I guess if there are no input capacitors in the design then "they" will not wear out due to excessive temperature or ripple current. From an engineering standpoint not the way I would handle it. Does Victron engineering ever post on this forum?
Victron 48/5000/70-95 has achieved UL1741 conformity
- Thread starter JohnWilliams
- Start date
Brucey
Velcro Man
They use a hybrid h bridge design. That thread also gets into calculating DC ripple. Wiring unlimited gets into theory of it and making sure you have sufficient battery and DC wiring. In this particular failure the battery bms failed, wasn't the inverter at fault.
Victron MPII Inverter Overload
There are 4 rows, of 6 each (depending on inverter size). A H-bridge looks like this: Just imagine that for each of the 4 FETs in the picture, you have up to 6 in parallel. In the older allumium-case models you could even see the heatsink/powerpack arrangement looked a bit like an X, with...
energytalk.co.za
1201
Net zero
I like that simplicity for ease of repair but you bring up a good point . I wonder if the ripple is worse than other inverters that have more capacitors
I am familiar with the "H bridge" topology. It is the ideal circuit to synthesize a sinewave in the positive and negative polarity. The FETs are controlled from a high frequency PWM that is fed from a sine reference signal. As the output voltage rises up the sinewave, the on duration of the FETS conduction time builds up to the maximum at the peak of the output waveform, then back down the other side. This creation of the sinewave draws maximum input current at the sine peak and minimum at zero crossing. (consider no output at zero crossing requires no input current, while output at the sine peak requires full input current) This process creates a large 120Hz (2nd harmonic of the line frequency) ripple half sine component in the input current. This half sine of current is drawn through the FET H bridge input stage from the input capacitors. If the capacitors are not present or undersized this current must come from the battery creating an antenna producing radiated emissions from the DC cables. Additionally, the PWM frequency (estimated around 25KHz) ripple current will be present at a lower amplitude. The inverter wants to see the DC input as a low impedance voltage source and containment of this ripple current at the point where it is created is the proper electrical design method. Victron engineering has to be aware of this, but the large capacitors required are not cheap and if not selected correctly their life is limited.They use a hybrid h bridge design. That thread also gets into calculating DC ripple. Wiring unlimited gets into theory of it and making sure you have sufficient battery and DC wiring. In this particular failure the battery bms failed, wasn't the inverter at fault.
Victron MPII Inverter Overload
There are 4 rows, of 6 each (depending on inverter size). A H-bridge looks like this: Just imagine that for each of the 4 FETs in the picture, you have up to 6 in parallel. In the older allumium-case models you could even see the heatsink/powerpack arrangement looked a bit like an X, with...
Brucey
Velcro Man
Given some of these units or their previous models have been working for decades in the field I'm guessing they've done their due diligence.
Given the situation, it is best to keep the battery cables as short as possible, positive and negative conductors adjacent and touching - twisted is best. This will help to reduce radiation and minimize inductance. Be aware this ripple current will be imposed on the battery as a ripple voltage with an amplitude a function of its impedance and the peak-to peak ripple current.
Brucey
Velcro Man
You can monitor DC ripple via a USB to ve bus mk3 cable adaptor connected to a Victron multiplus or quattro inverter.
ricardocello
Watching and Learning
My obligatory ripple threads:
Thread 'Guess what I’m going to do with these capacitors?'
https://diysolarforum.com/threads/guess-what-i’m-going-to-do-with-these-capacitors.95916/
Thread 'Victron Ripple Improvement Testing'
https://diysolarforum.com/threads/victron-ripple-improvement-testing.88093/
Thread 'Guess what I’m going to do with these capacitors?'
https://diysolarforum.com/threads/guess-what-i’m-going-to-do-with-these-capacitors.95916/
Thread 'Victron Ripple Improvement Testing'
https://diysolarforum.com/threads/victron-ripple-improvement-testing.88093/
It would be an interesting exercise to compare the MK3 reading with calibrated lab test equipment. Of course, the inverter does not have direct access to the voltage ripple present on the battery terminals.
Kudos to you ricardocello for being aware of this issue and doing something about it!! You understand the design deficiency and are taking action!! The capacitor ripple current ratings effect on life are specified at the maximum rated ambient temperature. If your ambient temperature maximum is substantially less, you could encroach somewhat on the ripple current rating (it becomes a device life trade off). Or better yet add another one or two caps in parallel.
Brucey
Velcro Man
The risk is excessive DC ripple at the inverter inputs, causing over heating of the input capacitors.
