I am planning to purchase 2 Multiplus II (12v 3000W 120v units) and staking them in parallel. Then connecting an Autotransformer to step up to 240V.
Most of my loads will be 120v however I have a 240v motor for a compressor that I want to use occasionally.
I’m trying to figure out how I can set up my system for so I can run 120v and 240v loads.
The 240v motor for the compressor I’m planning to use is 3 phase and I know it will run using a Variable Frequency Drive. However I have to give the VFD 240v
I don’t really need 2 multiplus units for my normal 120 loads, but I would be close to the limit for the 240v motor with the VFD
Other option is 1 Quattro 5kw
I am planning to be connected to the grid occasionally, as this set up is on a sailboat.
Can anyone help me understand how best to configure? I have not purchased any equipment yet. I will have a large lithium bank.
For the compressor motor with the VFD. The VFD will convert single phase 240v to 3 phase 240v.
How big is this 3ph motor?
It’s pretty common practice around these parts to use a vfd to drive a 3ph motor from a single phase source but it is one of the least efficient ways to achieve 3ph power.
The auto transformer will limit your 240v current to 28a(32 peak) even if you go with the 100a model (they’re only rated 100a pass through, it’s the same transformer as the 32)
The multiplus is rated 3000kva not 3000w, so make sure you don’t undersize yourself. They’re only 2400w with .8 power factor, then factor in step up transformer and vfd losses and there isn’t much meat left on the bone
Dave,
Thank you for the prompt reply. There is another boat owner that did this without the Autotransformer using 1 multiplus unit running a 3ph 2.0HP (1.5KW) motor and a VFD. I haven’t been able to get a reply on how he configured his Multiplus, but I did email with a tech from united automation that makes the VFD. He said the input used had to be 240v single phase. Being that it calculated out to almost the maximum output of the mulitplus II 3kva unit, I felt that having 2 units or a 5kva Quattro would make more sense.
Ideally I would ideally like to run a 3HP (2.2kw) 3ph motor.
What about configuring the Autotransformer for 3 phase?
Or running a single phase 240v motor with a soft start?
Be mindful of the N>G bond control since the common method of transferring N>G relay control to the AT from the I/C is fine for the loads being served by the output of the AT. If the paralleled Multis are also supplying a load center, that load center will not have an upstream N>G at its source.
Charlie,
I don’t fully understand the ramifications of that. Would it work better with 1 5kva Quattro compared with 2 mulits in parallel? Or what about using 2 muliti’s connected as 240v then stepping down for load center that requires 120v
There are a few configuration options I see.
I’m going to assume the VFD takes 240V and produces the proper 3-phase for your motor.
I’m very concerned you are trying to do this with a 12V system.
The surge current on the batteries will be immense when starting that motor, even with the VFD.
Putting two Multiplus in parallel at 120V (same phase) and up converting to 240V with the AT is a bad idea, because your power will be limited by the neutral winding limitation of 28A (continuous). As mentioned above.
Recommendation Ignoring the 12V issue for the moment, simply stacking two 120V Multiplus-IIs (3 kVA) to make split phase 120/240V is the simplest approach, no autotransformer needed. That will give you 4800W continuous at 240V, great surge capability, and room for 120V loads.
I recommend avoiding autotransformers whenever possible (though I own two myself).
You could add an autotransformer after the Multiplus-es to balance the 120V loads better, but that is probably an unnecessary complication unless you think you need it.
Doing split phase 240 to feed the vfd is a better method imo than using a transformer
Though it is only 2400w 240v/ 4800w 120v
Rick Thanks for your reply!
Yes I was thinking 240v single phase to 240v 3 phas for the VFD
My battery bank will be 920ah LiFePo4 (I can add more, but don’t think it’s necessary). Another guy used 1 3Kva Multiplus with 600ah LiFePo4 battery bank to a VFD running a 1.5kw 2.0HP 3 phase motor, and it worked great for him. I would like to run a 3.0 2.2kw motor ideally, but I can run the smaller motor if I have to.
