Why no tubing in DER535 Flyback transformer?
The below power integrations App Note shows enamelled copper wire with >500v between them being layed right over each other....
Its concerning a 100-265VAC 60W flyback SMPS
App note DER535
https://www.power.com/sites/default/files/documents/der535.pdf
See page 20 if you wish to... (its also attached).....here you see the switching node wire, which goes up to in excess of 500V, layed right over the wire that connects to primary ground. There is no tubing. Its just bare enamelled copper wire. It shows that enamelled wire has superb strength?
If you look at other pictures there...you see other cases of High voltage being layed (touching) over low voltage wires.
The switching node wire is 0.32mm diam, and the pin 3 (gnd) wire is 0.2mm diam....and yet their enamelled insulation is good enough to handle the 500V thats between these wires?
On the same page, if you look at pins 5 and 6, there you see the mid-primary point wire, lying right over the bias coil voltage wire....again...no problem?
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Also, the primary finish is several lavers above the primary start, so that the wires only appear to touch. Having said that, the lead dress on the primary start lead could have been better, avoiding the appearance of the wires touching entirely. I had a meeting with the assembly techs that generate the figures for these designs a few days ago and instructed them how to properly dress the primary start lead to avoid this situation.
Hi treez,
If the wires accidently got scratched, there will be problem. Since this is just a reference design, actual power supply design can try to avoid it if needed or add tubing as you stated as additional safety insulation.
Regards,
Jedidiah