I have an old Phoenix 24/3000w inverter, but am now looking to upgrade to a much more powerful 48 V model. I have a question for the community:
I reported an issue with my Phoenix inverter to Victron several years ago. When my wife uses her (not cheap) GHD hair straighteners, the inverter vibrates loudly at around 6 Hz. It sounds like a muffled hammer drill.
This is not because the GHDs are using more power than the inverter can supply . It’s because the GHDs, like many other small appliances, use a Thyristor or Triac to implement phase angle control.
Just to confirm this, I wired a standard household light dimmer switch (which also uses phase angle control) in series with a 100w tungsten filament light bulb, and connected this circuit as the only load to the inverter. As I adjusted the brightness of the light, the inverter made a lot of loud banging noises and its power output was choppy. When I added a diode in series so that only one half of the AC cycle would be used, it was even worse.
When I added my fridge to the inverter with the circuit above still connected, the fridge light flickered and its compressor sounded ill. The voltage being supplied by the inverter was way out spec, and I’m sure after a while that the fridge would have suffered.
I surmised that there is protection circuitry in the inverter that is comparing power within each cycle - probably related to detecting high inrush current from inductive loads - to determine if there is some kind of instantaneous overload. And that the chopped up sinusoidal waveform was triggering this.
I’d like to know if this issue is still there on more modern descendants of the Phoenix model. I’m not asking about HF inverters, but those that use big toroidal transformers to provide a high peak power surge capacity.
@LX - Does the Multi not suffer the same issue? I don’t need a charger, but I’d consider it if it can handle non-linear loads. Are you recommending it on the basis that you know it doesn’t exhibit the behaviour above?
The Inverter RS is of less interest. It’s an HF design - which I said wasn’t interested in, due to its relatively low peak power multiple.
I’m sure we could have an interesting debate about dimming approaches - but of course I only used that simple dimmer circuit as it implements the same phase angle control approach as GHDs do. Although there is an argument that phase angle control has benefits over zero cross…
I use a Crydom PMP series proportional solid state relay, to make a power diverter for a resistive water heater. The heater is nominally 3kW. The SSR does zero cross phase angle control.
I have used this this successfully on both a 5kVA Multiplus 2 and the Multi RS. No light flicker or inverter issues.
Interestingly, burst mode (which used full cycles, but intermittent) did cause flickering.
@Deon Korb - Thanks. This just reinforces my suspicion that phase angle control causes a problem. If my load was relatively large, I can understand how switching it on mid-way thru an AC cycle might cause transients and harmonics. But in my test scenario I’m only switching up to 100 W of resistive load connected to a ~3000 W inverter. Something in the inverter doesn’t like this.
Some consumer electronics companies have decided to use phase angle control in their hair straightener or coffee machine products. When I upgrade my inverter, I want to select one that isn’t going to have an issue with them.
Yes, I suspect they use leading edge. It’s still popular, unless you are dimming LEDs. But it’s not just cheap products that use it. Consumer electronics manufacturers assume a mains supply, where any non-linear load characteristics are absorbed by the grid. They tend to use proven technology, and don’t design for an inverter-based supply.
Yes, they are all HF for the PWM stage. But while Victron markets the Phoenix inverter as having hybrid HF technology , it markets the Inverter RS just as an HF inverter.
Don’t want to get stuck on semantics. Here’s the point:
My old Phoenix 24/3000 inverter has a peak power output of 6 kW I think, against a continuous output power of 2.4 kW @25 deg C. That’s a 2.5x multiple. The Inverter 48/5000 is also 2.5x. From memory this peak power is available for around 30 secs.
The Inverter RS 48/6000 has a peak power of 9 kW for 3 secs, and 7 kW for 4 mins, against a continuous output of around 5 kW. The multiple is lower. It only weights 11 kg, compared to the Inverter 48/5000 which is 30 kg – the bulk of which is the toroidal transformers.
I need the 2.5x multiple that the Phoenix provides, both to handle inductive loads starting up and for multiple loads active at the same time.
This problem (inverter running out of spec when supplying a phase angle controlled load) was being reported on Phoenix inverters 7 years ago.
My post is asking a question: Do Victron’s newer inverters with a high peak power multiples (the heavy ones) still exhibit this issue? @Ludo has suggested they do.
Does anyone know what causes it? Bear in mind my test circuit used a relatively small 100 W resistive load.
It has to do with the working mode. With or without AC-IN connected.
Also it has to do with the mechanism for the regulation of the output voltage and how is it made.
How the output voltage is collected, filtered and read back. And how it’s processed.
More, it has to do with the way the AC-IN is followed and synch with when AC-IN is connected.
Of course, it can be masked to a point by modifying a little the firmware which works for single phase, non parallel mode, but will mess things up when parallelizing and using in a 3 phase environment.
For more, I would rather let an Victron engineer to explain, to not enter into details of publicly show schematics, reverse engineering & co.
@Alex - Thanks. I have a plain inverter, not MP. So no AC IN. And I was planning to run 2 inverters in parallel.
I understand you feel you cannot share proprietary schematics or know-how. That’s understood.
When a voltage is step-applied to the input of the output transformer at 100 Hz, this will generate harmonics/ringing and back EMF. Can you comment on whether one of these is the root cause, and if so which one, rather than how the inverter works?
I did try and get an answer out of Victron years ago, without any success…
Sorry Alexandra if I seemed out of line… It was not intentional.
Probably the language is in a degree a barrier.
As my old father says, listen more and speak as less a possible, as the mouth is beating the buttocks… I’m still learning…
