Victron 100A Autotransformer: Precision Voltage Conversion and Split-Phase Balancing for Critical Power Systems

Engineered for Reliable Step-Up, Step-Down, and Load Balancing in 120/240V Applications

The Victron 100A Autotransformer is a robust, toroidal transformer designed to solve the challenges of split-phase power distribution. In systems where 120V and 240V loads coexist, unbalanced currents can severely limit usable capacity. This unit actively balances the load across both legs, enabling you to draw the full rated power from your supply—whether it’s a generator, grid connection, or inverter setup.

By creating a new neutral point, the autotransformer absorbs current differences between the two 120V legs. This means a 30A 120/240V supply can deliver its full 7.2kVA potential, rather than being restricted to as little as 4.8kVA due to imbalance. For installers and system designers, this translates to fewer overload trips, better utilisation of existing infrastructure, and a more stable power environment for sensitive equipment.

How It Solves Real-World Power Problems

In typical mobile, marine, or off-grid installations, 120V appliances like hairdryers, washing machines, or air conditioners can draw heavily from one leg while the other remains lightly loaded. Without balancing, the supply breaker may trip prematurely, even though total power draw is well below the theoretical maximum. The Victron Autotransformer eliminates this bottleneck, allowing dynamic redistribution of current so that both legs operate efficiently.

This capability is particularly valuable when using a single 240V inverter instead of stacking two 120V units. A stacked pair of 120V 3kVA inverters limits each leg to 25A regardless of load distribution. In contrast, a 240V 5kVA inverter paired with this autotransformer can supply up to 38.5A on one leg if the other draws only 3.5A—offering greater flexibility and often reducing equipment costs.

Built-In Safety and Protection Features

Safety is integral to the design. An integrated ground relay ensures the neutral is properly bonded when operating in inverter mode, which is essential for the correct function of Ground Fault Circuit Interrupters (GFCIs). The relay is controlled directly by a compatible Victron Multi or Quattro inverter/charger, simplifying installation and compliance.

Thermal protection guards against overheating: if internal temperatures rise beyond safe limits, the unit disconnects automatically. Reset is manual, prompting a check of ventilation and load conditions before resuming operation. The 100A two-pole circuit breaker provides additional overcurrent protection on the input side.

Key Features

• Toroidal transformer design for high efficiency and low noise
• Continuous neutral current rating of 28A at 40°C, with 32A for 30 minutes
• Integrated ground relay for seamless inverter neutral bonding
• Manual-reset thermal protection prevents damage from overload
• Robust aluminium enclosure with IP21 protection rating
• Screw terminals accept up to 35mm² (AWG 2) cable for secure, low-resistance connections
• Compact footprint: 425 x 214 x 110mm, weight 13.5kg

Applications Across Mobile, Marine, and Off-Grid

This autotransformer is an essential component for any split-phase system where load balance cannot be guaranteed. Typical use cases include:

• RV and caravan power systems with a mix of 120V and 240V appliances
• Marine electrical panels requiring stable split-phase supply from a single inverter
• Off-grid cabins or tiny homes using generators or inverters as primary power sources
• Backup power setups where generator capacity must be fully utilised
• Industrial or commercial mobile power carts

Whether you’re upgrading an existing Victron installation or designing a new system, the 100A Autotransformer provides the balancing capability needed to maximise available power and protect connected equipment.

Installation-Ready Design

The unit ships with clear wiring diagrams and features accessible screw terminals, dual cable glands for secure cable entry, and mounting feet for fixed installation. LED indicators on the front panel provide at-a-glance status for power, ground relay engagement, and temperature warnings, aiding commissioning and troubleshooting.

For systems requiring step-up conversion from 120V to 240V, the autotransformer can be configured accordingly, adding versatility to its split-phase balancing core function.

Maximise Your Power System’s Potential

Equip your installation with the Victron 100A Autotransformer to eliminate load imbalance limitations and ensure reliable, full-capacity operation. Order today to build a more resilient and efficient power system.