Differences Between MLV and ELV Dimmers
Dimmers for use with magnetic low-voltage transformers use a technology known as standard phase control or "leading edge," where as dimmers for electronic lowvoltage transformers use reverse phase control or "trailing edge." Standard phase control is for use with either inductive (MLV transformers, fans) or resistive (incandescent) loads. Reverse phase control is for use with either capacitive (ELV transformers) or resistive (incandescent) load types.
Reverse phase control or "trailing edge"
With reverse phase control, the dimmer starts to provide power immediately after the zero cross. Dimming is achieved by delaying the time at which the dimmer stops conducting.
Standard phase control or "leading edge"
With standard phase control, the dimmer does not provide power until sometime later into the line cycle. Once the dimmer starts to provide power, it will do so until the zero cross. Dimming is achieved by delaying the time at which the dimmer starts conducting.
Dimming Magnetic Transformers
Why Use Lutron Magnetic Low-Voltage Dimmers?
Magnetic transformers are inductive loads and are sensitive to DC voltages. A magnetic transformer subjected to DC voltage can overheat.
Do not use regular incandescent dimmers for magnetic low-voltage lighting. Regular incandescent dimmers often contain a small amount of DC voltage, which is harmless to a regular incandescent load but may damage magnetic transformers. Lutron MLV dimmers are specifically designed to prevent DC voltage from being applied to the transformer.
Certain MLV transformers may not be compatible with all Lutron dimmers. MLV transformers with built-in input chokes or "debuzzing coils" may not be compatible with certain microprocessor based dimmers. In order to address this compatibility, Lutron offers microprocessor dimmers with a neutral connection. Check with Lutron's Customer Service or your local Lutron representative for availability. These transformers should be compatible with standard (non-microprocessor) two wire controls such as Diva®, Nova T ® and Skylark®.
Some MLV transformers have secondary side protection such as PTC, fuses, circuit breakers or in some cases an electronic overload/fault detection circuit. In almost all cases PTCs, fuses and circuit breakers are compatible with Lutron dimmers. Check with the Lutron Technical Support Center for compatibility, especially with MLV transformers equipped with electronic overload/fault detection circuits.
A dimmer controlling an inductive load such as a magnetic transformer is also subjected to large voltage spikes and current surges. Lutron magnetic low-voltage dimmers are designed to withstand these spikes and surges.
The stated VA (volt-ampere) rating is the rated capacity of the magnetic low-voltage dimmer. The wattage rating is provided only as a reference and indicates the lamp wattage that can be placed on a UL approved (80% efficient) magnetic low-voltage transformer without exceeding the dimmer's VA rating.
Magnetic Transformer Wiring
Typical wiring for magnetic low-voltage dimmers.
Wiring for a Nova® magnetic low-voltage dimmer (NLV- 600, NLV-1000, NLV-1500). Note that only the Nova® single pole, slide-to-off Series requires a neutral wire.
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