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Hello: I have two 10KW 48V input 240 split phase LF powerjack inverters. I'm looking for any information on how to get the sine wave synchronized to allow them to output in parallel. When I bought them I just assumed this would be a standard feature, silly me. These came without the info screens so I'm also finally getting them from powerjack after about a year, what a hassle its been dealing with powerjack. So any electrical wizards know if the circuits can be modified to synchronize? Also, I know these inverters are limited, any other suggestions on required modificatons to make them safer or more reliable would be appreciated.
Hello: I have two 10KW 48V input 240 split phase LF powerjack inverters. I'm looking for any information on how to get the sine wave synchronized to allow them to output in parallel. When I bought them I just assumed this would be a standard feature, silly me. These came without the info screens so I'm also finally getting them from powerjack after about a year, what a hassle its been dealing with powerjack. So any electrical wizards know if the circuits can be modified to synchronize? Also, I know these inverters are limited, any other suggestions on required modificatons to make them safer or more reliable would be appreciated.
Parallel inverters are a very difficult design proposition--and with the MCU-controlled SPWM inverters of today, the function has to be supported in software. (Which is not the case with a PJ inverter.) In short: there are no hardware modifications (short of replacing basically all of the internals of the inverter with custom designs) that will be able to result in the inverters being capable of parallel operation.
Yes, some might argue that there's a crystal on the control board, and "if the crystals were synchronized, they should run together"--well, that would possibly loosely be the case if the crystal was actually being used. But it's not being used: the MCUs are configured to run from their internal oscillators...which have a pretty lax tolerance.
FYI the info screens really don't give you much info either...just output voltage and current on a single AC leg. (Add frequency and power factor for good measure.) But as the info screens do not connect or communicate with the control board MCU, there is basically nothing to be gained from them.
Sid: thanks a lot... I'll get some wifi/bluetooth data logger then in place of the PJ screens, they wanted 80$ each.. Bummer on not being able to get a syncronization signal to share, I'm wiring them up now to separate panels to split the load but parallel would have been much better for the redundancy and wiring. When I bought them, I was making a comparison to the Aims 6K inverter and with the limited info available from PJ it was looking like the PJ 10k was just an Aimes knock off copy of the 6K model and would be the same. Silly Me. What I've seen elsewhere online is that the PJ L1 output is a pretty good sine wave but L2 will vary more with a less pure sine like wave and also the waveform degrades with voltage input. I hope to be up and running sometime this summer but its not on the highest priority list of things to get done first. Will see what happens when I get to installing the solar panels and wind turbine, If can upgrade to something else and just sell these. Life is a journey... thanks again
When I bought them, I was making a comparison to the Aims 6K inverter and with the limited info available from PJ it was looking like the PJ 10k was just an Aimes knock off copy of the 6K model and would be the same.
So you're actually pretty close...it turns out that ALL the Chinese LF inverters (including Aims, Sigineer, Sungold Power, Growatt, etc.) use basically the exact same core design, which was reportedly copied/"stolen" from Xantrex. Now, most of the Chinese inverter companies have made little adjustments/tweaks to the design--but the core modus operandi is the same. (I find this somewhat funny...no matter how big or how small the inverter, they all have exactly the same lopsided, imbalanced and weak MOSFET drive circuit. Talk about zero innovation!)
The crucial difference here between PJ and the other inverter manufacturers is that PJ tends to vastly overstate the continuous power capabilities of their inverter. For example, a PJ "8kw" generally will overheat the transformer and shut down at ~3kw continuous load.
What I've seen elsewhere online is that the PJ L1 output is a pretty good sine wave but L2 will vary more with a less pure sine like wave
They only put an AC filter cap on L1-N, but nothing on L2-N (which allows the unfiltered SPWM hash to come through, resulting in a "dirty sine"). You can add another 4.7uF 250vAC polyester capacitor from L2-N to clean that up. (Depending on the size of the inverter, sometimes they put 2-3 filter caps on the L1-N circuit on the output board...you can desolder one [or two] of those off the PCB, and put one on the L2-N circuit.
and also the waveform degrades with voltage input.
another "trick": PJ transformer winding specifications generally don't have enough headroom ("it stop the inverter blowing up" due to the weak FET drive)...so when the voltage falls, there's simply not enough transformer ratio to maintain the desired output voltage. As a result, the top of the sine wave starts to get clipped--it doesn't seem to hurt much of anything, but it's just not quite a sine wave.
Is it also true of the Aims 10k units that they have similar sinewave and continuous output limitations? I'll look into adding the CAP to the L2 output, I recall a video Sean had on this I watched some time ago.
