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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
yeah it will be at 50kHz so 1.7-3.3 for a dielectric constant is what i expect, so what ever my dry winding capacitences are, they will more than triple once vacuum-oil drawn. i will use Envirotemp FR3 fliud, the soy bean one is super good for dielectric strength, 57kv/mm, and 0.0005 for Dissipation factor. also, my max field intensity is designed to be 17kv/mm.
so,
Envirotemp = 57kv/mm breakdown, 3.2 dielectric C, 0.0005 for DF. Canola oil = 45kv/mm breakdown, 3.0 dielectric C, 0.0065 for DF. PVC plastic = 29kv/mm breakdown, 2.9 dielectric C, 0.1000 for DF. <- (DF, yikes!) mineral oil = 40kv/mm breakdown, 2.2 dielectric C, 0.0005 for DF.
-Patrick
Well done, Patrick, and thank you for drawing attention to the global need to switch over to environmentally friendly dielectric oils.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yeah i dont see the need to use hydrocarbon oil, and i only have "special disposal" once per year in california.. with food oil you buy it, use it, then you can put it down the sink. with hydrocarbon mineral oil, your utilsles and workspace get splattered too, with bio-oils you just use soap and water. then wash the rest down the drain. soy bean seems best, but its special, canola is next best and is common at the supermarket.
Soybean oil is proposed as a dielectric fluid in several patents, eg US Patent 6613250:
which also describes techniques for slowing the degradation of the oil through the use of oxygen scavengers, an inert gas headspace, anti-microbials, and so on.
Added to the problem of 'gumming up' by oxidative polymerization is the complication of soybean oil's large change of dielectric constant with temperature, so the only reason for choosing soybean oil, over, for example, yellow olive oil, which has none of these disadvantages, is economic.
Raw soybean oil is a cheap industrial feedstock, so it is worthwhile developing processes to make it suitable as a dielectric fluid, while it could never make economic sense to use yellow olive oil, despite its superior dielectric properties.
Soybean oil is proposed as a dielectric fluid in several patents, eg US Patent 6613250:
which also describes techniques for slowing the degradation of the oil through the use of oxygen scavengers, an inert gas headspace, anti-microbials, and so on.
Added to the problem of 'gumming up' by oxidative polymerization is the complication of soybean oil's large change of dielectric constant with temperature, so the only reason for choosing soybean oil, over, for example, yellow olive oil, which has none of these disadvantages, is economic.
Raw soybean oil is a cheap industrial feedstock, so it is worthwhile developing processes to make it suitable as a dielectric fluid, while it could never make economic sense to use yellow olive oil, despite its superior dielectric properties.
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About Bio-Oils for HFHV Transformers.
