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Title: S15/S17 20% KVAR energy loss Post by: Extralarstig on February 27, 2020, 08:45:20 AM Hey guys,
while analyzing the efficiency of our farm i noticed a high current running trough our neutral wire (3F+N). Naturally we started checking for any load imbalances but could not find any. Time to get out the old Fluke and start measuring. Turns out the system was producing a lot of (3th) harmonics. 20% of the total load to be exact. which means our generator consumes 20% more gas due to the VAR energy the transformer has to give. Also skin effect is definitely taking place in our cables, but luckily we over-dimensioned. currently we are preforming the same measurements on our farms with S17's because there has been running a big current trough the neutral wire as well. Not a good forecast. My best guess is that the power supply's are distorting the net. Placing a filter could work, but is not very cost efficient. Has anyone else come across this problem? is this because of the Bitmain power supply's? Do other brands have the same amount of harmonics? thanks, Lars Title: Re: S15/S17 20% KVAR energy loss Post by: NotFuzzyWarm on February 27, 2020, 03:48:22 PM High neutral currents is a common problem when running any sort of non-linear load, in this case, scads of switch-mode PSU's. All of them (not just ones from Bitmain) cause it. For powering large farms, using K-factor rated transformers which are designed to accommodate these loads is a must. Ref this from Jefferson Electric (https://jeffersonelectric.com/products/ventilated-transformers/non-linear).
Poking around the Jefferson Electric site I do see that they also carry a line of Harmonic Suppression Systems (https://jeffersonelectric.com/products/ventilated-transformers/harmonic-suppression-system) to use with existing distribution transformers and gensets. Title: Re: S15/S17 20% KVAR energy loss Post by: Extralarstig on March 01, 2020, 10:03:42 PM Alright, thanks for the info!
Title: Re: S15/S17 20% KVAR energy loss Post by: lightfoot on March 09, 2020, 06:33:38 PM Just as a side note: I was wondering about the power factor of Bitmain and Halong supplies. So I went out to the lab today and did a quick check:
The Bitmain 1600 was showing a power factor of .99 (highly aligned) at 1,000 watts The Halong supply from a Dragonmint T1 was showing a PF of .99 as well at 500 watts HP power supplies (700 watt) units I use for testing also show a PF of .99 By comparison a standard ATX supply shows a PF of about .8 and a Gold/80 specification one will show a PF of about .9. I don't know if Bitmain put crap power supplies in the S15's, but I would say it's probably worth your while to pick up a power factor meter and see what a sample of your units are pulling. Because a 20% reactance would indicate some pretty crappy supplies or something else wrong in the setup that could be addressed. Title: Re: S15/S17 20% KVAR energy loss Post by: danieleither on June 28, 2020, 01:23:27 PM Yes - I came across the same problem, and learned the hard way. It resulted in the supply cable for the mining room overheating, which then had to be changed for a larger spec cable. 30m of wasted 50mm 4-core plus labour and downtime.
What's really annoying though, is that during the research phase (I'm very new to mining) I came across a number of other topics on here regarding harmonics from miner power supplies where people had asked if this was an issue to take into consideration, with many reputed forum members dismissing it as nonsense. Title: Re: S15/S17 20% KVAR energy loss Post by: lightfoot on June 28, 2020, 02:16:04 PM Interesting. In your case, what was the source of the problem? I know PF and unbalanced loads can screw up a 3 phase system, did something else catch your mining farm as well?
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