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Enclosure and Ground Pole question

sigma25, sigma26, sigma24

Enclosure and Ground Pole question

Postby Sythrix » October 10th, 2017, 1:14 pm

Hello,

I am currently putting together a σ25 power supply and I am struggling with a couple things. Someone is going to help me with the actual AC wiring, but I wanted to know about some of the materials and have things ready for them. Should I have a wall plug with the 3rd ground pole (USA plug type), or does it not matter? I was reading that this pole is for personal protection on high power devices, so is it even a factor with the σ25?

Also, I was thinking of using the Polycase PM2425 as an enclosure: https://www.polycase.com/pm2425.

Would this be appropriate? I think I can mount on at least 2 of those mounting holes and I want a larger enclosure as more of a heat buffer. I'm using the 62021-P2S02 XFRMR TOROIDAL 5VA transformer: https://www.digikey.com/product-detail/en/acme-electric-amveco-actown/62021-P2S02/TE62021-ND/467640

Thanks for reading!
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Re: Enclosure and Ground Pole question

Postby amb » October 10th, 2017, 4:38 pm

Normally it’s recommended that you use a 3-wire AC cord and connect the ground wire to the chassis for safety. This is for any AC line wiring in a metal chassis, regardless of how high powered it is.

But if you’re going to use a plastic enclosure, then a 2-wire cord is fine because the chassis is isolated. Be sure to use an AC line fuse on the transformer primary circuit,
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Re: Enclosure and Ground Pole question

Postby Sythrix » October 10th, 2017, 4:51 pm

amb wrote:Normally it’s recommended that you use a 3-wire AC cord and connect the ground wire to the chassis for safety. This is for any AC line wiring in a metal chassis, regardless of how high powered it is.

But if you’re going to use a plastic enclosure, then a 2-wire cord is fine because the chassis is isolated. Be sure to use an AC line fuse on the transformer primary circuit,


OK, thank you!

Would a metal chassis provide better noise performance (RFI blocking..?) or is that not really a factor here? I built this with the σ78 so I am looking for the cleanest supply I can manage. If that means using a metal chassis then I'm willing to adapt my plans.
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Re: Enclosure and Ground Pole question

Postby amb » October 10th, 2017, 7:50 pm

For the power supply, it shouldn’t make any difference.
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