On 2/10/2014 5:03 PM, Jeff Blaine wrote:
The math is a sideshow. These SSR are getting fried and I'm not sure
the root cause has been laid bare.
Wrong relay for the application? Some sort of TVS or MOV needed?
I've mentioned before, we used 50,000 Joule MOVs across back to back
SCRs. We'd get 2 or 3 guys on the back end of a fork lift to keep the
wheels on the ground when lifting one of these transformers. Not that 3
big men amounted to much compared to the weight of those big forklifts.
They were however enough to just make the difference. In the lowest tap
these transformers were low voltage and "very HIGH" current. How much
is still proprietary, but one could power quite a few luxury homes with
the KVA of one of these transformers..
Typically we'd lose the SCRs AND MOVs if the power didn't reach zero
before switching. The power in that back EMF was horrendous. I don't
know if the MOVs saved any SCRs, but I'd assume so because we kept
buying them. I'll have to put up a photo of the insides of one of the
SCRs. They definitely were not a "chip".
"I would assume" the solid state relays suffer from many of the same
ills these did. Unlike typical MOV installations, these always failed
open, because when they failed, the entire MOV was vaporized. There
weren't even any little pieces to sweep up.
73
Roger (K8RI)
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message----- From: Mike Lucas
Sent: Monday, February 10, 2014 3:34 PM
To: amps@contesting.com
Subject: Re: [Amps] Solid State Relays Again
On 2/10/2014 1:52 PM, donroden@hiwaay.net wrote:
naught times naught equals naught .........
or has that changed with the new math ?
Don W4DNR
Naught times naught is double-naught!----- Jethro Bodine....
Just wait 'till you start doing Gazintas.
Mike W5CHR
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