3 Phase 75kVA Isolation Transformer for Superyacht NEVER SAY NEVER

Southern Transformers recently manufactured a custom 75kVA 3 phase isolation transformer solution for installation aboard the iconic, Jon Bannenberg-designed 36.9-metre superyacht NEVER SAY NEVER.

The transformer requirement was straightforward: 75kVA, 415V/415V, 3 phase isolation transformer.

The installation wasn’t.

A conventional 75kVA 3 phase dry-type isolation transformer would weigh approximately 400–500kg and could not be manoeuvred into the waterproof electrical switchroom in the lower section of the vessel without significant structural modifications.

Rather than modify the yacht to fit the transformer, we redesigned the transformer solution to fit the yacht.

The result was three 25kVA single-phase isolation transformers, each weighing approximately 130kg, designed to be manoeuvred individually into the switchroom and connected together on site to form a complete 75kVA 3 phase isolation transformer bank.

The Challenge

75kVA Wasn’t the Problem. Getting It Into the Boat Was.
Electrically, the requirement was well within our normal manufacturing range:

75kVA | 415V/415V | 3 Phase | Isolation Transformer

The difficulty was physical access.

The transformer was to be installed inside a waterproof electrical switchroom in the lower section of the superyacht.

A conventional 75kVA 3 phase isolation transformer would typically be constructed as a single unit weighing somewhere in the order of 400–500kg.

There simply wasn’t a practical way to manoeuvre a transformer of that size and weight through the vessel and into the switchroom.

Installing a conventional unit could therefore have required major modifications to the vessel – potentially including cutting an access opening through the fibreglass structure and subsequently repairing and refinishing it.

On a superyacht, that’s neither a simple nor inexpensive exercise.

So the actual engineering challenge became:

How do you get 75kVA of 3 phase isolation into a space that a conventional 75kVA transformer can’t physically reach?

The Solution

Three 25kVA Transformers. One 75kVA 3 Phase Transformer Bank.
Our solution was relatively simple: split the transformer, not the yacht.

Rather than manufacturing one conventional 75kVA 3 phase transformer, Southern Transformers manufactured three separate 25kVA single-phase dry-type isolation transformers.

Each transformer weighed approximately 130kg, making the individual units considerably easier to manoeuvre through the vessel and down into the electrical switchroom.

Once installed, the three transformers are connected together to operate as a single 75kVA 3 phase isolation transformer bank.

The completed system provides:

415V 3 phase, 3-wire Delta input
415V 3 phase, 4-wire Star output
240V line-to-neutral output
75kVA total capacity
Dyn11 vector group

The project schematic confirms the three individual 25kVA transformers forming the 75kVA Delta/Star bank.

Designed to Make Installation Straightforward

We didn’t want to simply supply three transformers and leave Rapid Electrical to work out how to turn them into the required 3 phase system.

The transformers were designed from the outset to operate together as a bank.

Each unit was supplied with clearly identified A, B and C phase terminals, along with suitably sized and labelled connection and linking leads.

Additional holes were provided in the copper terminals specifically to accommodate the linking leads without interfering with the primary customer connection points.

Southern Transformers also produced a dedicated connection diagram, schematic and single-line diagram showing Rapid Electrical exactly how the individual transformers were to be connected once installed aboard the vessel.

The physical connection drawing clearly identifies the three individual transformers and the required Delta primary and Star secondary interconnections.