Inductive Limit Switch problem

[Kitwn]

The weirdest things can happen with EMC issues, at 6Mz a couple of bits of wire running parallel for a few m probably makes a half decent transformer

This picture shows the output coupling transformer of a Marconi BD272 AM short wave radio transmitter rated at 250KW (that's a whole Megawatt peak output). I cut my teeth on these things in the 80's. All that power is being coupled through this single turn, air spaced transformer. These are the coils for 15MHz I think, but the 6MHz ones are not much bigger. The peak voltage across the primary turn is about 40KV even though it looks remarkably like a short circuit to the uninitiated.

No chance of that for me either - 'coz of the virus they've been shut here for over 2 weeks

Same here. The local microbreweries are doing canned takeaways though, so I can still enjoy my favourite local brew at much less than the in-a-glass price they charge if you sit on an old wooden chair in their gravel yard getting swamped by midgies and other people's children. You have to look on the bright side!

Western Australia has now closed it's borders to all non-essential travellers and travelling between different regions within WA without a good reason can cost you $50,000.

[Voicecoil]

This picture shows the output coupling transformer of a Marconi BD272 AM short wave radio transmitter rated at 250KW (that's a whole Megawatt peak output). I cut my teeth on these things in the 80's. All that power is being coupled through this single turn, air spaced transformer. These are the coils for 15MHz I think, but the 6MHz ones are not much bigger. The peak voltage across the primary turn is about 40KV even though it looks remarkably like a short circuit to the uninitiated.

Thanks for posting that - awesome bit of kit even if it looks completely illogical to the uninitiated!

[Kitwn]

Thanks for posting that - awesome bit of kit even if it looks completely illogical to the uninitiated!

This machine is 1960's technology. Some of the later, higher power designs, have water cooled the coils. A key difficulty with those was how to clamp the plastic water pipes onto the copper coils. Metal jubilee clips glowed white hot as soon as we switched the bloody thing on and plastic clips went brittle in about a week. We ended up using waxed cotton whipping cord, similar to to an old fashioned cricket bat handle. It's surprising the skills I had to learn as a BBC Transmitter Engineer back in the days when it was still fun.

[cropwell]

This machine is 1960's technology. Some of the later, higher power designs, have water cooled the coils. A key difficulty with those was how to clamp the plastic water pipes onto the copper coils. Metal jubilee clips glowed white hot as soon as we switched the bloody thing on and plastic clips went brittle in about a week. We ended up using waxed cotton whipping cord, similar to to an old fashioned cricket bat handle. It's surprising the skills I had to learn as a BBC Transmitter Engineer back in the days when it was still fun.

Bet it made instant toasties. Seriously though, was all that RF energy hazardous to workers ?