Low Voltage Transformers - Toroidal (Magnetic)
Low voltage lamps are not wired directly to the mains. A transformer is used to reduce 220-240v mains to a lower voltage (usually 12 volts). The transformers listed here are for internal use, see exterior section for outside transformers. If you want to understand more about how transformers work and the differences between transformer types see the bottom of this page.
Transformer that reduces mains voltage to less than 25 volts are called low-voltage transformers. They are often used to reduce mains voltage in the home from 220 volts to 12 volts. A wide variety of light fixtures use these transformers to power smaller lamps. Both electronic and magnetic transformers are in common use, each having its own advantages.
Magnetic Low Voltage Transformers
Understanding the magnetic low voltage transformer
Magnetic transformers use two coils of wire; primary (incoming) and secondary (outgoing). The primary coil carries the input from the mains or high voltage and creates a magnetic flow which induces a current in the secondary coil of wire. Because the primary wound coil has more windings or wire than the second coil, the secondary coil has a lower voltage. There are two basic designs of magnetic transformers; toroidal (shaped like a ring doughnut) or stacked (square or rectangular). Stack laminated transformers have a core of laminations punched from metal sheets. The metal is an alloy of iron and nickel and the percentage of nickel is adjusted to provide an energy loss when the primary winding or coil is energised. A toroidal transformer has a core constructed from a strip of a similar nickel iron alloy wound in a helix to shape a circular core.
Advantages of magnetic low voltage transformer
Laminated transformers are long-lived, lasting typically 15 to 20 years. Toroidal transformers last longer and are extremely quiet when compared to either the stack laminated magnetic transformer or the electronic transformer. Both types of magnetic transformers are rated at higher operating temperatures than electronic transformers.
Disadvantages of magnetic low voltage transformer
Size and weight of magnetic transformers can present problems when designing smaller light fixtures or when used in surface mounted lighting. Dimming of magnetic transformers is possible but buzzing is often caused at the dimmer module or transformer or in both locations. Toroidal transformers can have large inrush current when switched on. These transformers may have to be run from Type C miniature circuit breaker.