What does Victron Energy Autotransformer do?

The Victron Energy autotransformer is mainly used for step up - step down and split phase output balancing. the step up -step down converter functionality is a straightforward process allowing 220/240 devices to work with a 110/120 input from the primary voltage or 110v devices

The step up - step down feature is similar to any other voltage converter that takes the high or low primary voltage and transforms it into the required secondary voltage. For instance, if you are using a 220/240V generator for devices that mainly use 110/120 volts, the Autotransformer will adjust the voltage so all appliances can run smoothly.

The main difference between the Autotransformer and other winding transformers is the split-phase output balancing. Let's look at a typical converter of 120/240V and 30A. in theory. This converter should produce a power of 120 x 30 + 120 x 30 or 30 x 240, equal to 7.2 kVA. However, in reality, they work with much lower total power.

This inefficiency is the current unbalance between the two 120V legs. Once each leg is connected to a load, the voltage and current flow toward that device separately. For example, the leg connected to a hair dryer will draw 15 amps, and the leg connected to a coffee maker will start drawing 30 amps of current. This unbalanced distribution of power will overload one leg, whereas the other leg still has unused current. Therefore, this transformer is using 30 x 120 + 10 x 120 = 4.8 kVA which is only 67% of the potential power.

The split-phase in the Autotransformer will fix this issue by leaving the neutral of the split-phase supply voltage unused. By connecting the Autotransformer as a new neutral like the figure below, any unbalance load will be reabsorbed and transferred into the windings of the Autotransformer. The 20 amp load will result in one leg supplying 40A and the other leg 20A. The 20A difference will flow through the neutral and the windings of the Autotransformer.

Ground relay for use with Multi or Quattro Inverter/Chargers included

The neutral output of the inverter/charger must be connected to the ground to guarantee the proper functioning of a GFCI. For this purpose, a grounding relay is built in the Autotransformer's enclosure. The relay is controlled by the 230/240V Multi or Quattro

(The internal grounding relay in the 230/240V Multi or Quattro must be disabled)

Other Features:

Temperature protection: Automatic shut down in case of overheating

An alternative to stacked inverters: The alternative to stacking two 120V inverters to provide a 120/240V split phase supply is a 240V inverter with an additional Autotransformer.