Solid State Relay Experts - Please Come In
They should still pull the same current but for only half the time so RMS current will be significantly less. If you looked at the current on an oscilloscope you should see peaks close to the same assuming the pump can draw the current in the short time it has while in the "on" state. Sometimes if the frequency is too high it never really shuts off completely. Using a fluke multimeter or split core current clamp will only tell you average current.
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Joined: Nov 2003
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From: Norn Iron
Ultimately RMS will be fine but I have a current clamp meter and a cheap crap Hantek USB scope and clamp so will be trying both.
Ultimately average is all that matters for continuous load purposes, heat etc ?
Not sure if it really matters to the SSR about frequency in this respect ? Crydom state it can run at 1k...so would there be any survival issues running at this vs a lower frequency ?
Although all seems fine and quiet at 850
Ultimately average is all that matters for continuous load purposes, heat etc ?
Not sure if it really matters to the SSR about frequency in this respect ? Crydom state it can run at 1k...so would there be any survival issues running at this vs a lower frequency ?
Although all seems fine and quiet at 850
I don't expect you to have any problems cause you heat sinked the crap out of it lol, but just for conversation's sake, the higher the frequency and peak currents can cause the delta T to rise over time (basically slowing heating/cooking itself). I haven't looked at the guts of that particular SSR so not sure if its opto based or FET based, but the higher the switching frequency and the larger the current the hotter the FET will run, hence the need for more heat dissipation.
Just glanced at their website and picked a random panel mounted series and they have derating curves based on ambient temp and load, you might take a peek at your specific one just in case.
Just glanced at their website and picked a random panel mounted series and they have derating curves based on ambient temp and load, you might take a peek at your specific one just in case.
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Joined: Nov 2003
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From: Norn Iron
This is the one I fried, not specifically their DC series, but specs seem to read the same.
Again I believe this was largely caused by a short on the load side because of how I fitted the flyback diode ( wiring insulated melted when I heat shrinked it. )
https://uk.rs-online.com/web/p/solid...elays/3939377/
I'd assume the internals of that one and my current one would be similar ?
https://uk.rs-online.com/web/p/solid...elays/7569528/
Again I believe this was largely caused by a short on the load side because of how I fitted the flyback diode ( wiring insulated melted when I heat shrinked it. )
https://uk.rs-online.com/web/p/solid...elays/3939377/
I'd assume the internals of that one and my current one would be similar ?
https://uk.rs-online.com/web/p/solid...elays/7569528/
Per their datasheets, their equivalent circuits are nearly identical except 1 has the LED indicator that you're driving the input side. Minor variances in specs. One thing that comes to mind, if you want some badass thermal paste to transfer the heat better, take a look at Arctic Silver. It was a HUGE improvement in some designs I've worked on when it comes to getting the heat out of the part and into the heat sink.
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Verdad Gallardo I think in 1 design we saw a 5-8*C drop in component temps changing from a thermal pad to arctic silver...so I would assume going from bare metal to metal to a thermal compound would be even more.
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From: Norn Iron
Oddly looking through some Crydom stuff last night, I noticed in specs for their PowerPlus DC series...whilst the low current SSR's seem to be rated to 1kHz....their 100A is only 700Hz, with a similar pattern in between
10/20A 1kHz
40/60A 900Hz
80/100A 700Hz
I think when I fried mine I might have had it at 950Hz ? Cant remember ( although my wiring was still damaged via melted insulation and sure that was my fault )
I only noticed as I was ordering a spare last night and decided to opt for the 100A version in case I need to run the 3 pumps in the future, wanted ample capacity.
10/20A 1kHz
40/60A 900Hz
80/100A 700Hz
I think when I fried mine I might have had it at 950Hz ? Cant remember ( although my wiring was still damaged via melted insulation and sure that was my fault )
I only noticed as I was ordering a spare last night and decided to opt for the 100A version in case I need to run the 3 pumps in the future, wanted ample capacity.
Couple things....
FETs have what's called an Rds on....it's the internal FET resistance between the source and drain. There are limitations of how low this can be compared to how much current said FET can source or sink. Typically the higher the current capacity of the FET, the higher the Rds on....which creates heat because the FET has to dissipate this power.
FETs do NOT like being in the linear region, they want to be saturated. Everytime you turn the FET on or off you momentarily traverse this linear region, which builds up heat. The higher the frequency the more traversing of this region.
Both of these things combine to limit what these SSRs can do.
FETs have what's called an Rds on....it's the internal FET resistance between the source and drain. There are limitations of how low this can be compared to how much current said FET can source or sink. Typically the higher the current capacity of the FET, the higher the Rds on....which creates heat because the FET has to dissipate this power.
FETs do NOT like being in the linear region, they want to be saturated. Everytime you turn the FET on or off you momentarily traverse this linear region, which builds up heat. The higher the frequency the more traversing of this region.
Both of these things combine to limit what these SSRs can do.