Renewable Energy Questions/Discussion > Automation, Controls, Inverters, MPPT, etc
Inverter Build Project.
rossw:
--- Quote from: welshman on September 26, 2020, 08:03:18 am ---iv'e bought a 100amp solid state relay to replace the standard one.
--- End quote ---
Just a cautionary word.
Check which type of SSR you get. Some have all sorts of electronics to stop them creating switching transients, and they may not turn off when you think they will - so do your homework on their suitability before you put them in line!
welshman:
--- Quote from: Pete on September 26, 2020, 06:04:56 pm ---Sounds like a good plan to swap the relays with a Solid State Relay. There may be a problem with time lag in the relays too.
Just wondering if you are going to put some delay in the SSR relay switching times to match the mechanical relays or whether you think the faster switching will not upset the mosfets more.
Look forward to reading about the build
Pete
--- End quote ---
--- Quote from: rossw on September 27, 2020, 05:03:01 am ---
--- Quote from: welshman on September 26, 2020, 08:03:18 am ---iv'e bought a 100amp solid state relay to replace the standard one.
--- End quote ---
Just a cautionary word.
Check which type of SSR you get. Some have all sorts of electronics to stop them creating switching transients, and they may not turn off when you think they will - so do your homework on their suitability before you put them in line!
--- End quote ---
this is what im using
some of the specs
<10ms on/off time
7.5ma 12v trigger
now there is something else that's interesting about the solid state relay. it only turns on and off at the zero cross point of the sine wave, to avoid surge, rfi/efi. could this be a solution to the charging problem?
rossw:
--- Quote from: welshman on September 27, 2020, 05:38:11 am ---now there is something else that's interesting about the solid state relay. it only turns on and off at the zero cross point of the sine wave, to avoid surge, rfi/efi. could this be a solution to the charging problem?
--- End quote ---
It's exactly this that I'm referring to.
I've seen some of these relays refuse to turn off at all, depending on the nature of their "zero-crossing" detector.
For a giggle, lets hypothetically ask a couple of questions?
Is the zero-crossing based on volts, or current?
If you have a reactive load, current will lead or lag volts, so when volts=0, current will be non-zero.
One would assume that in order to minimise RFI/EMI, it would be switching at 0 *CURRENT*, but most of the ZCD circuits I've seen are zero *VOLTS*.
Depending on the technology in the SSR (and I've seen it happen) - with certain scenarios of load, they simply won't turn off.
Pete:
As you say Ross rarely are loads purely resistive where Volts and Current are in phase.
In an Inductive load the Current will lag the voltage.
I a Capacitive load Current will lead the voltage.
So depending on load the SSR may turn off early or late.
That is one reason I suggested a time lag be built in.
Maybe in some situations a very fast reaction to the mains dropping of is necessary, such as in running a computer with no UPS but otherwise what is a few seconds. Smoke coming from electronics is rarely as easy to fix as the movies show, where they just hit the equipment with a fire extinguisher and it all comes on with no problems. ( learnt that from Lost in Space when I was a kid) never seen it work in real life.
Pete
rossw:
--- Quote from: Pete on September 28, 2020, 01:59:46 am ---As you say Ross rarely are loads purely resistive where Volts and Current are in phase.
--- End quote ---
It gets (potentially) much worse in the situation of switching a generator, and this is one that may slip notice for some - if you have two non-phase-locked signals (such as a free-running inverter and a free-running generator), and lets say they are both "nominally" 240V (in this country that would be the norm), now you have a signal with a peak-to-peak voltage of 340V, and another peak-to-peak also of 340V, and when they're completely out of phase, your relay COULD see the full whack across its input/output. (Depends how things are connected, obviously, but in my case it does apply). You're going to want that silicon to have plenty of headroom!
--- Quote ---That is one reason I suggested a time lag be built in.
Maybe in some situations a very fast reaction to the mains dropping of is necessary, such as in running a computer with no UPS but otherwise what is a few seconds.
--- End quote ---
Lots of electronics stuff won't like more than a few cycles of outage.
Lots of things with compressors will absolutely hate "short duration" outages - half a second, anything up to potentially a few minutes - many will try to re-start a motor with full head pressure, stall and burn out!
--- Quote --- Smoke coming from electronics is rarely as easy to fix as the movies show, where they just hit the equipment with a fire extinguisher and it all comes on with no problems.
--- End quote ---
Ahh yes, movies are a world unto themselves. Any relation to real life is purely co-incidental :)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version