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Forum Index : Electronics : Studer brand inverter with no heatsink!
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Haxby Guru  Joined: 07/07/2008 Location: AustraliaPosts: 423 |
I thought this was interesting and worthy of a post. This is a good quality Studer brand 48v inverter, 5kw continuous. No heatsinks, just two banks of MOSFETs with 64 MOSFETs per bank! That's one way to do it.  Not sure but I think it would have a fan to cool them. The pic was taken from the web. As I get ready to do load tests on my inverter, I'm trying to work out how hard to push my 75 amp rated IGBTs. It seems the thermal calculations for junction temperatures are easy up until a fan is used. The fan cooling can't really be quantified well, so I'll just do some temperature measurements as I go. |
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| oreo Regular Member  Joined: 11/12/2020 Location: CanadaPosts: 49 |
I like it. Very compact and if it blows up, all the fire is contained in a small space :) Greg |
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| Haxby Guru Joined: 07/07/2008 Location: AustraliaPosts: 423 |
I like it too, I guess if it works that's the ultimate test. Imagine having to change all 128 of them with $10 MOSFETs from Digi-Key! |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
Would all them mosfet have to be matched really good to turn on and off a the same time and a high amp mosfet driver needed to drive them all at the same voltage also On pj inverters the more mosfets the lower the voltage gets down the line be warned i am good parrot but Dumber than a box of rocks |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4237 |
Many FET's in parallel gives a good efficiency, due to low resistive losses. But the gate drive power get's enormous. And if you cannot supply that power, your switching losses will counter all the gains in conduction loss. Another thing to realize: A non force cooled TO220 package easilly dissipates 0.5 watt without overheating. So 128 of these could dissipate 64 watt without a heat sink. That alone is 1.3% of the 5 kW. Edited 2021-03-15 06:28 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
A safe way to test an unknown heatsink (with or without a fan) is to bolt one of those gold aluminium metal clad resistors onto it, and test with dc. Its then possible to work out the thermal resistance to ambient. Cheers, Tony. |
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