LLT ENGINEERING · Application analysis
Published · Updated
M25 Power and Signal Connector: Mixed Contact Ratings
Selecting an M25 power and signal connector starts with the actual circuits, not the shell. This guide screens 2-8 contact and 20/24-pin ratings, reads 2+6 and 3+8 hybrid layouts as two separately rated circuits, separates conductor size from cable jacket OD, and lists what to confirm before a part number is fixed.
Scope and boundaries
Applies to LLT M25 circular connectors in 2-8 contact, 20-pin, 24-pin, and 2+6 / 3+8 hybrid configurations used as equipment power and signal interfaces. An M25 power and signal connector is only correctly specified when each contact group is checked against its own current, voltage, conductor range, and cable sealing window, because the two groups carry different ratings that cannot be merged. The public summary table supports first-pass screening; it does not confirm terminal assignment, the mating half, temperature rise under the actual load, or certification coverage for a specific part number.
Start with the actual loads, not the shell
Start with the actual load and cable, then check the interface. Shell size is a poor first filter for the M25: within one shell, the catalog spans 2-8 contact arrangements, 20- and 24-pin versions, and 2+6 / 3+8 hybrid layouts, and each arrangement carries its own rating. A drive motor may need three power phases plus a feedback pair; an automation module may need one supply and a dozen signal lines. Both can land in an M25, but on different arrangements with different duties.
Two rules follow. The 35 A series maximum belongs to specific low-count configurations and never transfers to denser ones. IP67 likewise applies per selected configuration, holding only with correct mating, locking, intact seals, the specified cable, and completed installation sealing, consistent with the IEC 60529 definition rather than as a blanket series property.
Sources: Technical applicability · IEC 60529 — Degrees of protection provided by enclosures · LLT public connector catalog
Read hybrid layouts as two separate circuits
A marking like 2+6 or 3+8 describes two contact groups inside one interface, not one rating. On the attached 90° catalog page, the 2+6 and 3+8 configurations are listed with a power group of 20 A / 250 V and a signal group of 5 A / 100 V. Straight and flange mounting versions are checked against their own catalog pages. Current, voltage, and wiring specifications are verified separately for each group, and the two group currents are never added into a machine-level rating.
The groups also differ in contact size and conductor range, so a cable suited to the power contacts may be wrong for the signal contacts. Contact count and face layout alone never imply mate-ability: viewing direction, keying, and pin or socket gender are confirmed together from the end-face drawing of the exact part number, not from appearance.
Sources: Technical applicability · LLT public connector catalog
Screen current ratings by contact count
The summary table below is the first-pass screen. The 2- and 3-contact versions list 250 V / 35 A with conductors up to 4 mm²; the 4-contact version holds 35 A but caps conductors at 2.5 mm²; the 5-, 6-, and 8-contact versions list 250 V / 20 A; and the 20- and 24-pin versions list 100 V / 5 A at 0.3 mm². Each row applies only to its own configuration.
Rated current is stated per contact or per specified contact group; simultaneous loading on multiple contacts, conductor size, ambient temperature, and heat dissipation all affect temperature rise. Treat the table as a filter, with the final check against the datasheet and a temperature-rise verification under the real duty.
If every circuit stays within the per-contact rating of the chosen contact count and the cable jacket OD falls inside the sealing range, the configuration can move to drawing review; if either condition fails or is still unknown, the configuration cannot be confirmed until the full part number drawing and test conditions are checked.
Sources: LLT public connector catalog · Technical applicability
Match conductor size and cable jacket separately
Conductor cross section is specified per contact in mm²; AWG is a gauge numbering system, and the two can be cross-referenced only through a verified catalog correspondence. Neither number describes the cable jacket: the jacket OD in mm decides whether the rear clamping and sealing structure fits. Equal conductor sizes can come with different jacket diameters depending on core count, insulation, and jacket material, so the two values are always checked as separate numbers.
A conductor at or below the configuration maximum only clears the electrical screen; the cable OD must also sit inside the sealing adaptation range, and it is not enough that the product maximum exceeds the cable OD. If the cable OD is outside the published range, do not assume a seal swap is allowed; confirm the sealing method against the model documentation first.
