Solid State contactor or Electromechanical contactor?

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floydR

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Which one to use? What are some of the pros and cons of each type.

Later floyd
 
I use mechanical relays because I've *never* gotten a solid state relay (like these things):
1620314115726.png
to work more than once. The internals will make contact but then 'stick' and not release!!! I've tried 3 of them - maybe they were all fakes
 
I've used Teledyne SSR in beer brewing operations where the controller are pulsing 5500w AC heating elements multiple times per second to maintain certain tempertures. They work great for that but they generate a ton of heat and have to be mounted to a substantial heat sink so they don't overheat and get stuck.

What are you trying to accomplish with a relay?
 
In my case I use them for my Battery Box heating and ventilation system, One reason is the amperage that is allowed esp. with a heatsink.
I use an ESP32 to monitor box temperature and control the SSR's by using a 3.3v relay.
The reason I use relays to control the SSR is that the output of the ESP32 is just not enough to consistently excite the SSR even though they show 3v is enough to trigger them. Not really. So I run 12v through the small relays to excite the SSR and they seem to work consistently that way.
1620315153017.png1620315602322.png
The 2 that I have used so far during the winter to turn on my box heaters have been solid in performance so I guess I got good ones. :p
I will have 2 more that will control the vent fans for the summer.
I suppose an automotive 12v relay would work also but you are limited to 14V were as the SSR is good to 60v.
Wolf
 
I have one like the one OffGrid posted. Seems to work but I have heard about them sticking both mechanical and solid state. I was thinking of going larger the pic I have attacted. Could it work for a relay on a bms to inverter?
Screen Shot 2021-05-06 at 8.35.17 AM.png
 
Fake Fotek VS real Fotek here: https://www.ul.com/node/81246

Fake:
fake_fotek.gif

Real:
real_fotek.gif

I have two DC fake ones. On the AC side, instead, I'll be using a EARU 25A AC contactor to disconnect mains under certain conditions and my choice is simple: I already used EARU products and they never gave me problems plus these contactors are ready to put on DIN Rail. And size is important for me, contactor occupies one space on DIN rail, one of these Fotek SSRs with an adaptor would occupy two spaces. So my choice really isn't really about technology type, although I prefer solid state in general, mechanical is older technology.
 
As I already have several Gigavac contactors(12v control ) and Tyco contactors (12-24v control ) I will most likely use one of them. Just checking out the options.
The one SSR I currently have seems to work I have it on a small 7s10p pack with a 20 amp bms ran the p- line with a switch to -input of the ssr and a line to the positive of battery to + input. no load yet. <yes I needed something to do.>
Later floyd
 
OffGridInTheCity said:
I use mechanical relays because I've *never* gotten a solid state relay (like these things):
View attachment 24910
to work more than once. The internals will make contact but then 'stick' and not release!!! I've tried 3 of them - maybe they were all fakes
Click to expand...
What load were you switching? That is the exact behavior of a AC solid state relay when it tried to switch DC. They rely on the zero crossing point for the triac to disconnect and there isn't a zero crossing in DC. The image you show is also an AC solid state relay.
 
jbotden said:
What load were you switching? That is the exact behavior of a AC solid state relay when it tried to switch DC. They rely on the zero crossing point for the triac to disconnect and there isn't a zero crossing in DC. The image you show is also an AC solid state relay.
Click to expand...
Good info! The picture above was just a quick grab but the ones I tried were 'supposedly' dc. I read that people use these OK, not against them, but after 2 failed attempts I decided to go mechanical contactors - where I can see the contacts in operation. :)
 
The Solid state contactor/relay I posted in 5th post of this thread is rated at 2,000,000 operations which is equivalent to 10 operations per day for 54.74 yrs. The rating which i can't find today was either hours or operations.

Later floyd
 
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