap and then the B++ winding which finishes the high voltage windings.?? Next is the two 5 volt heaters, most likely side by side.? So one 5 volt winding is connected to the B++ winding just below it.? The other 5 volt winding is connected to the B++ winding that is next to the primary winding.? That second 5 volt winding is also sitting on the top B++ winding but is connected to the bottom B++ winding. Taking your example of 880 RMS which has a peak value of 880 X 1.414 or 1.244 kV.? This is seen from the center tap to one of the B++ ends.? The 5 volt windings see twice this for a total difference of 2.488 kV. Make sense? Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Friday, July 19, 2024 at 08:26:16 PM CDT, don Root <drootofallevil@...> wrote:
Jim, re ¡° ¡. This would put perhaps more then a KV difference ?between one 5 volt winding and the second HV winding sitting just below it ? I wonder where you get the voltages from . ?we can see on the tube voltage chart 760 VDC on the filament ?but nothing about the plates and nothing about the transformer voltage that I can see. ??And I could not understand some reported voltages and I can¡¯t see some in the halli-manual ?but I finally found this: Presumably 880 is a no load voltage so it will run slightly lower depending on operating mode etc After much head scratching it seems that 880 VAC should boil down to something like 760 VDC for a choke loaded ?rectifier so now I ¡°see¡± 1760 rms volts across the HV terminals and that would be the prime stressor of that insulation, but under your construction idea, which must be close to the actual the 1760 will only take place between the 5V wdg and the nearby HV wdg , as you implied I think. So I am of the same thinking other than your? ¡° more then a KV¡± it could be at the end of a layer and the wdg to wdg insulation ?is not wide enough, and there is a creepage path ?around the end and perhaps corona.? Of course the 1760 could just breakdown? the insulation, as most people know the very ends have higher field intensity ?
? ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Wednesday, July 17, 2024 6:13 PM To: [email protected] Subject: Re: [HallicraftersRadios] HT-37 transformer failure due to rapid STBY-->OFF-->STBY ? Rick You are most likely correct, if the power transformer is still good after some 60 odd years, it may not fail, at least in that manner.?? ? Are the two 5 volt windings side by side on the same top layer?? If this is the case then I can see your corona effect between the high voltage winding closest to the core and it's associated 5 volt filament winding on the top most layer.? This would put perhaps more then a KV difference between one 5 volt winding and the second HV winding sitting just below it.? I didn't see this possibility till now; not having seen the actual transformer and how it is wound.? Is all of the insulation between layers paper or Mylar? Regards, Jim ?
-- don??? va3drl |
Jim Whartenby