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Victron Autotransformer Balancing Efficiency

ricardocello

Watching and Learning
Joined
Apr 4, 2023
Messages
2,174
Location
Virginia, USA
I've got two stacked Victron Quatto 5k/48s feeding a Victron 100A autotransformer to balance loads between the two Quattros.
Zero-load power consumption including all DC devices with PV power disconnected is 101 W ("idle power", but I hate that name).
@740GLE @sunshine_eggo

I've got a ~1200W heater load for testing efficiency.
I have a switchable relay to take the load output neutral from either the Autotransformer or the combined neutral of the Quattros.
When the autotransformer neutral is not used, the L1 and L2 are still connected, incurring a small inefficiency.

This test is running on inverter power only, no grid.
DC Power is measured by Victron SmartShunt.
DC Power consumers include the two Quattros, a SmartSolar 250/100, a SmartSolar 250/70, a SmartShunt, a Cerbo GX, and an active relay.
PV power is not connected.

When balancing the load with the autotransformer:
AC Power: L1 Quattro 591 W, L2 Quattro 570 W
DC Power: 1265 W
Efficiency: 91.8%

When not balancing the load with the autotransformer (using Quattros only):
AC Power: L1 Quattro 1207 W, L2 Quattro 0 W
DC Power: 1355 W
Efficiency: 89.1%

I wasn't expecting that.
For this test, balancing both Quattros with the Autotransformer is more efficient.
The AC power readings from the Quattro aren't always that accurate, but they stayed within a few watts during the test.

Need bigger loads to test with.

Original thread:
 
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You ran this test with a simple resistive load, try it with a decent inductive load. I wonder how they’d compare.

With victron being one of the few who list VA ratings I’d love to see their analogs report VA consumption. Or least have the ability to toggle PF in victron connect or maybe in a Cerbo or something.
 
Same setup as first post.
Second test, doubled the resistive load with a second heater
Sorry, no inductive 120V loads handy right now, I'll have to give that some thought.

When balancing the loads with the autotransformer:
AC Power: L1 Quattro 1268 W, L2 Quattro 1260 W
DC Power: 2780 W
Efficiency: 90.9%

When not balancing the loads with the autotransformer (using Quattros only):
AC Power: L1 Quattro 2676 W, L2 Quattro 3 W
DC Power: 2969 W
Efficiency: 90.2%

Note that the neutral current imbalance on this test is about 21.6A when the autotransformer is active.
Loads are only present on L1.
 
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When the autotransformer neutral is not used, the L1 and L2 are still connected, incurring a small inefficiency.
@ricardocello is there a specific use case where you use combined neutral vs Autotransformer neutral? What happens when you pass grid through (charging and powering loads)?
 
An auto-transformer isn't going to help balance the loads of an already split-phase system. It's not going to help much with surges either.
You will need an isolation transformer to do that.
You can test this by (temporarily) disconnecting the input neutral from the transformer. It will balance everything, but isn't safe, because you lose the N/G bond. And before you say it, no, you can't create a second bond on the load side. Because that would put current on the ground. This is why it would have to be an isolation transformer.
 
@ricardocello is there a specific use case where you use combined neutral vs Autotransformer neutral? What happens when you pass grid through (charging and powering loads)?
The short answer is that when the Autotransformer neutral is combined with the grid neutral, it effectively puts the utility transformer in parallel.
In my house, I've got 2x 200A service. Having the autotransformer neutral connected to the grid neutral meant that it was balancing the other side of the house (no critical loads there), which was weird.
 
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Since this is my thread, this is probably a good place to document my quattro/autotransformer/switched neutral setup.

Quattros and Autotransformer.png
 
Since my setup is built into a rolling 19" rack, I built in a SquareD HOM Load Center, and gave myself all kinds of outlets (most of which I never use).

Output Panel.png
 
You ran this test with a simple resistive load, try it with a decent inductive load. I wonder how they’d compare.

With victron being one of the few who list disclose that their ratings are actually VA ratings (as all inverters are rated in VA) I’d love to see their analogs report VA consumption. Or least have the ability to toggle PF in victron connect or maybe in a Cerbo or something.

Fixed. ALL inverters are rated in VA.

😁
 
Tim has his “not 180 degrees two-phase split-phase” thing, you’ve got your “inverter VA/Watts rating” thing. 😜
The consistency of your messaging may someday reap benefits. Hopefully.

I'll still argue with him that it's different when it's two 120V inverters in split phase... and then he'll point at your config... :P
 
Yet victron doesn’t spit out VA in any analog value they report via victron connect or a Cerbo.

If a killawatt plug in meter can spit out VA and PF, just kinda wish victron could as well.
I just looked through all of the custom VRM widget options for the quattros and system.
You are correct, they do not (and cannot) measure VA and PF.

I’ve got two EM530 energy meters that can do that, but they are $$$ and in use as grid meters.

I’ve got a Shelly Pro EM-50 ($81) that can do “four-quadrant” VA and PF measurements on two channels with 50A CTs.
Maybe I’ll put it on the inverter outputs and take measurements on L1 and L2.
 
I just looked through all of the custom VRM widget options for the quattros and system.
You are correct, they do not (and cannot) measure VA and PF.

I’ve got two EM530 energy meters that can do that, but they are $$$ and in use as grid meters.

I’ve got a Shelly Pro EM-50 ($81) that can do “four-quadrant” VA and PF measurements on two channels with 50A CTs.
Maybe I’ll put it on the inverter outputs and take measurements on L1 and L2.
“Do not” and “cannot” are two different things.

It’s just maths and should be well within an easy implementation via software, there are already PT and CT in the multiplus. Maybe they need higher grade measuring devices.

