Understanding Electronic Transformers
Like a magnetic low voltage transformer, an electronic transformer contains an iron core and two sets of wires. It also has an electronic device inside of it called an inverter. The inverter enables electronic transformers to be much smaller and lighter than magnetic transformers.
Here’s How it Works:
Inverters in electronic transformers condition the current to change direction at a frequency of about 20,000-50,000 times per second (called 20,000-50,000 Hertz or Hz) as opposed to the “normal” power from your wall outlet, which changes direction at a frequency of 50Hz or 60Hz. The higher the frequency of the current, the smaller the low voltage transformer can be. Most electronic low voltage transformers provide high-frequency alternating current (AC) output. This high-frequency output means that there can be a substantial voltage drop if the wires carrying the high-frequency current are long, thin, or far apart.
How to Prevent Voltage Drop
As an electrical current travels farther and farther down the cable it can grow weaker, causing the bulbs on the end that’s farthest away to appear dimmer than the bulbs that are closest to the transformer. This event is referred to as voltage drop. To avoid a large voltage drop when using your AC electronic transformer, follow these tips:
- Use thick (low gauge) wires on the secondary/output side. The thicker the wire, the less the voltage drop you will experience.
- Keep the distance between the transformer and the lamp(s) as short as possible. The shorter the distance, the less the voltage drop you will experience.
- Try to use a pair of secondary wires that are twisted together in your electronic transformer. The closer the two output wires are to each other, the lower the voltage drop you will experience.
- When a low voltage transformer powers more than one fixture or circuit, split the output of the low voltage transformer immediately into several separate circuits rather than carrying all the power in one pair of wires. The less power per circuit, the less the voltage drop you will experience in your electronic transformers. (Ex: A circuit with a total of 300 watts of load will have a greater voltage drop than a circuit with only 50 watts of load.)
Note: Though there are exceptions to the rule, the great majority of electronic transformers output AC (alternating current) for xenon and halogen light fixtures. When you hear the term DC Transformer or DC Driver, it is typically referring to an LED Driver which is a power converter specifically engineered for the unique needs of LED lighting systems.
Using Dimmers with Electronic Transformers
Most electronic transformers are compatible with common incandescent dimmers. However, we recommend using a dimmer specifically designed to handle an electronic low voltage transformer to make sure you don’t lose dimming range and to avoid a hum during low light levels regulated by your low voltage electronic transformer.
How to Choose the Best Electronic Transformer
To make sure that you have the right electronic transformer for your lighting project, consider these key questions…
- Do you need a plug-in or hardwired electronic transformer?
- What wattage do you need?
Hint: The wattage of the electronic transformer should always equal or exceed the total wattage of the entire lighting system.]
- What voltage do you need? 12 volts or 24 volts?
[Hint: 24-volt electronic transformers are less common but can power longer runs (circuits) of lighting. However, 24-volt electronic transformers should only be used with lamps (light bulbs) that are rated for 24V. If a 24-volt electronic transformer is used with lamps that are rated for only 12 volts, the lamps will burn out immediately.]
- Do you need an electronic transformer that is encased (in a metal case)?
[Hint: The metal case provides a safe and convenient storage space for the electrical splices (terminal block connections). If you select an electronic transformer that does not come in a metal case, it probably should be stored in some type of metal housing (e.g., a junction box).]