M12 Power Connector: S, T, L, K & C Coding Explained

On this page

• Quick Answer
• Why Power Has Its Own Codings
• The DC Power Codings: T and L
• The AC Power Codings: S, K and C
• Power Coding Comparison
• How to Choose an M12 Power Connector
• Power Codings in the Wider M12 Family
• Key Takeaways
• FAQ

Quick Answer

An M12 power connector uses one of the dedicated power codings — S, T, L, K or C — to carry AC or DC supply through the sealed, threaded 12 mm M12 form factor. The split is simple: T and L are DC codings, S, K and C are AC codings, each keyed so it cannot mate with a signal or Ethernet port. T-coding (DC, ~63 V, ~12 A) is the workhorse for DC supply to drives, I/O blocks and motors; S- and K-coding handle AC up to ~630 V. Because the codings differ in voltage, current and pin count, choosing the right power coding is the first step in specifying any M12 power connection.

Why Power Has Its Own Codings

The M12 family started with signal connectors, but the same rugged 12 mm body is just as useful for distributing power on a machine. Rather than overload the signal codings, the standard defines separate power codings so supply voltages travel on their own keyed connectors.

This separation is a safety feature, not just a naming convention. A power coding has a uniquely keyed insert, so an M12 power plug physically cannot be mated with an A-coded sensor port, a B-coded fieldbus port, or a D/X Ethernet port. On a machine carrying dozens of identical-looking 12 mm connectors, that keying prevents a higher-voltage power cable from ever reaching a sensitive input — exactly the kind of mistake that destroys equipment. Power codings also use larger contacts and wider spacing than signal codings, so they can carry the current and stand off the voltage that signal connectors cannot.

The DC Power Codings: T and L

T-Coded (DC power)

T-coding is the main DC power coding and the one you will meet most often. A T-coded M12 is typically a 4-contact connector rated to about 63 V DC and 12 A per contact — enough to carry roughly 750 W of DC power in a sealed, locking 12 mm connector. That makes it the standard choice for feeding DC supply to drives, remote I/O blocks, power distribution units, low-power DC motors and other field devices.

Because it is keyed for DC power only, a T-coded cable cannot be mated into an AC port or a signal port, which keeps the DC supply isolated from everything else on the machine. When you see "M12 power" on a modern DC installation, it is usually T-coding.

L-Coded (DC power, PROFINET profile)

L-coding is the DC power coding used in the PROFINET power profile. It carries DC at similar voltage levels — around 63 V DC — but is built for higher current, around 16 A, and is commonly found in a 4+PE (5-contact) arrangement. L-coding is the natural partner to D-coded PROFINET data: the network runs on the D-coded port and the device's DC supply arrives on the L-coded port, both in the same M12 family.

The AC Power Codings: S, K and C

S-Coded (AC power)

S-coding is the standard AC power coding, typically a 3+PE arrangement (three power contacts plus protective earth) rated up to 630 V AC at about 12 A. It is used for AC mains supply to drives, motors and machinery where a compact, sealed AC connector is needed in place of a larger industrial plug.

K-Coded (AC power, higher current)

K-coding is an AC power coding for more demanding AC distribution, typically a 4+PE (5-contact) connector rated up to 630 V AC at around 16 A — suited to three-phase AC supply for motors and drives. Where an S-coded connector runs out of headroom, K-coding extends the same sealed M12 approach to heavier AC loads. (Note: K-coding is AC power, not a high-pin-count signal connector — confirm the exact contact arrangement on the part's datasheet.)

C-Coded (legacy AC)

C-coding is an older AC coding, sometimes called "Micro-AC". It is used for AC actuators, AC sensors and similar AC devices, with anywhere from 3 to 6 contacts (commonly a 3+PE layout) and extended grounding pins plus a double keyway for added safety. C-coding is less common on modern designs than S, T, L and K, so treat it as a legacy AC option and confirm the specific part's rating against its datasheet rather than assuming a family figure.

