Toroidal fusr ratings.

seroxatmad · 18th October 2009, 09:53 AM

Hi

I am using a 230v 30va toroidal with 0-12v, 0-12v wired for 24v output.

The secondary fuse is a TD 1.25A but at present am using a 0.625A for the primary. Is this to high?

Cheers

John

richie00boy · 18th October 2009, 11:58 AM

I = P / V
= 30/230 = 0.13A

So yes it is too high. Secondary fuse is ok though, could even be a touch higher if you want to draw full rated power from the transformer.

peranders · 18th October 2009, 03:05 PM

You have inrush currents so approx. 1 A slow is OK I should think but you could test with 630 mAT also maybe.

seroxatmad · 18th October 2009, 04:23 PM

Hi

Thanks for the replies

Its the transformer for a millett max headphone amplifer. The 30VA is a little over rated, but anything less than 1.25A blows in the secondary.

At present i am using a .635A in the primary - but i will change it ASAP.

Cheers

John

richie00boy · 18th October 2009, 08:23 PM

You might need a soft start or a slightly higher rated time delay fuse, in the primary. I prefer soft starts

18th October 2009, 09:53 AM	#1
seroxatmad diyAudio Member Join Date: Dec 2006 Location: Durham, UK	Toroidal fusr ratings. Hi I am using a 230v 30va toroidal with 0-12v, 0-12v wired for 24v output. The secondary fuse is a TD 1.25A but at present am using a 0.625A for the primary. Is this to high? Cheers John

18th October 2009, 11:58 AM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I = P / V = 30/230 = 0.13A So yes it is too high. Secondary fuse is ok though, could even be a touch higher if you want to draw full rated power from the transformer. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

18th October 2009, 03:05 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	You have inrush currents so approx. 1 A slow is OK I should think but you could test with 630 mAT also maybe. __________________ /Per-Anders (my first name) or P-A as my friends call me

18th October 2009, 08:23 PM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	You might need a soft start or a slightly higher rated time delay fuse, in the primary. I prefer soft starts __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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18th October 2009, 04:23 PM	#4
seroxatmad diyAudio Member Join Date: Dec 2006 Location: Durham, UK	Hi Thanks for the replies Its the transformer for a millett max headphone amplifer. The 30VA is a little over rated, but anything less than 1.25A blows in the secondary. At present i am using a .635A in the primary - but i will change it ASAP. Cheers John

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