Victron Energy Autotransformer for 120/240V Power, 32A Output, Converts 120V or 230V to 120/240V

Victron Autotransformer 120/240V-32A for Split-Phase Step-Up and Load Balancing

The Victron Autotransformer 120/240V-32A uses one toroidal winding with a center tap in place of separate primary and secondary coils. That single winding can step a 120V source up to 240V, create a neutral for a 240V source that has none, or hold the two legs of a 120/240V supply in balance when the loads on each side don't match. Because input and output share the same winding, it does not provide galvanic isolation the way an isolation transformer does. Victron has superseded the 32A unit with the Autotransformer 120/240V-50A, and this page documents the original model for systems that already have one in service.

Stepping 120V Up to 240V

Feed 120V into the autotransformer and it doubles the incoming voltage across its outer terminals, which lets a 120V shore cord, a 120V generator, or a single 120V inverter run 240V appliances. On this connection, capacity is set by the neutral rating rather than the 32A feed-through figure. Victron rates the 32A model for 32A of neutral current for 30 minutes, equal to 3,800 VA, and 28A continuously at 40°C (104°F).

Creating a Split-Phase Neutral From a Single 240V Inverter

With a 240V inverter on its input, the center tap becomes the neutral for a 120/240V split-phase output, so one inverter can serve both 120V and 240V circuits; a 230V inverter produces a 115/230V split the same way. Victron's sizing example pairs a 240V 5kVA inverter with this 32A unit for up to 21A of balanced load on each 120V leg and as much as 35A of difference between the legs, so one leg can carry 38.5A while the other carries 3.5A. Two stacked 120V 3kVA inverters top out at 25A per leg, which is why Victron favors the single-inverter arrangement wherever uneven loading is expected.

Balancing Uneven Loads on a 120/240V Supply

A 30A 120/240V shore or generator supply has a theoretical ceiling of 7.2 kVA (30A x 240V). With a 20A imbalance between the legs, the heavier leg reaches its limit first and usable capacity drops to about 4.8 kVA, or 67% of that ceiling. The autotransformer creates a new neutral and absorbs the imbalance, letting the supply deliver close to its full rating.

Ground Relay and Inverter Integration

A ground relay inside the enclosure bonds neutral to ground while the system runs on inverter power and opens when an outside source with its own bond takes over. With a 230/240V Victron MultiPlus, MultiPlus-II, or Quattro, the inverter/charger switches this relay from its ground relay terminals using a 24V signal, the same on 12V, 24V, and 48V models. The inverter/charger's own internal ground relay is deactivated per Victron's manual (the SW1 slide switch on a MultiPlus or Quattro, a settings change on a MultiPlus-II) so the bond is made in one place.

Thermal Protection and Mounting

A fan switches on and a red LED lights when the transformer runs warm. If it overheats, the input breaker trips and disconnects the unit from the supply; reset is manual, by cycling the breaker after shedding some 120V load. The aluminum enclosure is rated IP21 for dry indoor locations and mounts in any orientation, with vertical giving the best cooling and terminal access. Leave at least 10 cm (4 in) of clear space around it with the vents unobstructed. Screw terminals accept conductors up to 35 mm² (2 AWG), and wire size follows the protection provided by the circuit breakers.

Replacement Model: Victron Autotransformer 120/240V-50A

Victron's 50A model replaces the 32A unit. It keeps the same 214 x 110 mm width and depth, the same 35 mm² terminals, and the same 12.5 kg weight, while raising feed-through to 50A and the neutral rating to 55A for 30 minutes and 45A continuous at 40°C. The housing is 35 mm taller (460 mm versus 425 mm), so confirm the mounting space before swapping one for the other. Our team is happy to help match a replacement to an existing system; reach us through the contact form.

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