Low-voltage and safety-extra-low-voltage connectors: why there is no earth pin under 50V
Hand lamps, inspection lighting and damp locations use 20–50V connectors that look different from ordinary industrial sockets: no earth contact, and two keyways for mistake-proofing. The IEC 60449 definitions and the low-voltage models we stock.
Definitions first
Under IEC 60449, low voltage (safety extra-low voltage) means up to 50V AC or 120V DC. Below 50V the voltage is low enough that a protective earth contact is not required — which is why these connectors have one pin fewer.
No earth pin, so how is it made mistake-proof?
Instead of the earth pin there are two keyways, one main and one auxiliary: the main keyway is fixed at the 6 o'clock position and the auxiliary keyway is set by voltage and frequency, so low-voltage plugs of different voltages cannot enter each other's sockets. Positions 1 and 9 are reserved for future standardisation; positions 5, 6 and 7 cannot be used for mechanical reasons.
Low-voltage models we stock
| Voltage | Model | Specification |
|---|---|---|
| 20–25V | 1270 | 16A 2P IP44 |
| 40V | 1272 | 16A 3-pole IP44 |
| 50V | 9303 | 16A 3-pole IP67 (wall-mounted) |
| 50V | 1393 | 16A 4-pole (4P+N+PE) IP44 |
| 50V | 13248 | 63A 5-pole IP67 (plug) |
| 50V | 14248 | 63A 5-pole IP67 (connector) |
Typical use, and one warning
Common for hand lamps, inspection lighting, work in damp or confined spaces, on ships and inside vessels. Warning: safety extra-low voltage is not "safe to touch freely" — an isolating transformer is still required and cables must still be inspected. Low-voltage connectors are also not interchangeable at all with standard 230V/400V CEE devices, so never mix them.
Related: standards and colour coding · counting poles
Need a hand lamp or inspection lighting circuit? Tell us the voltage, power and location and we supply the transformer and connectors. Contact our engineers
