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Old 6th December 2007, 11:45 AM   #1
diyAudio Member
Join Date: Dec 2004
Location: London & Sweden
Default Relay for soft start

I know this simple question might have been covered, but I just can't find a simple answer.

I am building a 5 channel UCD180 amp with total 100000uF and a 1000VA toroidal

Q1: What size of the relay should I go for in the soft start (when the soft start is bypassed by the relay, how much current does it have to be able to draw)?

Q2: What fuse size should I go for?

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Old 6th December 2007, 05:24 PM   #2
diyAudio Member
Join Date: Nov 2007
1000 VA/ 216V should give you 4.63 amp. I chose 216 volt because that would be 240V - 10%

But always keep a safety margin...go for a 10 amp relay.

For fuses, check the devices I2t curves, see a particular example:
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Old 6th December 2007, 06:34 PM   #3
diyAudio Member
Join Date: Dec 2004
Location: London & Sweden
Thanks for great and quick answer!

That was all I wanted to know... until now...

If I have a DPDT relay being able to handle 5A, can I use both of the poles in parallell to get 10A (can a 5A DPDT relay handle 5A per pole)?

THanks again!

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Old 6th December 2007, 06:38 PM   #4
paulb is offline paulb  Canada
diyAudio Member
Join Date: Jun 2001
Location: Calgary
Generally no. Contacts don't share current very well. One opens or closes first. But you could try it if you have one. If you're buying, go for 10A.
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