Elk Training, Week 10

Transformers


What is a transformer? An inductor with two or more windings. The main winding is the primary; additional windings are the secondaries. A transformer uses mutual inductance from the primary winding to induce current into the secondary windings.
In Simple Terms:  The most common transformer in our industry is a "step down", class 2 transformer. It plugs into an AC outlet @ 120VAC (Volts Alternating Current) and "transforms" or "steps down" the voltage into a lower voltage, such as 16.5VAC or 24VAC.

When would you use one? Most security and some camera systems operate on 12 to 13.8VDC (Volts Direct Current). The power company supplies 120VAC which must be "stepped down", creating a need for a transformer like the ELK-TRG1640. The transformer "steps down" the 120VAC to a safer 16.5VAC which can then feed a security system or a linear power supply to provide 13.8VDC power.  Fire, Access Control, and some camera systems operate on 24 Volts requiring a 24VAC transformer like the ELK-TRG2440.

Why use a 16.5VAC transformer on a 12VDC security system? Two reasons: 1) there must be enough voltage to properly run the system and charge the back-up battery (approximately 13.8 volts)  2) there will be some power loss in the VAC to VDC conversion by the power supply. A 16.5VAC transformer (the most common transformer for security systems) will supply that extra voltage needed.
 
Note:  The term VA indicates Volt Amps or the available power. An ELK-TRG1640 transformer provides 45 VA @ 16.5VAC. A device requiring 20VA can be powered by a 45VA transformer. The device will draw only what it needs. Think about light bulbs; all operate on 120VAC, but the consumption varies - 40W, 60W, etc.

What makes ELK transformers different?  Most transformers contain non-replaceable fuses which, if shorted, blow and render the transformer useless. ELK designed their transformers with PTC short circuit devices that will shut off the current flow when shorted and restore full current when the short is removed. That is why ELK transformers come with a Lifetime over-the-counter warranty. Even though others now advertise PTC versions, only ELK provides a Lifetime warranty. Also, ELK is the only manufacturer to offer a grounding prong, grounding terminal, and wire strain relief. These provide the installer with an easy ground for the system.  
   
   
ELK-TRG1640 ELK-TRG2440
16.5VAC, 45 VA 24VAC, 40 VA
   
   

More Info
http://www.elkproducts.com/products/elk-trg1640_2440.htm
 

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