A low voltage transformer converts the standard main power supply voltage into a lower voltage, usually 12 to 15 volts. It is used in a variety of applications, including low-voltage landscape lighting systems.

A low-voltage transformer can be either magnetic or electronic. The magnetic type is more energy efficient but runs at a lower rate of efficiency, approximately 80 to 85 percent.

Magnetic core

The magnetic core of a low voltage transformer provides a controlled path for the magnetic flux generated by the primary winding. It can be either a solid bar of steel or a construction of many thin laminated steel sheets or layers.

The primary and secondary coils are positioned around the core. There are two main types of cores used in transformers: “core type” and “shell type.”

A core type construction has the windings wound concentrically around the central leg or limb of the transformer’s magnetic circuit. This has the advantage of overcoming the leakage flux that can be caused by the windings being arranged in different directions.

In addition to losses in the core itself, such as eddy currents and hysteresis, the skin effect in the winding conductors also increases power loss. This is why a transformer must be designed with a good cross-sectional area for maximum energy efficiency.

Secondary winding

The secondary winding of a low voltage transformer converts alternating magnetic fields into electrical power. This occurs when the primary winding is energized by an input voltage supply.

The current induced into the secondary winding of a transformer depends on its turns ratio. That is, if the transformer has half as many turns as the primary winding, then the voltage induced into the secondary will be half as great.

To check if the secondary winding of a low voltage transformer is working properly, perform a continuity test with an ohmmeter. If the ohmmeter shows high or infinite resistance, this indicates a break in the secondary winding of the transformer.

Primary winding

The primary winding of a low voltage transformer is used to convert an alternating magnetic field into an electrical current. The secondary winding is used to convert this alternating current into the voltage that you need.

The transformer’s core is not a solid bar of steel but rather is constructed by stacking laminated steel sheets, leaving a minimum air gap between them to provide a good conductive path for the flux to flow. This core also minimizes eddy current in its cross-section as a result of the fluctuating magnetic field.

Excitation energy is generated by the alternating current and is used to create a strong magnetic field in the core which links the windings together. However, this excitement energy is also dissipated in the form of heat (power loss).

Insulating materials

Insulating materials in low voltage transformers play a critical role in ensuring that power is transferred safely and efficiently. They must withstand sudden and large impulsive voltage surges.

They must also be able to withstand high dielectric stresses and resist breakdown. Breakdown can occur if the voltage exceeds a material’s “breakdown voltage.”

This means that the material has reached its maximum band gap, which is the highest energy electrons are able to be excited into. Once this is exceeded, electrical breakdown occurs and the material stops being an insulator.

In a low voltage transformer, the starting and ending windings are more thick than the remaining ones to resist such high impulsive surges. These windings are insulated with a specialized insulating oil that acts as an electrical insulator and a coolant.

Electronics

Low voltage transformers take the electricity running through the walls of your home and step it down to 12 or 24 volts so that you can run fixtures safely. They are commonly used for indoor and outdoor path lighting, under cabinet lights, doorbells and garage door openers.

The electronics in a low voltage transformer use electromagnetic induction to transfer electrical energy from the primary winding to the secondary winding. This is done by using a coil that has more turns on its primary winding than its secondary winding.

There are two main types of electronic low voltage transformers, stack laminated and toroidal. Stack/laminated transformers have sheets wrapped in copper wire laminated together to make a core.