Victron Energy Autotransformer — 120/240V Split-Phase (32A, 50A & 100A)

Flexible voltage conversion, split-phase balancing, and the key to running a 230V inverter/charger on US power. The Victron Energy Autotransformer is a single-phase toroidal transformer that steps voltage up or down (120V ↔ 240V), creates a balanced 120/240V split-phase supply from a single 240V source, and corrects load imbalance between the two legs of a split-phase system. It's a core building block for marine, RV, and off-grid AC systems — available in 32A, 50A, and 100A models, each with a built-in circuit breaker and a ground relay for use with Victron inverter/chargers.

Who the Autotransformer is built for

• Boats with a 230V (50Hz) inverter/charger — European-built vessels keeping their existing 230V Multi or Quattro can pair it with an autotransformer to output US 120/240V split-phase.
• Split-phase systems that need balancing — where uneven 120V loads on L1 and L2 are wasting inverter or generator capacity.
• Off-grid homes and shops — running a mix of 120V and 240V appliances from one supply.
• Installers — who want a single 240V inverter plus an autotransformer instead of two stacked 120V units.

What an autotransformer does

Step up / step down

Convert 120 VAC up to 240 VAC, or 240 VAC down to 120 VAC, to match your equipment to the supply you have — shore power, a generator, or an inverter.

Split-phase load balancing

This is the function that needs the most attention. On a 120/240V split-phase supply, 120V loads are almost never equal across the two legs — a hairdryer pulls 10A from one leg, a washing machine 20A from another. That imbalance means one leg hits its limit while the other still has spare capacity, so you can't use the full rating of the supply. Wired per Victron's diagram (leaving the supply neutral unused and letting the autotransformer create a new neutral), the autotransformer “absorbs” that imbalance through its windings — the difference current flows through the neutral, both 120V legs share the load evenly, and you get the full kVA of the supply.

Run a 230V (50Hz) inverter/charger on US split-phase

A 230V Victron Multi or Quattro can be configured for 60Hz and paired with an autotransformer to deliver standard US 120/240V split-phase power — the simplest way to keep a European-spec inverter/charger when refitting a boat for the US.

An alternative to stacking two inverters

Instead of stacking two 120V inverters for split-phase, you can use one 240V inverter plus an autotransformer. The advantage: with stacked inverters each leg is capped regardless of the other, while a 240V inverter + autotransformer lets one leg draw more when the other draws less (up to the autotransformer's unbalance rating). Where load is uneven, this often makes better use of inverter capacity.

Included ground relay & temperature protection

In inverter mode the neutral must be bonded to ground for a GFCI to work. The autotransformer includes a built-in ground relay, controlled by a 230/240V Multi or Quattro — the inverter/charger's own internal ground relay is disabled, and the autotransformer handles the neutral-ground bond. An over-temperature cutout (manual reset) protects the unit under fault conditions.

Choose your model

Size the autotransformer to the feed-through current your system needs across the two 120V legs. Not sure? Book a system consultation and our ABYC-certified Advisors will spec it with you.

Full technical specifications

• Input / output voltage: 120 / 240 VAC
• Frequency: 50 / 60 Hz
• Transformer type: toroidal (low noise, high efficiency)
• Input circuit breaker: included (two-pole; 32 / 50 / 100 A by model)
• Ground relay: built in, for use with a 230/240V Multi or Quattro
• Protection: over-temperature cutout, manual reset
• Enclosure: aluminium, IP21 (indoor)
• Terminals: screw terminals, up to 35 mm² / AWG 2
• Safety: EN 60076
• Warranty: 5-year limited Victron warranty

Recommended pairings

• Quattro 230V or MultiPlus-II 230V — configure for 60Hz and add the autotransformer for US 120/240V split-phase.
• Inverter/chargers — the full Victron Multi and Quattro range.
• Transfer switches & distribution — to complete the AC side of the system.

Why buy your Victron Autotransformer from Blue Marine

• Authorized Victron Energy Distributor — genuine product, fully supported warranty.
• ABYC-certified Advisors — real help configuring split-phase and 50Hz-to-60Hz conversions.
• Free US shipping over $49 from our Seattle warehouse.
• 60-day hassle-free returns.
• Local pickup available in Seattle, WA.
• Custom quotes & full system design — request a quote for a complete build.
• Dealer & installer program — apply here for trade pricing.