question

Hi @Steve Fowler

I very much doubt this is Frequency related. Gensets usually don't even come close to holding a stable frequency, yet you say they usually cure it.

The trouble with being offgrid is that there's no 'infinite' grid to buffer things, so any feedback from the mongrel 'switching' kit within some appliances gets reflected back from a standalone inverter. And then that appliance baulks at some fault in the power quality that it's actually caused itself. Gensets at least have a little spinning reserve that may help counter this.

You'd need a scope to see what's going on, but then would need to also know what to look for as the culprit. The appliance makers won't help. as they'd have to admit their kit is designed only for a grid buffer, and useless without it.

I came across this many years ago with a (non-Victron) standalone inverter and a washer too. I tried adding a 45metre long power lead to the washer, and that dumbed down the power faults enough to let it work.

This may not help you much, but maybe a broadening of your Hz fixation is warranted.. :)

Hi @Steve Fowler . I have read your story with great interest because of the detail you have gone into and the apparent reason for the failing washing machines. I completely agree with JohnC that the frequency shift you mention is not the reason for the problem. A mains frequency variation of 0.5 hz is so minimal that it would have practically no impact at all on the operation of equipment. Even a variation of a couple of hz would not be noticed. As mentioned by JohnC, generators can vary that much without concern.

What is of interest may be the nature of the load presented by the washing machine. I am guessing here but it makes sense that a washing machine runs a motor at varying speed. The method of changing the speed of the washing machine may be to vary the amount of the sine wave presented to the motor, in other words change the duty cycle of the power supplied to the motor. This can be achieved with electronic triggering of mosfets to provide a small amount of power (say only 5 degrees of a 360 degree sinewave ) or a lot of power like all of the sine wave. The multiplus is rated to take a crest factor of 3. That means the peak curent drawn can be 3 times the RMS current drawn meaning quite a distorted waveform but beyond a crest value of 3 the specifications don't say.

The start and stop characterisitc of the sine wave may seem inconsequential but in fact provide an enormous amount of distortion of the current waveform to the load. Fourier analysis can show that say, a square wave has a certain series of harmonic components to make up the square wave. It looks like a square wave in the time domain but it looks like a series of sine waves of varying amplitude at harmonic frequencies (odd harmonics for square waves actually) in the frequency domain. This helps relate to the distorion measurement known as Total Harmonic Distortion (THD). A pure sine wave doesnt have any total harmonic distortion because it only consists of the fundamental frequency (50hz).

As metioned by JohnC the grid has virtually infinaitely low impedance so the very distorted current waveform has little impact upon the voltage waveform. Also, but to a lesser extent the impedance of the generator can handle a distorted current waveform and not suffer too much distortion of the voltage waveform.

The inverter may be a different beast however and when presented with a very chopped and distorted currnet waveform may provide a very distorted voltage waveform that the washing machine may not like. You mentioned a dedicated inverter for the washing machine which is interesting becasue if the original inverter doesn't drive the washing machine load, I cannot explain why a dedicated one would unless the loaded inverter has a distorted voltage waveform but the unloaded inverter has a slightly less distorted voltage waveform.

The washing machine retailers will not know anything about this problem because they are not used to dealing with systems that cannot handle the non-linear nature of the load the washing machine presents. Put simply it is not the washing machine fault. It is a supply issue.

The trick may be to provide some damping of those harmonic distortions. If you had a simple, very basic isolation transformer to feed the washing machine, the inductance of the transformer may just be enough to reduce the harmonic distortion for the washing machine to work. I am not suggesting the isolation transformer is being used for its normal purpose but to merely introduce some inductance into the feed to slightly reduce the harmonic distortion. This is only a suggestion of an idea that could be tried if an isolation transformer is conveniently available.

Very interesting topic, because I have a washing machine from Beko and one from AEG and both have no problems running from 45-55Hz on a MultiPlus-II 25/5000...

However, I just I vestigated the topic a little bit and my conclusion is, that ALL in Europe availlable washing machines are frequency tolerant from at least 47Hz to 53Hz because otherwise the washing machines would stop, if Grid Providers shifting the frequency to stop GTIs overloading the Grid...

Also I so not know a singel GenSet between 2kW and 9,5kW which has a stable 50Hz frequency. The are all shifting between 45Hz and 55Hz and I have never heared of someone which sayed, that his washing machine stop working if it is not exact 50Hz.

I assume, that the error must be somewhere else.

MAYBE the GenSet produce higher voltage?

I had this issue with a rental SDMO HX6000 (230V/6kVA/4,8kW) which outputted 252V instead od 240. My MultiPlus-II is setup to 240V and everything is working PERFECT, but if the HX6000 is connected to charge the Batteries, my Panasonic MicroWave stop working... she simply refuse to work with voltages above 250V.

MAYBE you should check this too.

Have a nice evening

If I understand you correctly the issue is only occur9ing when the batteries are full and the mutli starts to frequency shift upwards to derate the PV inverters you have.

so of cause you could change to DC coupled and this would solve it as then frequency shift is not required anymore.

or if the PV units you have can be controlled by serial or can bus like the Fronius inverters then this is another way to derate them.

Or you could turn off the frequency shift and then setup a assistant to control AC2 out and connect the pv inverters to ac2 out so that when battery voltage raised to say 56v then the ac2 out would open and thus turn the pv units off, this is a heavy handed way of dealing with it though, especially for the pv inverters.

or only do your washing when the batteries are not full