A jig for testing home solar inverters - Page 1
Forum section: electronics / general

author: workshop
author_rank: Newbie
timestamp: June 17, 2015, 06:31:22 pm
content: A couple of years ago, I queried about using a dc power supply in place of a solar array in troubleshooting home solar inverters, most of which, if not all , are grid-tied inverters.The discussion diverted into the more theoretical aspects, like the non-linearity of the V-I curve and so on, without any useful results or conclusion as to how to construct or purchase such a dc power supply.Looking on the Internet recently, there is no much information on this subject. Most of the information revolves around, again, on the theoretical side of emulating the solar panel array with a dc power supply and goes deeply into mathematical equations .. in other words, nothing practical from a technician's point of view.So to keep the objective of this thread as simple as possible. I am interested in troubleshooting inverters from a hardware point of view, that is, if all the components are functional. If they are then the inverter has passed the hardware test.Not a bit interested in the software side for the inverter or testing the inverter to obtain various V-I curves.So, what I am looking effectively is to set up a jig consisting of a dc power supply (suitable for all inverters out there to simulate the solar panel array, that is, set up a particular voltage the panels would be producing and the current that be generated or drawn by the inverter), the inverter under test and connected to the appropriate load, with the objective if a problem is present in the inverter to take voltage readings to determine the cause of the problem.

author: station240
author_rank: Unknown
timestamp: September 06, 2015, 01:37:20 pm
content: I know it's been a few months, but given I'm needing the same sort of thing, I'll put my 2 cents + GST in.1. DC PSU with ammeter , capable of high voltage. In my case 120V to 500V DC.I'm cheating and rectifying the mains to create 400V DC, with circuit breakers/fuses.2. A fake main power source, to create a sinewave the solar inverter will try to sync to.Options are to inject a 50hz sinewave into the LV side of the circuit, or to use say a PC UPS (with safety precautions).3. Dummy load. I've got a oil heater, which is 2200W or so.I've got a 35AMP 400V rated bridge rectifier, large main rated filter caps, big circuit breakers etc. So that's the first part solved via the junk box.Not sure how to approach the second issue, as the UPSs I have aren't sinewave AFAIK.

author: dom0
author_rank: Super Contributor
timestamp: September 06, 2015, 01:40:45 pm
content: Sine oscillator / function generator => audio power amplifier => mains transformer with the secondary driven?

author: wagon
author_rank: Frequent Contributor
timestamp: September 06, 2015, 07:59:29 pm
content: FWIW, I've repaired a couple of solar inverters and tested them 'off grid'. My test rig is a large transformer with 220vac or 110vac outputst, a diode bridge and a big cap. Plenty of fuses too... I used leads with the correct connectors to go straight onto the inverter solar inputs. Works OK for my purposes, since I'm only concerned with repairing the little switchmode supply that runs all the inverter when the sun is shining.

author: station240
author_rank: Unknown
timestamp: September 18, 2015, 02:27:19 pm
content: Finally found a suitable transformer to use as a high current >120V DC supply. It's a massive E core thing with multiple mains and secondary windings.Mains side takes anything from about 100V to 275V by fiddling with the 6 primary wires. The output side is even more silly, with 6 windings all 36V or higher.Found a secondary that outputs 275V DC if I use the entire primary in series. Using a 10amp breaker (which came with the transformer), and 6 amp rectifier as I had those on hand. No filter caps as I don't have bleeder resistors I can use. The inverter has more than enough input caps anyway.The other test supply is a switchmode unit that outputs ~90V DC, it's excellent for testing the inverter's logic/LV supply without supply enough volts to make the main inverter run. Inverter logic runs, and complains about the low voltage. Much safer idea for testing the Inverter's switchmode supply.

author: wagon
author_rank: Frequent Contributor
timestamp: September 21, 2015, 01:43:06 am
content: Quote from: station240 on September 18, 2015, 02:27:19 pmSounds like you've got it sorted. Tune for maximum smoke!