After connecting the Victron autotransformer from a 240 inverter for solar I noticed a voltage difference of 117v on one leg and 123v on the other. what could be causing such a difference and is this a concern? Should it be returned and exchanged?
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Autotransformer output different
Did you ever figure this out? I just got a 32A Victron Autotransfomer and I’m running into the exact same problem. 240V single phase input (checked with multimeter), but getting 117V and 123V outputs, with or without load. I’m wondering if there is a batch of Victron autotransformers whose center tap isn’t exactly centered.
Hi @abauti
Indeed it is normal for our Autotransformer that the Centre tap isn’t exactly at the middle.
This is no problem at all, and everything will work fine.
It is not a regulated device, and all appliances are built to handle this amount of variation in the AC voltage without issues.
Indeed at my own house connected to the mains electricity grid, the voltage can fluctuate between 250 and 230 volts.
Thank you Guy! What is the output voltage tolerance range for the Autotransformer?
Hi @Eanthal,
We don’t publish a tolarance spec for the auto transformer - however the acceptable appliance range within the ANSI standard that covers the USA is 127V to 104V - appliances are designed to accept that as normal without issues.
https://voltage-disturbance.com/voltage-quality/voltage-tolerance-standard-ansi-c84-1/
If your loads are balanced, there is something wrong. Disconnect all loads and measure again. If there's still a difference you either have a defective unit or you have connected the center tap of the auto transformer back to the grid/shore power neutral and are seeing imbalance in the incoming AC input
This was the reading with no loads and no connection to grid. Thanks for the response. It's a bummer I have to return it.
I am having same issue, brand new unit with no load attached. I have a single phase 240 feeding in and with nothing connected on output I get 117 on one leg and 123 on the other. Emailed seller and he said this could be normal depending on the load but I have no load. From this post this seems like I should NOT be expecting this.
Did you ever find a solution? I just got a new 32A Victron Autotransfomer and I’m running into the exact same problem. 240V single phase input (checked with multimeter), but getting 117V and 123V outputs with or without load. I’m wondering if there is a batch of Victron autotransformers whose center tap isn’t exactly centered.
I also see a difference in voltages from each leg (L1 & L2) to neutral. It's off by about 4 volts, low on one side and high on the other side. According to the previous post by eanthal from Victron this is normal and should not cause a problem. I have found that this is true regarding to running loads off of the MPII inverter, and also when feeding power back into the grid from my IQ8 microinverters (PV) through the MPII. The real problem happens when with using an Autotransformer between a MultiPlus and my microinverters when the grid goes down. The microinverters try to come back up after the transfer switching is completed (which exceeds their anti-islanding window of 80 ms), but they go back down after hitting the point where the MP would be expected to switch from just inverting to both inverting (which is needed so the microinverters don't realize the grid is down) and also recharging the batteries, or performing frequency/watt control to throttle back the microinverter power production. I recently spoke to a Victron distributor representative about this problem. He told me that this arrangement wouldn't work for forming a microgrid. He implied that I wasted my money purchasing an autotransformer in my attempt. He told me that in order to do what I wanted to do, that I would have to buy another MPII and batteries to power it, then use both units together to create the 240 VAC with neutral (split-phase). But earlier in my conversation he told me that the single MP wouldn't be able to both invert (generate AC power) and charge the batteries. So now I am still confused. Most (if not all) Victron inverters are not "listed" for usage in the U.S., so your electrical inspector could not allow the system to pass inspection (mine told me so). It looks like I made several mistakes, so I just wanted to share my experiences so that I might spare someone else my pain.
I had the same problem and had to give up on the autotransformer solution and go with an AOI unit from a different manufacturer. The idea that is is acceptable is hogwash. In my case it was causing huge currents on the neutral because my neutral is bonded on both sides. Without that the neutral would have been 4V off ground which is also unacceptable.
The real problem stems from the fact that when the Quattro is in grid assist mode the two hot legs are bound to 120V each by the grid. This binding is passed through the Quattro and AT. The neutral then tries to move off center by the imbalance. I was getting a 10A current on the neutral with my load center input breaker off! Only switching off the breaker on the autotransformer would stop the current.
Signature solar refused to take this garbage back because Victron doesn’t consider it a problem. I’ve given up on Victron.
Anybody want to buy a Quattro for half price?