Where can I find the spec’s on the how to wire or configure 2 stacked Multiplus II’s to make split phase?
My 120v loads are not constant. Things like microwave, toaster, small washing machine, they draw about 750 watts each, vacuum, hair dryer, and some power tools can draw 1200watts. I don’t need to run those while the compressor is going. I will only use the compressor once in while and normally for only about 45 minute to an hour.
Also when I do run the compressor, I am planning to run my 12v DC generator that makes 100amps especially prior and during start up.
Regarding the VFD and 3 phase vs single phase. I can get a compressor motor for single phase and I found a soft starter made by another company that can do 6KW for 240v Any recommendations on that? I want to have as efficient as possible set up. Start up is the first hurdle the second would be overall power consumption.
Setting up split-phase or parallel single phase systems is done in VEConfigure or VictronConnect. The output neutrals of the multiplus-es need to be combined on a Neutral busbar. One unit is designated L1, and the other L2. That’s pretty much it.
Here’s a setup video:
Thank you.
Any suggestions on single phase vs 3 phase for a 240v electric motor off this split phase set up?
Not from me, but you can also try diysolarforum.com
It really depends on the application. If it’s a single speed application I would opt to just use a single phase motor and save all the extra messing around
A 3ph motor is generally more efficient and cost effective both in motor and wiring price (maybe not in this small of a motor) but any price and efficiency savings are far outweighed by trying to drive it from single phase power
I would opt to go with a 240v single phase motor and a pair of multiplus’s in split phase config (with an auto transformer to share 120v loads if you want to simply install this to feed an existing single phase panel and desire the whole 4800w@120v)
Dave thanks for that input. Based on how we have used power in the past. A single multiplus 3KVa would easily take care of our power demands. It was rare that we would ever use that much AC power at one time. With that, I don’t think we would really benefit from the Autotransformer. I’s not that expensive, so if it fits in the installation I will consider it.
I’m going to reach out to the tech regarding the soft start for a single phase 240v motor to get the specs on start up load with the soft start
Oh yes for sure. Definitely not something that needs to be implemented at this time. just something to keep in mind should you ever require more 120v power in the future, it’d be an easy way to double the available 120v power
I really appreciate all the feed back!!!
I just re-read this. Is that right that I would only get 2400w at 240v? In the thread above Rick says 4800w for 240v.
Can either of you verify that?
you’ve got two 2400W continuous inverters
watts add (2400W+ 2400W = 4800W continuous)
and if wired for split-phase, voltages add (120V + 120V = 240V)
but current stays the same
It’s a lot easier to look at AC amps.
In split phase, 20A @ 120V + 20A @ 120V = 20A at 240V
Power is power, you’ve got 4800W at your disposal with split phase.
You can have up to 2400W @ 120V on one inverter, and up to another 2400W @ 120 V on the second inverter.
You can have 10A @ 240V for your motor, leaving up to 10A for L1 120V loads and up to 10A for L2 120V loads.
With an autotransformer balancer, you can maximize the available wattage of the two multipluses, but this isn’t necessary unless you have very unbalanced loads.This would let you put more than the allowable wattage on L1 or L2 by borrowing power from the other inverter through the AT coil.
Absolutely my bad, too many things going on in my head at the same time!
Rick is correct, with the 2 multiplus 3kva’s you’d have 2x 20a/2400w 120v and/or 1x 20a/4800w 240v available.
If your 120v loads are minimal while using the motor this would work perfectly. I’d expect that motor to draw no more than 15a running, which leaves you at least 2x 5a/600w 120v while using the motor.
If you can aquire a soft start for this motor that will keep the multiplus happy during startup I think you’re on the right track instead of trying to run a vfd and incur those losses in phase conversion which are likely going to push the 3kva multiplus to its limits