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Q&A Flyback transformer with Intrinsic Safety

I am also not an expert, but have been working on designing a couple of products that need C1D1, C1D2, and some IS associated apparatus with some electronics consultants that specialize in these ce...

posted 2y ago by Hawk2020‭  ·  edited 2y ago by Hawk2020‭

Answer
#2: Post edited by user avatar Hawk2020‭ · 2022-10-21T22:47:45Z (about 2 years ago)
  • I am also not an expert, but have been working on designing a couple of products that need C1D1, C1D2, and some IS associated barriers with some electronics consultants that specialize in these certs.
  • I assumed the zener power calculation would be what you did when designing an IS barrier for a C1D2 main board; however, CSA at least, actually does it like this:
  • ![Zener Calculation](https://electrical.codidact.com/uploads/MNHyU1hj1JMLexWHhHXw8MhC)
  • Since you end up with giant expensive Zeners with that math, I ended up using SCR crow bars:
  • ![IS Schem](https://electrical.codidact.com/uploads/JwBQks85JVi5Ajmtk2NzSrfL)
  • The 2mm thickness on the bold parts is to make them infallible (so they can't short them out for the test from my understanding). Not sure if you ended up going this way, but hopefully this is useful to someone. Can't really show the entire schematic for legal reasons, but I could answer some questions if it would help.
  • I am also not an expert, but have been working on designing a couple of products that need C1D1, C1D2, and some IS associated apparatus with some electronics consultants that specialize in these certs.
  • I assumed the zener power calculation would be what you did when designing an IS barrier for a C1D2 main board; however, CSA at least, actually does it like this:
  • ![Zener Calculation](https://electrical.codidact.com/uploads/MNHyU1hj1JMLexWHhHXw8MhC)
  • Since you end up with giant expensive Zeners with that math, I ended up using SCR crow bars:
  • ![IS Schem](https://electrical.codidact.com/uploads/JwBQks85JVi5Ajmtk2NzSrfL)
  • The 2mm thickness on the bold parts is to make them infallible (so they can't short them out for the test from my understanding). Not sure if you ended up going this way, but hopefully this is useful to someone. Can't really show the entire schematic for legal reasons, but I could answer some questions if it would help.
#1: Initial revision by user avatar Hawk2020‭ · 2022-10-21T22:46:46Z (about 2 years ago) 
I am also not an expert, but have been working on designing a couple of products that need C1D1, C1D2, and some IS associated barriers with some electronics consultants that specialize in these certs. 

I assumed the zener power calculation would be what you did when designing an IS barrier for a C1D2 main board; however, CSA at least, actually does it like this:


![Zener Calculation](https://electrical.codidact.com/uploads/MNHyU1hj1JMLexWHhHXw8MhC)

Since you end up with giant expensive Zeners with that math, I ended up using SCR crow bars:

![IS Schem](https://electrical.codidact.com/uploads/JwBQks85JVi5Ajmtk2NzSrfL)

The 2mm thickness on the bold parts is to make them infallible (so they can't short them out for the test from my understanding). Not sure if you ended up going this way, but hopefully this is useful to someone. Can't really show the entire schematic for legal reasons, but I could answer some questions if it would help.