Sources: Technical applicability · LLT selection guide
Fix mounting, coupling, and contact gender as separate choices
Mounting form and contact form are independent selections. Front panel, rear panel, flange, and in-line versions describe how the interface lands on the equipment; pin or socket describes the contact itself, and an equipment-side socket also raises supply-direction and unmated-protection questions. Coupling is self-locking or threaded per model — the series documentation shows the threaded nut in black and the self-lock nut in LLT blue, with the exact structure per model — and self-lock versions are released by their own mechanism, not by pulling the cable.
Panel cutout, board thickness, and locking conditions follow the drawing of the exact part number; for in-line joints, leave room for mating travel and bend radius instead. End-face drawings are read with the stated viewing direction and keying datum, never mirrored to infer a mating relationship.
Sources: Technical applicability · Connection and wiring methods · LLT public connector catalog
Where each arrangement family tends to fit
For drive motor harnesses, the low-count power arrangements pair motor phases with feedback lines; the selection focus is continuous and peak current, signal definitions, and harness strain relief. For inverter peripheral interfaces, the focus shifts to actual AC or DC voltage, creepage and clearance, touch protection, and de-energized maintenance.
For custom automation with detachable actuators and functional modules, the 20- and 24-pin or hybrid arrangements consolidate many signal lines; the focus is the panel cutout, mating space, and service method. These are selection focal points from the series documentation, not validation results for a specific machine.
Sources: LLT selection guide · LLT public connector catalog
What to submit before a part number is confirmed
A configuration becomes orderable only when the equipment data can be checked against the drawing. Prepare the following before requesting samples or a quotation:
With these on hand, engineering can confirm the full part number, the end-face and mounting drawings, and which evidence applies to the exact configuration.
- Circuit list: voltage and current per loop, contact count, and which contacts carry power versus signal
- Conductor cross section per core in mm², or AWG with the catalog correspondence, plus the cable jacket OD in mm
- Cable length and tolerance, flexibility needs, exit direction, and far-end termination
- Mounting form, panel thickness and cutout, and the mating half or counterpart model
- Environment: rain, immersion, washdown, UV, salt spray, and temperature
- Certification documents required for the target market, requested per SKU
Sources: LLT selection guide · Technical applicability
Source parameters
| Contact count | Rated voltage | Rated current | Maximum conductor cross section |
|---|---|---|---|
| 2 pins | 250 V | 35 A | ≤ 4 mm² |
| 3 contacts | 250 V | 35 A | ≤ 4 mm² |
| 4 contacts | 250 V | 35 A | ≤ 2.5 mm² |
| 5 contacts | 250 V | 20 A | ≤ 1.5 mm² |
| 6 contacts | 250 V | 20 A | ≤ 1.5 mm² |
| 8 contacts | 250 V | 20 A | ≤ 1 mm² |
| 20 pins | 100 V | 5 A | ≤ 0.3 mm² |
| 24 pins | 100 V | 5 A | ≤ 0.3 mm² |
Frequently asked questions
Can the power and signal group currents be added into one total rating?
No. Hybrid layouts such as 2+6 or 3+8 are two separately rated contact groups — on the attached 90° catalog page, 20 A / 250 V for the power group and 5 A / 100 V for the signal group. Each circuit is checked against its own group; the numbers are never summed.
Does the 35 A rating apply to every M25?
No. The 35 A rating applies to the 2-, 3-, and 4-contact configurations; 5- to 8-contact versions list 20 A, and the 20- and 24-pin versions list 5 A. Each table row applies only to its own configuration.
Can two M25 connectors with the same contact count mate directly?
Not by contact count alone. Mating also requires matching interface dimensions, keying, pin or socket gender, coupling method, and terminal assignment, confirmed against both drawings and, where needed, samples.
Is IP67 valid once the connector is assembled onto the cable?
IP67 applies per selected configuration and requires correct mating and locking, intact seals, the specified cable OD, and completed installation sealing. Long-term immersion or high-pressure washdown needs separately verified configurations.