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Forum Index : Electronics : Mini SMD Inverter
| Author | Message | ||||
| kentfielddude Regular Member  Joined: 09/05/2019 Location: United StatesPosts: 89 |
Hello. I am designing a small inverter for testing and experimentation. I have a few questions regarding the design. Do the 10nf snubber capacitors need to be rated at 3Kv? will 1Kv rating be okay?. Also I am not sure where the other two snubber assembly's go. I Still need to add the large caps and the Voltage feedback.  |
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| Solar Mike Guru  Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Snubbers for the inverter mosfets may not be required at all and if required are not generic in that as everyone's inverter is different then so would be the snubbers. I would fire it up at a lower voltage and low power, then use a scope to look at the wave forms across each of the 4 mosfets for voltage spikes that would require snubbing. See this article for calculating suitable values Snubber Calc Hyperlinks on preview screen don't seem to be working.... Cheers Mike |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
[quote]Do the 10nf snubber capacitors need to be rated at 3Kv? will 1Kv rating be okay?[/quote] Just as Mike says, the snubbers are a kind of tuning tool to soak up any nasty switching spikes or ringing. Probably not needed, and the values will be determined experimentally. The thing is, these snubber capacitors may have to carry fairly high peak currents, and so the type of capacitor is just as important as the actual value. By specifying a 3Kv ceramic disc capacitor, it will be a quite large and robust capacitor having low dialectric losses and also capable of high peak current. It will never see anything like 3Kv, but it would be ideal for the job. Something like a small rectangular 10nF 100v plastic dialectric cap would have the same capacitance, and probably sufficient voltage rating, but it will be a small fragile wimpy little part, and may fail fairly quickly if forced to carry very narrow current spikes of several amps repetitively in a very high power circuit.  Cheers, Tony. |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
Ok thanks. Can someone tell me where the two other snubbers should be connected |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Source\Drain, all mosfets in the bridge. |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
 Like this? |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
Correct. only use if required. Those Caps, C1, C2 will be too low a value, I would use 1 x 0.1uf chip ceramic parallel with a 10uf low esr electrolytic in their place, or if running the upper mosfets off isolated psu's use same 0.1uf chip ceramic parallel with a 1uf polypropylene cap. Cheers Mike |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
something like this |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
That would be excellent for main discharge, still parallel it with a 0.1 chip ceramic for the initial HF discharge. Cheers Mike |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
ok thanks this is what I'm thinking the layout going to look like Do you think 63V rating caps will be okay for a 48V inverter?  |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
I can fit the 100v 10000uf caps so I will do that |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
I think me and you and a couple others are the only ones that made it through to the new form I really like this new one I can navigate and go anywhere now the other one I couldn't find anything I used 63 volt caps on a 48 volt inverter until I got some 80 volt ones I'm sure it's not recommended I read somewhere the higher they are above the voltage that's going to be used on them the longer they last I'm sure you was looking for an expert opinion instead of mine You've jumped in head first and you're already climbing up the ladder you did an awesome job on those little boards be warned i am good parrot but Dumber than a box of rocks |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 438 |
Are you going to use heatsinks for the mosfets? |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
Yeah. Mosfet will sit slightly below the board on a heatsink |
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| kentfielddude Regular Member Joined: 09/05/2019 Location: United StatesPosts: 89 |
Will a 15V 1 amp power supply be enough to drive the ir2184s and the arduino nano? |
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