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ELV and SELV lightingWhat counts as extra-low voltage?
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- ELV
- Extra-low voltage: not exceeding 50 V AC or 120 V ripple-free DC. "Ripple-free" means a perfectly smooth DC line, not half-wave humps.
- LV
- Low voltage: above ELV, up to 1000 V AC (1500 V DC). The 230/400 V mains is LV.
- SELV
- Separated extra-low voltage, supplied through a safety isolating transformer, e.g. 230 V in, 12 V (≤ 50 V) out.
- Where you'll see it: under-cabinet and LED strip lighting, track lighting, media walls and garden lighting.
- ELV isn't automatically safe. You still need the right protective measures and must consider the environment.
- Why the grid steps voltage up: for the same power, higher voltage means less current, so less voltage drop over long distances. That allows thinner cables and fewer transformers.
- Transformer types include step-up and step-down (voltage), current, power and isolating.
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- 18th Edition
- Building Regs
- PAT
- Fundamental Inspection & Testing
- Initial Verification
- Periodic Inspection & Testing