Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 48 replies
  • Subscribers 32 subscribers
  • Views 3438 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Ever thought about ... ?

gkenyon
I was asked a series of interesting questions this week about fault protection and overload protection for a particular application. Some of these really make you think, and the physics doesn't always lead you where you think you'd go.


Dropping out of all this, was me pointing out something interesting which I wonder whether it's ever crossed the minds of contributors to this Forum ... so here goes.


Ever thought about what, in typical UK installations, protects the electronics in a plug-in [to a standard BS 1363-2 socket-outlet] phone charger / wall-wart type power converter against:

(a) Fault current (consider both cases of L-N and L-PE); and

(b) Overload current ?




Parents
  • 0
    Your analysis of the transformer design may be correct Mike, but the "excuse" that it needs this capacitor to save a small number of pennies is not satisfactory. The interwinding capacitance of this transformer could be designed to be a few pF, and the leakage inductance small with a slightly different philosophy, but I admit it would be slightly more expensive. When I buy a product that costs the best part of £1000 or so I do not expect someone to have made it less safe for the cost of pennies. That is the real point I was making, and it is important. Fitting two capacitors in series is a bodge, if one may fail, so may two! Tingles are unacceptable for a class 2 device, however it measures. It is also worth realising that class Y capacitors are not cheap.
Reply
  • 0
    Your analysis of the transformer design may be correct Mike, but the "excuse" that it needs this capacitor to save a small number of pennies is not satisfactory. The interwinding capacitance of this transformer could be designed to be a few pF, and the leakage inductance small with a slightly different philosophy, but I admit it would be slightly more expensive. When I buy a product that costs the best part of £1000 or so I do not expect someone to have made it less safe for the cost of pennies. That is the real point I was making, and it is important. Fitting two capacitors in series is a bodge, if one may fail, so may two! Tingles are unacceptable for a class 2 device, however it measures. It is also worth realising that class Y capacitors are not cheap.
Children
No Data

Community Rules & Guidelines