Inverter Plug Wires and the Harness Behind Them
The short cable that links a string to an inverter input is not a separate product with its own mystery specification. On KUKA CABLE's own product list, inverter plug wires and wiring harnesses sit inside the PV division that has operated independently since August 2018, alongside DC and AC cable and solar connectors. The harness behind the plug is built from the same published cable: a 6 mm² tinned copper class 5 conductor to IEC 60228 in an electron-beam cross-linked XLPO sheath, rated DC 1.8/1.8 kV.
Key takeaways
- Inverter plug wires, PV cable assemblies and harnesses belong to the PV division that became independent in August 2018, together with DC cable, AC cable and connectors.
- The cable used for a plug wire carries the same published limits as a string run: DC 1.8/1.8 kV, test voltage 6.5 kV AC for 5 minutes, spark test 10 kV during production.
- The site lists solar connectors, solar fuse connectors, solar diode connectors and PV cable assemblies as separate pages, and a connector page carries a CE / RoHS certificate download.
- Heat limits as the maker publishes them run from −40 °C to +90 °C in ambient service, hold +120 °C for 20,000 hours, and reach +250 °C only during a 5-second short circuit.
What the plug wire really is
A plug wire is a finished assembly: a length of PV cable, two connectors crimped and mated to the manufacturer's stated tolerance, and a housing that keeps water and dust out of the contact. The manufacturer publishes solar connectors, solar fuse connectors, solar diode connectors and PV cable assemblies as distinct items, which is the clearest signal that the plug end is treated as an assembly rather than as a cut length of cable with something pushed onto it.
The cable inside is what sets the electrical ceiling. On the 1500 V solar cable page the conductor is tinned copper, class 5 flexible according to IEC 60228, with XLPO insulation and an XLPO sheath, both electron-beam cross-linked and low smoke halogen free, available in black or red. Rated voltage is DC 1.8/1.8 kV. A plug wire carrying that cable inherits the same published ratings and the same bending radius of 4 × the outer diameter.
Why the harness counts more than the connector brand
Most field failures blamed on connectors begin at the crimp. A contact pressed onto the wrong strand count, or onto a conductor that was twisted rather than seated, heats under load and slowly loses contact pressure. That is why the published strand detail matters: a 6 mm² conductor in the manufacturer's table is 84 strands of 0.29 mm, and a 4 mm² conductor is 56 strands of the same wire. A crimp die chosen for that fine stranding is not the same die used for a coarser class 2 conductor.
Two further published checks apply to the finished cable rather than the contact: a spark test at 10 kV during production, and a test voltage of 6.5 kV AC at 50 Hz for 5 minutes on the finished cable. Those are tests of insulation integrity. They do not prove a crimp, which is why the assembly has to be sampled separately and held to its own inspection routine.
Thermal behaviour at the inverter end
Inverter cabinets and combiner boxes run hotter than open racking, and the published limits are the same for cable and plug wire. Ambient range is −40 °C to +90 °C. On short circuit the insulation is published as withstanding +120 °C for 20,000 hours and +250 °C for 5 seconds. A poorly seated contact creates a local hot spot long before the ambient rating is reached, and the cable is then blamed for a joint it never touched.
Practically, that means the plug wire should be specified with the same care as the string run: same standard family, same conductor class, same temperature envelope, and a connector that is rated for the housing it is going into. The company's own certification list names TUV, IEC, CPR and others, with the certificates page counting more than 30 types including TUV, IEC, CE, SAA and UL.
Where the assembly sits in the wider range
- DC string cable, in single-core and twin-core versions, in the commonly used 4 mm², 6 mm² and 10 mm² sizes.
- AC cable for the grid side of the inverter.
- Inverter plug wires, connector assemblies and wiring harnesses.
- Energy storage cable, battery cable and the wider industrial range the company publishes.
The harness base was established in June 2021, which puts a date on when the assembly side became a separate activity rather than a service attached to cable sales. A buyer planning a full bill of materials for a utility-scale block can therefore source the string run, the plug wire and the connector from one solar pv cable range published by a single manufacturer instead of matching three suppliers' tolerances.
Published electrical and mechanical limits
| Parameter | Published value | Applies to |
|---|---|---|
| Rated voltage | DC 1.8/1.8 kV | Cable and assembly |
| Spark test during production | 10 kV | Finished cable length |
| Test voltage on finished cable | 6.5 kV AC, 50 Hz, 5 minutes | Finished cable length |
| Minimum bending radius | 4 × outer diameter | Cable and plug wire |
| Ambient temperature | −40 °C to +90 °C | Cable and plug wire |
| Short-circuit temperature | +120 °C at 20,000 h; +250 °C for 5 s | Insulation |
Worked example
Suppose a 100 kW block is wired with 40 strings, each needing a pair of plug wires of 2 m. That is 40 × 2 × 2 m, or 160 m of cable inside the assemblies. Using the published weight of 78 g/m for 6 mm², those 160 m weigh 12.48 kg before connectors are added. The packing, the cooling load of any reel, and the weight on the tray all follow from that figure, and the calculation is the author's own, made from the published table.
Check the voltage margin the same way. With a circuit rated DC 1.8/1.8 kV and a test voltage published at 6.5 kV AC for 5 minutes, the insulation is tested at a level several times the working voltage. That multiplication is the author's reading of the two published numbers, and it is the reason the assembly drawing should name the cable standard rather than only the connector part number.
Frequently asked questions
Can the same cable used for a string run be used to make an inverter plug wire?
Yes, in the manufacturer's published range the assembly products are drawn from the same PV cable family, so the ratings do not change. The 1500 V 6 mm² cable is rated DC 1.8/1.8 kV with a tinned copper class 5 conductor to IEC 60228 and an electron-beam cross-linked XLPO sheath. What changes is the assembly work at each end, crimping and housing, which is inspected as a separate operation.
Does the site publish minimum order quantities or lead times for harness work?
No. The manufacturer's website does not publish minimum order quantities, unit prices, lead times or shipping costs for cable or for harness assemblies. Those details have to be requested from the sales desk using the phone number and email address printed on every page. What the site does publish is the construction, the electrical limits, the test programme and downloadable data sheets.
What to put on the assembly drawing
Name the cable standard and the conductor class, state the rated voltage, give the connector type and the crimp specification, and set a sampling rate for pull and continuity checks on finished assemblies. Then ask for the published test voltage and the spark test level so the incoming inspection can mirror them rather than invent its own thresholds.
Finally, ask the supplier to confirm the standard family in writing: a TUV EN 50618 type build and a general-purpose cable build look similar on a bench and behave differently after ten years. Data sheets, the company catalogue and samples are available from the manufacturer on request, and the assembly pages sit beside the cable pages on the same site.
Descriptions of plug wires and harnesses here rest on the manufacturer's own website, kukacable.com, extracted 24 Sept 2026[1].