Wiring unlimited goes into this topic in detail, and thats why Victron has prewarnings at 3V and shutdown at 5V of dc ripple, in a 48V system. With sound design of the DC wiring system DC ripple at full load is simply not an issue.
ricardocello
Watching and Learning
Thanks.
My main motivation was to get the ESS/LoM to not glitch on brownouts from the grid, it was really annoying the whole family.
I don’t think H-bridges are unique to Victron. Adding caps should help all inverters.
Honestly, if Victron had not provided ripple warnings and a way to measure the ripple voltage as a built-in feature, I never would have known.
I suspect many other inverters have the same issue, but because nothing is measured or reported, ignorance is bliss.
Until the internal caps fail.
Brucey
Velcro Man
Be aware that adding capacitors can actually make dc ripple worse. Don't try and patch it, figure out the root cause.
ricardocello
Watching and Learning
I’ve measured with an o-scope in multiple locations, including at the inverter DC lugs.
It’s way better. But your point is valid if a resonance with the inductance of the cables occurs.
The root cause is that there is too much total resistance in the path to the batteries,
Or I just need more batteries in parallel. The second thing is way easier to fix, and I will eventually.
Brucey
Velcro Man
Slap some ecoworthy 5kWh rack mounts in there for $800 or so delivered and should be golden,
ricardocello
Watching and Learning
Believe me, I’ve been tempted by all of these cheap battery review threads and Will’s review videos.
I really want to build a battery shed outside the house first, concrete block and small hvac.
These batteries make me worry.
Brucey
Velcro Man
No shame in waiting for block building to be built first, some of these fires are catastrophic.
The root cause is that an AC voltage provider demands current from its source that is directly related to the instantaneous power delivered throughout the entire sine wave cycle. This is an inherent characteristic and the only way to deal with it is filtering. One system design option is to power as many high power loads from DC. Example: water heating or direct EV charging.
1201
Net zero
This conversation is way above my head but this was just posted in another thread today by @RCinFLA and it brings up the question- does the fact that the Victrons have a large transformer help absorb the ripple?
@Solarpete
Post in thread 'Low or high frequency inverter' https://diysolarforum.com/threads/low-or-high-frequency-inverter.99853/post-1355634
@Solarpete
Post in thread 'Low or high frequency inverter' https://diysolarforum.com/threads/low-or-high-frequency-inverter.99853/post-1355634
ricardocello
Watching and Learning
Victron’s design is a hybrid in the sense that they use high frequency AND a toroidal transformer.
Old thread:
Post in thread 'Inverters High or Low Frequency ?'
https://diysolarforum.com/threads/inverters-high-or-low-frequency.6300/post-103169
1201
Net zero
Sorry, is the Victron design different from say xw pro or sunny island? Or do they all work the same way?
ricardocello
Watching and Learning
RCinFLA is by far the expert in this area.
MisterSandals
Participation Medalist
Let's conjure him! @RCinFLA
I have finally come to the realization the MP II 5kVA 48V inverter is really a 4kW inverter before we derate it's output power due to ambient temperature and power factor. Consider 40C ambient operation with a PF of .60, this will give you a 2220W inverter. A PF of .6 is not unreasonable for motor loads like a heat pump water heater or ground source heat pump. This now makes sense the UL cert. document specifies 33A.
The 5kVA rating is based on a specific load condition imposing a crest factor of 3:1, where the current peak is higher by 2.12 times the 1.414 of a pure sinewave. This current peak of 3 rather than 1.414 increases the RMS value of current and the VA.
JeffB1961
New Member
pardon my ignorance . i have no solar/backup and zero experience , but want to get a few decent pieces to to have ..... something ...... and add panels and a mppt in a year or so . i have of course watched Will and a few other youtube folks i see on this forum , watching many several times over as the more i watch the more things seem to make sense .. i think hahaha
anyhow i'm like %95+ shure that i want to start with the victron multiplus ii 48/5000 , but any idea how long till the "new" UL rated versions will be available for sale ? i'm planning on getting the vatrer 48/100 server battery , one to start and at least one more in a year . i will be getting t-fuse , shunt and 275 amp on orr switch for the initial install . at least , thats the plan currently ......
anyhow i'm like %95+ shure that i want to start with the victron multiplus ii 48/5000 , but any idea how long till the "new" UL rated versions will be available for sale ? i'm planning on getting the vatrer 48/100 server battery , one to start and at least one more in a year . i will be getting t-fuse , shunt and 275 amp on orr switch for the initial install . at least , thats the plan currently ......
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