Power Coding Comparison

| Coding | AC / DC | Typical contacts | Typical rating | Main use | |--------|---------|------------------|----------------|----------| | T | DC | 4 | ~63 V DC, ~12 A | DC supply to drives, I/O, motors | | L | DC | 4+PE (5) | ~63 V DC, ~16 A | PROFINET DC power | | S | AC | 3+PE (4) | ~630 V AC, ~12 A | AC mains to machinery | | K | AC | 4+PE (5) | ~630 V AC, ~16 A | Higher-current / 3-phase AC | | C | AC (legacy) | 3–6 | AC, see datasheet | Legacy AC actuators/sensors |

Ratings are typical figures per IEC 61076-2-111 and common manufacturer datasheets; the exact voltage and current depend on the specific part, contact material and cable, so always verify against the datasheet.

How to Choose an M12 Power Connector

Selecting a power connector follows a short, reliable sequence:

1. AC or DC? This is the first split. DC supply points to T (general DC) or L (PROFINET DC); AC supply points to S or K (or legacy C).
2. Voltage and current. Match the coding's rating to your load with margin. DC codings sit around 63 V; AC codings reach 630 V. Pick a current rating above your steady load, not at it.
3. Contacts and protective earth. Confirm the contact count and that a PE/earth contact is provided where the installation requires it.
4. Environment. Choose the IP rating and temperature range for where the connector lives — see the IP rating guide for IP67/68/69K differences.
5. Mechanical form. Straight or angled body, cable or panel mount, and pre-moulded cordset versus field-wireable.

Because power codings are not interchangeable, specifying the coding correctly up front prevents both ordering errors and the impossible task of mating a power cable into the wrong port. To filter the range by application and rating, use the connector selector, and for the wider coding picture see the M12 connector types guide.

Power Codings in the Wider M12 Family

Power codings sit alongside the signal and network codings that define the rest of the M12 range: A-coding for sensors and I/O, B-coding for PROFIBUS, and D- and X-coding for industrial Ethernet. The advantage of keeping them all in one 12 mm family is consistency — a machine can be wired for signals, networks and power using a single connector family, simplifying design, panel layout and spare-parts stock, while the keying guarantees the right cable always reaches the right port. For how power relates to the signal and Ethernet codings, see M12 connector types and what is an M12 connector.

Key Takeaways

• M12 power connectors use dedicated codings — S, T, L, K, C — keyed so power can never mate with a signal or Ethernet port.
• DC codings: T (general DC, ~63 V/~12 A) and L (PROFINET DC, ~63 V/~16 A).
• AC codings: S (~630 V/~12 A), K (~630 V/~16 A, higher-current AC) and C (legacy AC).
• Choose by AC/DC first, then voltage and current with margin, then contacts/PE, environment and form.
• Always confirm the exact rating against the part's datasheet rather than assuming a family figure.

Frequently asked questions

What is an M12 power connector?

An M12 power connector is a 12 mm threaded circular connector that uses a dedicated power coding — S, T, L, K or C — to distribute AC or DC supply voltage in a sealed, locking form factor. The power codings are keyed differently from signal and Ethernet codings so a power cable can never be plugged into a sensor or network port.

What is the difference between T-coded and S-coded M12 connectors?

T-coding is for DC power (typically 4 contacts, up to 63 V DC and about 12 A), while S-coding is for AC power (typically 3+PE, up to 630 V AC and about 12 A). Choose T for DC supply to drives and I/O, and S for AC mains connections.

How much current and voltage can an M12 power connector carry?

It depends on the coding. DC codings such as T and L are rated around 63 V DC at roughly 12–16 A, while AC codings such as S and K are rated up to 630 V AC at roughly 12–16 A. Always confirm the rating of the specific part against its datasheet.

Which M12 coding is used for DC power?

T-coding is the main DC power coding, rated to about 63 V DC, and L-coding is the DC power coding used in the PROFINET power profile. Both keep DC power on a keyed coding separate from AC and signal connectors.

Can I plug an M12 power connector into a signal port?

No. Each power coding has a uniquely keyed insert, so an S, T, L, K or C power connector physically cannot mate with an A-coded signal port, a D/X Ethernet port, or a B-coded fieldbus port. This keying is a safety feature that keeps higher voltages away from sensitive I/O.