Electronics > Beginners
power input for small transformer, good practice
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IvoS:
I will have a small linear power supply with this 10VA or similar transformer https://www.mouser.com/ProductDetail/Bel-Signal-Transformer/14A-10R-28?qs=sGAEpiMZZMvwUzoUXIIvyd9mRDTtMBVeVfiyOmBntwwckc0OwNq22Q%3d%3d
Bridge rectifier, caps etc. on secondary side followed by low noise LT1963 (or similar) regulators.
What else besides a fuse should be on the primary side of the transformer? MOVs? spark gaps? ........ Low noise power supply is my priority. Thanks.
exe:
I'd put a fuse :). Also EMI filter of lowest current rating possible as those have bigger inductance and, presumably, filter better. They also come at least in two flavors: normal and medical. I don't remember the difference, but you can google it.
IvoS:
Fuse will be there definitely. I want to put MOV on the AC line. How do I size it for 120V?
exe:

--- Quote from: IvoS on June 27, 2018, 08:02:33 pm ---How do I size it for 120V?

--- End quote ---

I dunno :(. But for sure it must be rated higher than 120V*1.1*1.41 (nominal voltage * 10% variation * peak sine value).

I didn't put a MOV because I decided it's not necessary. Transformer itself is quite robust to transients.
Cerebus:

--- Quote from: exe on June 27, 2018, 08:52:41 am ---I'd put a fuse :). Also EMI filter of lowest current rating possible as those have bigger inductance and, presumably, filter better. They also come at least in two flavors: normal and medical. I don't remember the difference, but you can google it.

--- End quote ---

Medical filters have low earth leakage currents, which in practice usually means no Y capacitor(s) between the phases and earth.
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