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Old 17th July 2012, 08:34 PM   #21
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by tauro0221 View Post
Hi,
What about using the MOC3061. This will power up the amplifier clean since it is start at zero crossing of the AC. Attached it is the technical data. Also you can use a zero crossing relay Omron G3NE-220T-US. I found it no too long ago I am planning to using it in my new design.
Very useful devices are the opto-triacs. I used one to directly power a (small) transformer. Works brilliantly. Power is applied when audio is present and has a 5 minute switch off timer when audio finishes.

On the subject of zero crossing switching. Switching a large toroid at the zero point can actually be the worst condition for generating a large inrush current. How large depends on how much residual magnetism is left in the core (which depends on where in the cycle it was switched off). It's better to apply power at the peak of the mains cycle... which goes against initial logic.

I believe once large reservoir caps are added into the equation all that goes out of the window though, and the inrush current is large whatever point in the cycle the transformer is switched. Haven't seen much info on that anywhere.
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Old 17th July 2012, 09:57 PM   #22
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Hi,
I am using the Omron SSR in my 400VA toroid transformer and I am not noticed the inrush current. Maybe I need to read the current to verify it but what your are saying it is true.
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Old 18th July 2012, 05:30 AM   #23
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NEVER switch a transfomer at zero crossing. There is a long thread explaining the reasons. But I am 200% sure of my statement.

Gajanan Phadte
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Old 18th July 2012, 06:09 AM   #24
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Could you give a link to the thread explaining that, after a quick search just now I couldn't turn up any info on it.

Is it only an issue for larger transformers since they will have the most significant inrush condition? I have some smaller transformers (less than 50VA) and smps that I was going to sequence with SSR with zero crossing switching so I am interested to learn more.
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Old 18th July 2012, 06:30 AM   #25
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Hi,
I did the test with the SSR and without and the amps when to 3.2 amps in both test and them drop to 1.7 amps. I didn't see any difference. My transformer it is a 400va with 40volts.
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Old 18th July 2012, 07:01 AM   #26
RJM1 is online now RJM1  United States
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Beware of Zero-Crossover Switching of Transformers
http://relays.te.com/appnotes/app_pdfs/13c3206.pdf
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Old 18th July 2012, 07:53 AM   #27
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It seems that a simple relay is the go. If I was to use a relay. Nice notes on the zero crossover problems, until i read that article i was contemplating using one. I have been reading about triacs they do seem to be a bit noisy unfortunately.
I have been enjoying everyone comments I have been learning quite a bit.

Cheers
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Old 18th July 2012, 08:10 AM   #28
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Hi,
I think the best solution it is the use of a simple and cheapo switch. Making it fancy create more problems. But also here in this link they have an application note page 7 that it is said that the best solution in this case is to fire the traic at the peak or at 90 degree to eliminate the problem. Here it is the link:
http://www.fairchildsemi.com/an/AN/AN-3004.pdf
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Old 18th July 2012, 09:21 AM   #29
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Thank you tauro,
I think you are right, a good quality switch is what I need the KISS (Keep It Simple Stupid) principle

cheers
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Old 18th July 2012, 10:16 AM   #30
RJM1 is online now RJM1  United States
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You could mount the switch in the back and use use a long shaft to the button on the front panel.
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