Cheapo Grid Tie Inverter Efficiency Mod - Page 1
Forum section: electronics / general

author: PerpetualWalnut
author_rank: Contributor
timestamp: April 26, 2021, 09:35:35 pm
content: Okay, THIRD time trying to make a new post! Page just reloads with a blank body of text and with no error messages as to why. Do posts need to be approved? If so, then why not indication of that when I click post? Anyways... I'll try again with no pictures attached this time.I bought one of these (1000W Grid Tie inverter Solar with limiter MPPT pure sine wave DC22-60V/45-90V) off ebay a while back. I found that it would run really hot and I was only getting about 80% - 85% efficiency out of it. It's advertised as upwards of 95% efficiency! Yah right! So I tore it down to see what cheap parts they put in it. I looked at the FETs, TRIACS, and Diodes and found them all to be decent except the diodes which were standard diodes rather than high speed Schottky???The diodes they used: RHRP8120https://www.digikey.com/en/products/detail/on-semiconductor/RHRP8120/965460The diodes I replaced them with: SCS210KGChttps://www.digikey.com/en/products/detail/rohm-semiconductor/SCS210KGC/3902856The inverter runs MUCH cooler now and it looks like I'm getting an extra 75 watts of power! I have yet to do an accurate recalculation of efficiency, but based of my estimates and napkin math I'm getting closer to the advertised 90% - 95% efficiency.

author: PerpetualWalnut
author_rank: Contributor
timestamp: April 26, 2021, 09:36:38 pm
content: Pictures...

author: PerpetualWalnut
author_rank: Contributor
timestamp: April 26, 2021, 09:37:11 pm
content: Third times a charm!

author: PerpetualWalnut
author_rank: Contributor
timestamp: April 26, 2021, 09:38:31 pm
content: Back of board.

author: f4eru
author_rank: Super Contributor
timestamp: April 27, 2021, 11:12:14 am
content: People from manufacturing or ignorant devs probably swapped some incorrect parts !

author: nctnico
author_rank: Super Contributor
timestamp: April 27, 2021, 03:26:31 pm
content: Now check EMC compliance... it might be that the design didn't pass with Schottkey diodes...

author: Monkeh
author_rank: Super Contributor
timestamp: April 27, 2021, 03:30:24 pm
content: Quote from: nctnico on April 27, 2021, 03:26:31 pmIt's bold to assume that passed any compliance tests at all.

author: Wolfram
author_rank: Frequent Contributor
timestamp: April 27, 2021, 03:43:22 pm
content: That's quite a dramatic improvement. SiC schottky diodes are close to magic, but at a cost, which is likely why they weren't used originally. EMI is possibly lower as well, due to the lack of significant diode reverse recovery current spikes. These are commonly both a source of significant harmonic energy and switching device losses.

author: PerpetualWalnut
author_rank: Contributor
timestamp: May 06, 2021, 03:16:33 am
content: Quote from: Monkeh on April 27, 2021, 03:30:24 pmIt passed QC didn't it? That's what the QC sticker is for right? RIGHT!?I didn't think about EMC with those diodes, I just figured that they saw that they could get away with cheap diodes in order to cut the cost by $50 - $80

author: Circlotron
author_rank: Super Contributor
timestamp: May 06, 2021, 05:34:39 am
content: Maybe the original sales sample that was sent to the importers had SiC schottkys and later they changed them and kept the cost difference. Probably wouldn't be the first time.