What Does an Isolation Transformer Do?
An isolation transformer transfers AC power from a shore supply to an onboard electrical system with no conductive path between input and output. The shore power feeds the primary winding; the vessel connects to the secondary. Energy converts to a magnetic field and back to electricity on the secondary side, breaking all electrical continuity between the shore ground and the boat. This eliminates the risk of electric shock through the water, prevents galvanic corrosion on underwater metal fittings, and suppresses electrical noise in sensitive onboard electronics.
Galvanic Corrosion: Why Isolation Is Required in Marine Installations
Galvanic corrosion occurs when two dissimilar metals in electrical contact are simultaneously exposed to a conductive fluid, seawater and, to a lesser extent, freshwater. When a vessel connects to shore power without an isolation transformer, the shore ground wire connects to the boat's metal hull, keel, propeller shaft, and underwater fittings, creating a galvanic circuit with other vessels connected to the same marina supply. The more active metal in the circuit corrodes preferentially. An isolation transformer completely eliminates this path. It replaces the need for a galvanic isolator and removes the requirement for polarity alarms.
Victron Energy Isolation Transformer Range
Buy Victron Energy isolation transformers for professional marine installations, off-grid cabins on shore power, and any system requiring galvanic separation between an AC input and a sensitive load. All models use toroidal wound transformer technology for quiet operation, compact form factor, and high continuous efficiency. Soft-start circuitry manages inrush current on power-up, preventing nuisance trips on marina shore power breakers.
Choose the Right Isolation Transformer
- Isolation Transformer 2000W (115/230V): Best for small boats, cabins, and sensitive electronic equipment. Supports 115V or 230V operation with manual voltage selection.
- Isolation Transformer 3600W (115/230V): Ideal for mid-size marine systems, RV shore power connections, and off-grid cabins. Offers 115V or 230V operation with manual switching.
- Isolation Transformer 3600W Auto (115/230V): Designed for mixed-voltage marinas and vessels that frequently move between different shore power standards. Automatically switches between 115V and 230V input.
- Isolation Transformer 7000W (230V): Built for large vessels and commercial marine systems with higher power demands. Provides 7,000W capacity for 230V installations with manual operation.
Manual vs. Auto-Switching Models
Choose a manual isolation transformer when your shore power voltage is fixed and consistent, a dedicated 115V or 230V supply in a permanent marina berth or cabin installation. Select the 3600W Auto 115/230V model when the vessel moves between marinas supplying different voltages, or when connecting to both North American 120V and European 230V shore power without rewiring. The auto-switching model detects input voltage and configures output automatically.
Beyond Marine: Other Applications
Install an isolation transformer in off-grid cabin systems to suppress electrical noise between a generator or grid input and sensitive electronics, solar inverters, audio equipment, medical devices, and laboratory instruments. Isolation transformers also resolve ground loop interference in audio and video systems, and provide a safety barrier in any installation where the AC input ground must not connect to the load-side chassis.
Key Attributes to Compare
- Rated power (2,000W, 3,600W, 7,000W), size to the total continuous AC load on the secondary side
- Voltage configuration (115V, 230V, auto 115/230V), match to shore supply and onboard system voltage
- Auto-switching, required for vessels operating across mixed-voltage marinas or international waters
- Toroidal construction, lower noise, higher efficiency, and lighter weight vs. conventional transformer cores
- Soft-start circuitry prevents shore breaker trips during power-up inrush
FAQs
What Is The Difference Between An Isolation Transformer And A Galvanic Isolator?
A galvanic isolator uses diodes to block low-voltage DC galvanic currents on the shore ground wire while still allowing the AC safety ground to pass. An isolation transformer eliminates all electrical continuity between shore power and the vessel, including the ground conductor, by magnetically transferring energy between windings with no conductive path. An isolation transformer provides complete galvanic isolation and replaces the need for a separate galvanic isolator.
Is An Isolation Transformer Necessary If My Boat Is Already Fitted With A Galvanic Isolator?
A galvanic isolator blocks low-level DC corrosion currents but does not eliminate all electrical connection to shore ground. An isolation transformer provides a higher level of protection by completely removing the conductive path between shore and vessel. For professional marine installations, or any vessel with aluminium, bronze, or mixed-metal underwater fittings in saltwater, an isolation transformer is the more reliable long-term solution.
What Size Isolation Transformer Do I Need For My Boat?
Add the rated wattage of all AC loads you plan to run simultaneously, air conditioning, battery charger, inverter, galley appliances, and electronics. Select the next model up from that total to allow headroom. A vessel running a 1,500W battery charger and 300W in general AC loads requires a minimum 2,000W unit. Systems with air conditioning or large inverter chargers typically require 3,600W or higher.
What Does Auto-Switching Mean On The 3600w Auto Model?
The 3600W Auto 115/230V model detects the incoming shore power voltage and automatically configures its output to match, switching between 115V and 230V without manual reconfiguration. This is essential for vessels that move between North American marinas supplying 120V and European or international marinas supplying 230V, eliminating the need to rewire or adjust a voltage selector switch between berths.
What Is Toroidal Wound Technology And Why Does It Matter?
A toroidal transformer winds its copper coils around a doughnut-shaped iron core rather than the rectangular E-I core used in conventional transformers. This geometry reduces magnetic flux leakage, lowers audible hum under load, improves energy efficiency, and results in a lighter, more compact unit at equivalent power ratings. All Victron isolation transformers use toroidal construction.
Will An Isolation Transformer Prevent Electric Shock Drowning?
Electric shock drowning occurs when AC voltage leaks into the water around a vessel connected to shore power, creating a voltage gradient that can paralyze or kill swimmers. An isolation transformer eliminates the shore ground connection to the vessel, removing the path through which this leakage current flows. Marine electrical safety standards in several jurisdictions recommend or require isolation transformers specifically to prevent electric shock drowning in marina environments.
Can I Use An Isolation Transformer For Non-Marine Applications?
Yes. Isolation transformers are used in off-grid cabins and RV installations to suppress electrical noise between a generator input and sensitive electronics. They are also used to resolve ground loop interference in audio and video systems, provide a safety barrier in laboratory and medical equipment installations, and isolate AC power circuits in any system where shared grounding between input and output would cause interference or safety issues.
Does The Victron Isolation Transformer Work With An Inverter Charger?
Yes. The isolation transformer installs between the shore power input and the rest of the onboard AC system, including the inverter charger. Shore power connects to the transformer primary; the secondary feeds the inverter charger AC input and other onboard AC loads. This configuration provides galvanic isolation for the entire vessel electrical system while allowing the inverter charger to charge batteries and manage AC loads as normal.
