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Electronics => Beginners => Topic started by: [Chrille] on March 03, 2024, 09:22:29 pm

Title: Suitable varistor / MOV for 230V AC power supply?
Post by: [Chrille] on March 03, 2024, 09:22:29 pm
Hi,

I am in the process of designing a DIY power supply that is running on a 230V AC. I would like to add a varistor to the circuit as a safety feature for surge protection, but I am not sure what the specs should be. 230V RMS should equal ~325V peak voltage. Should I select a varistor that is rated slightly higher that the peak voltage like 350V or would a 230V, 250V, 275V or 300V varistor work? How do I know which is the best for my application? What should he energy spec (J) be?

Thanks!
Title: Re: Suitable varistor / MOV for 230V AC power supply?
Post by: Solder_Junkie on March 03, 2024, 10:35:21 pm
See https://incompliancemag.com/new-requirements-for-movs-used-for-surge-suppression-on-ac-mains-ports/

SJ
Title: Re: Suitable varistor / MOV for 230V AC power supply?
Post by: 5U4GB on March 04, 2024, 03:07:24 am
Quote from: Solder_Junkie on March 03, 2024, 10:35:21 pm
See https://incompliancemag.com/new-requirements-for-movs-used-for-surge-suppression-on-ac-mains-ports/ (https://incompliancemag.com/new-requirements-for-movs-used-for-surge-suppression-on-ac-mains-ports/)

Which contains one of my pet peeves, "an MOV".  "An metal oxide varistor"?  Where's David Mitchell with his silenced pistol (https://www.youtube.com/watch?v=qmVnr7rsWrE) when you need him?

Ah, sorry, wrong thread (https://www.eevblog.com/forum/chat/your-pet-peeve-technical-or-otherwise/).
Title: Re: Suitable varistor / MOV for 230V AC power supply?
Post by: Terry Bites on March 04, 2024, 08:24:08 am
Its advisable to choose a MOV 20% above your maximum mains voltage.
See also
www.littelfuse.com/~/media/electronics_technical/application_notes/varistors/littelfuse_selecting_a_littelfuse_varistor_application_note.pdf (http://www.littelfuse.com/~/media/electronics_technical/application_notes/varistors/littelfuse_selecting_a_littelfuse_varistor_application_note.pdf)