Toroidal transformers

Our toroidal transformers, from 50 VA to 2 kVA

A toroidal transformer does the same job as any other transformer, stepping an AC voltage down or separating a circuit from the mains, but its magnetic core is shaped like a ring. We offer four standard models with a 230 V primary, each with its price shown for every rating, plus a custom version:

• 12 V toroidal transformer (230 V to 12 V), from 50 to 1,000 VA: halogen lamps, spotlights and pool lights running on 12 V AC.
• 24 V toroidal transformer (230 V to 24 V), from 50 to 2,000 VA: gate motors, irrigation solenoid valves and control circuits at 24 V AC.
• 2 × 12 V toroidal transformer (230 V to 2 × 12 V), from 50 to 630 VA: two 12 V secondaries, to be used separately or in series.
• 230 V / 230 V toroidal isolation transformer, from 50 to 1,000 VA: separates an appliance from the mains without changing the voltage.
• Custom toroidal transformer, from 50 to 2,000 VA: your own voltages, with the price calculated online.

Accessories for fixing the transformer: mounting dishes and a DIN rail mounting plate.

What is a toroidal transformer?

A toroidal transformer, also known as a toroid transformer or simply a toroid, has a magnetic core in the shape of a torus: a ring made by winding a strip of electrical steel on itself. The primary and secondary windings are spread all the way round the ring, instead of sitting on one limb of the core as in a transformer with E and I laminations. They remain two separate windings: there is no electrical connection between the 230 V mains and the output voltage.

The principle is the same as in any transformer: the alternating current flowing through the primary sets up a magnetic flux in the core, which induces the voltage in the secondary. A toroidal transformer changes the voltage, not the frequency, and always delivers alternating current.

Toroidal or conventional transformer: the differences

• More compact and lighter: for the same rating, a toroidal transformer takes up less space and weighs less than a conventional transformer.
• Quieter: the ring-shaped core hums less and radiates little magnetic field around it, which is why toroids are valued near sensitive equipment and in audio.
• A single bolt: it is fixed with one centre bolt and a mounting dish, instead of four screws.
• High inrush current: at switch-on, a toroid draws a high current. On the 230 V side, protect it with a time-lag fuse (T) or a type D circuit breaker: a fast-acting fuse would blow, and a type B breaker would trip.

A conventional transformer remains the right choice above 2 kVA, on three-phase supplies, or when a cover or an enclosure is needed: see our single-phase transformers, from 63 VA to 20 kVA, in IP00, IP23 or IP54.

Lighting, pools, gates: what a toroid is used for

• Low-voltage lighting: 12 V halogen spotlights and lamps, indoors and in the garden. See our lighting transformers.
• Pool lighting: 12 V AC pool lights, with the transformer installed outside zones 0, 1 and 2 of the pool, in the plant room. A pool installation must comply with IEC 60364-7-702 (NF C 15-100 in France). See the 230 V / 12 V swimming pool transformer and our garden and pool transformers.
• Automation: gates, irrigation solenoid valves, relays and contactors at 24 V AC. See our transformers for gates.
• Isolating an appliance: the 230 V / 230 V toroid separates an appliance from the mains without changing its voltage.
• Audio: the custom toroidal transformer is also available in an audio version.

How to choose and install a toroidal transformer

Voltage

Check the rating plate of the lamp or appliance: “12 V AC”, “12 V ~” or “AC/DC” means it will run on a 12 V toroid. LED strips and many LED spotlights need a regulated 12 V DC supply: use an LED power supply, not a transformer. Older instructions may quote 220 V, the former name of the 230 V mains in continental Europe.

Power rating

Add up the power of the lamps or equipment, multiply by 1.25 and choose the next rating up. A 300 W halogen pool light needs 375 VA, so a 400 VA toroid.

Installation

A toroid is an open transformer with no housing: install it in an enclosure or cabinet, in a dry place with air around it, as it gets warm in normal operation. It is designed for continuous duty at up to 40 °C ambient.

The centre bolt must never touch both the metal base and the metal lid of an enclosure: it would form a shorted turn, which destroys the transformer. At 12 or 24 V the current is high, so the cable size must be calculated from the power and the distance.

Made, wound and tested in Gailhan, France

Our toroidal transformers are wound and 100 % tested in our workshop in Gailhan, in the Gard, southern France, like our single-phase and three-phase transformers and our autotransformers; the same team handles orders, technical advice and customer service. Standard toroids come with a 2-year warranty and are dispatched from France within 24 to 48 h. Our extra-low-voltage toroids come under EN 61558-2-6, the standard for safety isolating transformers.

Professional buyers: a trade account shows prices excluding VAT, with an immediate 5 % discount.

Another voltage? The custom-built toroid

Need a voltage that is not available as standard, several secondaries, tappings, thermal protection or an audio version? The custom toroidal transformer is configured online, from 50 to 2,000 VA, with an instant price. For a special requirement, describe what you need and we will reply with a quote within 48 h. All our non-standard models are grouped under custom-built transformers.

By voltage: 230 V to 12 V transformers and 230 V to 24 V transformers.