EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: anishkgt on March 19, 2017, 12:17:32 pm
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A few questions about the insulation part of a transformer that I plan to re-wind the primary. Is kypton or Mylar tape that I should go for or both one over the other ? What would be thickness for the tape to be used and how many turns of it.
Thanks in advance.
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I'd go for kapton tape. Thickness would depend on the transformer voltage and dielectric voltage of the tape. If you bought it from a reputable source it should come with a datasheet that tells you this.
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Oh thanks for the reply. So just kypton only ?
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Oh thanks for the reply. So just kypton only ?
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I can't really see any benefit of using two types of type. Maybe it would improve the dielectric strength but you could just increase the number of layers of kapton if needed.
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Cools sounds good enough. Then kypton it is.
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A few questions about the insulation part of a transformer that I plan to re-wind the primary. Is kypton or Mylar tape that I should go for or both one over the other ? What would be thickness for the tape to be used and how many turns of it.
What transformer is that? If typical 230vac household power transformer having a core size of 3cm X 4cm and using EI core of typical silicon steel 0.5mm thick, then the turns would be around 780 turns. Such low voltage, typical masking tape would be enough. The important is the primary and the secondary must be separated by the tape and no part of the coils between them should be touching each other [as good practice].
Actually understanding the principle is important. For example, if you wound the primary and secondary coils starting the turns together, 1 turn, 2 turns.... etc... the potential between the 2 coils are always the same, hence no tape is required. However if you wound all the primary first, as the turns increase the voltage potential also increases with the turns says 1000v at the top layer of the finished primary coil then you suddenly introduce/begin another turns starting at 0 v, then you will need to consider the potential difference and apply the appropriate tape. In High output transformer, there are the special bobbin with segregation slots specially designed for this. Typically if you have a centre tapped transformer example 0-120-230v, then typically the 2 halves would be start wound together. I can't explain very good but I hope you get the picture.
For your case, since you are rewinding the transformer, count the numbers of turns you unwound the old primary windings, note the size or diameter of the wire used and replicate it. Because the mathematics into it is quite involved, and even after calculation, is still need practical adjustments. I imagine your primary bobbin can be separated from the secondary bobbin type, otherwise you will have more works. Don't under-estimate the need to know the wire size and the tightness of the wound, otherwise you will overrun the bobbin because commercial transformers are always compact. If you apply too many tapes, you will overrun it as well.
I made a winding machine [see photo]. But the region I am staying, because we are not rich country like yours, so I still have the benefit to ask manufacturer to re-wind for me at less than US$10 including labour, materials and delivery, neat tidy and the multiple of secondary wires are color coded as well. Though you would not be enjoying this price, but I think you still can try commercial rewinding outlets in your locale rather than winding it yourself.
Cheers! :-+
(https://www.eevblog.com/forum/repair/transformer-winding-insulation/?action=dlattach;attach=301732;image)
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Well my winding questions talked about in this thread. Transformer winding
https://r.tapatalk.com/shareLink?share_fid=25658&share_tid=85231&url=http%3A%2F%2Fwww%2Eeevblog%2Ecom%2Fforum%2Findex%2Ephp%3Ftopic%3D85231&share_type=t
Nice winding Machine by the way. More info on it ?
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