Took LG washer off generator. Running off panels, no battery

[OperaHouse]

Did my first laundry today running off solar panels. No battery needed.  For those days when it is sunny.  Panel voltage fed directly into a MSW inverter using only the H bridge section to create AC. We only do laundry when it is sunny anyway as it has to be line dry. I can't get used to not hearig the generator run!

[DamonHD]

Fascinating!

What's the DC voltage range / tolerate of the H-bridge section, do you know?

Rgds

Damon

[OperaHouse]

It is one of the high capacity LG direct drive washers. Usual washing is about 200W with spin getting about 400W. This was just a preliminary test and wasn't sure it would get as far as it did. Voltage is at the very low end at 115V DC. Normally a MSW inverter would have 140V DC.  Line voltage of 120V would give close to 160V on the VFD capacitors.  At lower voltage the VFD just draws more current so I will be adding  two12V panels in parallel to boost it up another 18V.  Inverter I believe has 200VFET.  I haven't even added extra capacitors yet to the inverter to cover extra surge currents. I switch two 60V grid tie panels in series with the other 60V array. Normal summer heat drops that to about 55V per panel.  I dump power over power point into a water heater for the house and I have an additional water in the garage I will be connecting up.  Currently I run out of the ability to dump all my power. Might as well have warm water for washing and limiting any over voltage.

[Artful Bodger]

Yep, it's nice to hear the washing machine and not the generator. I repaired a 3kVA inverter just to run the washing machine as the surge from my cheapo washing machine would easily hit 20A and trip my small inverter.
It had never occurred to me to just run the panels straight into the inverter, mainly as we often get passing clouds living so close to the mountains. I might have a play!

[OperaHouse]

The real trick here is this is a MSW inverter and I feed 120 to 160V DC right into the H bridge. I just added a 12V array in series because 120V DC is barely enough to run the machine and with a higher voltage it will draw less current, win win for the array. And at only 3A it is not much of a load for most arrays.

Interesting thing about the H bridges in these older non microprocessor designs.  They don't care what voltage you feed into them.  I've run this one as a test on just 24V.  That means you could use just a couple grid tie panels and a boost auto transformer to run aeriator pumps with no battery.  Most fractional HP AC motors are impedance protected so you can brown them out a little.

[SparWeb]

Wow.

More details please?  I have a MSW inverter sitting on a shelf, forgotten since I got a pure-sine years ago.
Are you saying I can bolt "anything" the the H-bridge and get AC without also producing magic smoke? 
(Within reason?) 
(what's reasonable when doing this?)

[OperaHouse]

Yup, this is the real story.  Find the high voltage capacitor, run wires out for  + and -, and run any voltage in up to 140V. I'd suggest using at least 24V because of the way they might be bootstrapping the high drive.

The control electronics still has to be powered.  The MSW inverter must have an on off switch, not momentary. Locate the side that doesn't go to the 12V terminal.  Supply 12V to that side and it will require around 50ma.  As long as that voltage stays in reason, the inverter will keep running. I ran a 50W 24V lamp on 20V.

This has possibilities. Many small AC motors are impedance  protected so they can be browned out a bit.  With a 60V array, you could use a boost transformer to get 120V and run 90-130V for example.  Still must be some considerations for turning it on and off at low voltage

[OperaHouse]

I should note that this should work with all older MSW inverters with a common negative between input and output caps without microprocessors which have more sophisticated fault detection.  The one I used had another unique feature.  With a little under 120V DC I was getting a reading of 113V RMS.  When I added the extra 18V from the additional 12V panels, it went up to 119 RMS.  Immediately I thought those panels weren't producing.  There was nearly 160V DC with no load.  Apparently as part of the regulation the duty cycle reduces as voltage goes up.  I don't think this is common.