A cheap killawatt can do it, imo everything should be able to do it.

It is one reason why I haven’t shelled out cash for a whole home energy monitor.
 
“Do not” and “cannot” are two different things.

It’s just maths and should be well within an easy implementation via software, there are already PT and CT in the multiplus. Maybe they need higher grade measuring devices.

A cheap killawatt can do it, imo everything should be able to do it.

It is one reason why I haven’t shelled out cash for a whole home energy monitor.
I probably jumped the gun on "cannot".

I know they can determine power direction on the AC inputs because they are designed to measure and push power back.
I'm not sure if they can do it on the AC outputs, though.
Maybe they can since AC-coupled pv power can be on the output, not sure.

Totally agree that if they can measure it, they should provide it.

Offtopic: Kind of like the internal temperature sensor on the SmartSolar MPPTs (which is now readable because someone wrote a driver).
 
Doesn’t your inverter let you see output voltage and current? Multiply them to get VA.
Are you implying that the Watts they calculate are not equal to just Volts times Current anyway?
And that VA is just really VA and it is different than the Watts value?
Meaning we can compute the power factor ourselves?
And that the signs will give us the correct quadrant?

If so, I feel like a complete idiot!!

:fp2

Power Factor = W / VA = cos ϕ
And if amps are negative, we know it is exporting power.

Looking for information to determine these quantities (ideally), like my EM530s.
Though I can live with just knowing quadrants I and II.

Screen Shot 2025-01-13 at 6.22.14 PM.png
 
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@DougfromdaUP Thanks for pointing out the painfully obvious point (which I totally missed) that Victron gives us Watts, Current (signed), and Voltage. And that VA is of course literally just Volts*Amps, and that Watts are true power.

I've updated my script to monitor the Quattro Input/Output Watts to include VA and Power Factor.

Sure enough, they are different. In this case, I am intentionally pushing back 7000W back through the AC input (ignore the output).

Code:
Quattros: [Input -4530 W  -5366 VA  0.84 PF] [Output -70 W   -121 VA  0.58 PF] [ESS Setpoint -7048 W] [Ripple 0.00 0.00 V]
Quattros: [Input -5360 W  -6139 VA  0.87 PF] [Output -80 W   -109 VA  0.73 PF] [ESS Setpoint -7061 W] [Ripple 0.00 0.00 V]
Quattros: [Input -6140 W  -6839 VA  0.90 PF] [Output -100 W   -12 VA  8.33 PF] [ESS Setpoint -7084 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7000 W  -7355 VA  0.95 PF] [Output -100 W   -98 VA  1.02 PF] [ESS Setpoint -7093 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7010 W  -7355 VA  0.95 PF] [Output -90 W   -73 VA  1.23 PF] [ESS Setpoint -7098 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7050 W  -7305 VA  0.97 PF] [Output -90 W   -61 VA  1.48 PF] [ESS Setpoint -7096 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7020 W  -7355 VA  0.95 PF] [Output -90 W   -98 VA  0.92 PF] [ESS Setpoint -7094 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7030 W  -7293 VA  0.96 PF] [Output -90 W   -158 VA  0.57 PF] [ESS Setpoint -7095 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7030 W  -7379 VA  0.95 PF] [Output -90 W   -122 VA  0.74 PF] [ESS Setpoint -7094 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7030 W  -7367 VA  0.95 PF] [Output -90 W   -98 VA  0.92 PF] [ESS Setpoint -7093 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7080 W  -7355 VA  0.96 PF] [Output -110 W   -158 VA  0.70 PF] [ESS Setpoint -7091 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7030 W  -7367 VA  0.95 PF] [Output -90 W   -98 VA  0.92 PF] [ESS Setpoint -7101 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7070 W  -7490 VA  0.94 PF] [Output -110 W   -73 VA  1.51 PF] [ESS Setpoint -7099 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7080 W  -7355 VA  0.96 PF] [Output -100 W   -73 VA  1.37 PF] [ESS Setpoint -7104 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7080 W  -7355 VA  0.96 PF] [Output -110 W   -73 VA  1.51 PF] [ESS Setpoint -7102 W] [Ripple 0.00 0.00 V]
Quattros: [Input -6960 W  -7317 VA  0.95 PF] [Output -90 W   -98 VA  0.92 PF] [ESS Setpoint -7105 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7010 W  -7478 VA  0.94 PF] [Output -100 W   -159 VA  0.63 PF] [ESS Setpoint -7099 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7030 W  -7317 VA  0.96 PF] [Output -90 W   -122 VA  0.74 PF] [ESS Setpoint -7097 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7080 W  -7379 VA  0.96 PF] [Output -100 W   -97 VA  1.03 PF] [ESS Setpoint -7091 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7050 W  -7391 VA  0.95 PF] [Output -90 W   -135 VA  0.67 PF] [ESS Setpoint -7099 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7130 W  -7502 VA  0.95 PF] [Output -110 W   -135 VA  0.81 PF] [ESS Setpoint -7097 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7070 W  -7379 VA  0.96 PF] [Output -100 W   -159 VA  0.63 PF] [ESS Setpoint -7104 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7040 W  -7317 VA  0.96 PF] [Output -90 W   -36 VA  2.50 PF] [ESS Setpoint -7100 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7050 W  -7379 VA  0.96 PF] [Output -100 W   -97 VA  1.03 PF] [ESS Setpoint -7099 W] [Ripple 0.00 0.00 V]
Quattros: [Input -7060 W  -7379 VA  0.96 PF] [Output -90 W   -122 VA  0.74 PF] [ESS Setpoint -7097 W] [Ripple 0.00 0.00 V]
 

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