Is it also true of the Aims 10k units that they have similar sinewave and continuous output limitations? I'll look into adding the CAP to the L2 output, I recall a video Sean had on this I watched some time ago.
I do not personally have an Aims unit...but that being said, I would not expect them to fall considerably short of their specced continuous output wattage like a PJ. However, I seem to have heard from someone utilizing Aims units, that they will eventually overheat and shut down at nameplate load...but I cannot corroborate this from personal experience, as I've never had an Aims inverter.
Aims inverters also cost considerably more than a PJ of the same nameplate--but once again, you kinda get what you pay for.
I would also be somewhat surprised if an Aims unit had no headroom in the transformer spec, so I don't think you'd have flat-topped sine waves. However, it is worth noting that you will get very high no-load losses, and output power with a high THD (total harmonic distortion) from an Aims inverter.
There is one other way you could parallel those inverters, sort of....
In the early days of powerjack, they built higher wattage units by paralleling transformers instead of making one huge transformer. Since you have two 10kw units of apparent same age, the transformers in each one should be the same. Although since we are talking about powerjack, the transformers could be radically different. You'll just have to look.
Anyway, you could take the transformer from the second unit and parallel it to the transformer of the first unit. Keep the rest of the second unit for spare parts. You now have one 20kw unit. You'll have to do some other stuff too, like beefing up the cooling fans, and changing the SW1 settings. The biggest challenge will probably be how to house the extra transformer since two transformers definitely won't fit in one case.
I'm not recommending this, as many things could go wrong. But it is a valid option if you are savvy enough and really want to do it. Since you said you could run an inverter on each of two load centers, that's probably a better way to go anyway. Gives you backup capability. Twice the no load loss though.
Food for thought
15 hours ago, dochubert said:There is one other way you could parallel those inverters, sort of....
In the early days of powerjack, they built higher wattage units by paralleling transformers instead of making one huge transformer. Since you have two 10kw units of apparent same age, the transformers in each one should be the same. Although since we are talking about powerjack, the transformers could be radically different. You'll just have to look.
Anyway, you could take the transformer from the second unit and parallel it to the transformer of the first unit. Keep the rest of the second unit for spare parts. You now have one 20kw unit. You'll have to do some other stuff too, like beefing up the cooling fans, and changing the SW1 settings. The biggest challenge will probably be how to house the extra transformer since two transformers definitely won't fit in one case.
I'm not recommending this, as many things could go wrong. But it is a valid option if you are savvy enough and really want to do it. Since you said you could run an inverter on each of two load centers, that's probably a better way to go anyway. Gives you backup capability. Twice the no load loss though.
Food for thought
Well, thats interesting.... I'm a retired mechanical engineer with a wide background with a lot of stuff including some electrical and structural work. I did a lot of DDC control work... My system is built with a lot of my old test equipment built in as permanent controls. So, Yes, i'm going to look at this...thanks...
Well, thats interesting.... I'm a retired mechanical engineer with a wide background with a lot of stuff including some electrical and structural work. I did a lot of DDC control work... My system is built with a lot of my old test equipment built in as permanent controls. So, Yes, i'm going to look at this...thanks...
I recommend independent temp sensors/fan controls on each transformer. Powerjack's fan controls are wonky at their best. You will want to monitor temps on each transformer anyway, as that will tell you if they are sharing the load evenly.
Below is a link to the temp control/sensor I use. It shows you the temp of your component plus the on and off setpoints of the fan connected to it. Simple, cheap and very reliable. I use one for each transformer plus one monitoring the output side heatsink of the mainboard. That one has its contacts paralleled to the original powerjack sensor switch to allow either the powerjack control board or your independent control to turn on the main fan(s).
So you have three controls monitoring mainboard temp and both transformers' temps, which lets you see how your equipment is doing at a glance. My inverter runs much cooler than powerjack would allow because of this setup. These controls are 12vdc, which if your inverter is 48v requires a 12 power supply. Here's another link, this one for the power supply I use for all my auxilliary controls. Good for 36-72v input and up to 10a so easily adequate. Also cheap and reliable. I've been using both of these items for more than 8 years with only one of the power supplies having died.
https://www.ebay.com/itm/152240514307?hash=item23723de503:g:0nUAAOSw6C5hCCkK
In my opinion (everybody's got one!), anybody running a powerjack should add independent temp sensors/controls to help your equipment run cooler and therefore, last longer. Depending on powerjack's control board to run fans enough is playing russian roulette. Eventually you get a bang!