Control and instrumentation cables carry millivolts and milliamps, not kilowatts, and that single difference changes almost every design decision. Conductor stranding is finer so the cable survives repeated tray bending; insulation is selected for low dielectric constant as much as for voltage stress; cores are laid up in pairs so induced noise cancels rather than accumulates. Put an unshielded 4–20 mA loop within half a metre of a 400 A contactor coil and the reading drifts by several percent. Choosing between screened, unscreened, twisted pair and overall screened is therefore an EMC exercise before it is a voltage-drop exercise.
Voltcore Cable has built control and instrumentation cable at its Yixing, Jiangsu plant since 2008. The KVV and KVVP families run to GB/T 9330 with IEC 60228 Class 2 or Class 5 conductors, the DJYPVP instrumentation range to GB/T 19666 sheath compounds, and thermocouple grades to IEC 60584-3 alloy and tolerance classes. Standard sizes ship in 15–25 working days from Shanghai or Ningbo at 500 m per size, with OEM drum marking, private-label sheaths and cut-to-length packing handled in-house across 32 production lines.
The K family of PVC control cable is the default wiring material inside Chinese-built switchgear, MCC line-ups and plant control panels. Rated 450/750 V and built to GB/T 9330, it covers 2 to 61 cores in 0.75–10 mm², with the type suffix telling you exactly what sits between the copper and the sheath: nothing for KVV, a copper wire braid for KVVP, a copper tape for KVVP2, Class 5 flexible stranding for KVVR, or XLPE insulation for KYJV.
See all 5 PVC Control Cable constructions →
Instrumentation cable carries the signal that the control system acts on, and its construction is defined by capacitance, crosstalk and shielding geometry rather than by current rating. Polyethylene insulation keeps mutual capacitance near 50–60 pF/m against 90–130 pF/m for a PVC pair, conductors are twisted into pairs with a short, controlled lay length so that an external field induces equal and opposite voltages in the two legs, and the screen is placed where the interference study says it belongs.
See all 5 Instrumentation & Signal Cable constructions →
A screen does one job: it gives interference a low-impedance path to earth that does not pass through the signal conductor. How well it does that job is measured by transfer impedance, in milliohms per metre, and that figure depends on two things engineers often conflate — the optical coverage of the screen and the resistance of the path along it. Coverage governs leakage at high frequency; resistance governs behaviour at power frequency and at the switching frequencies a drive produces.
See all 4 Screened / Shielded Control Cable constructions →
A thermocouple measures the temperature difference between the hot junction and the point where the thermocouple metal meets copper. Extend the circuit with ordinary copper and you simply move that reference point to wherever the copper starts — usually a terminal block at an uncontrolled temperature. Extension and compensating cable exists to move the reference junction to a known, stable place, and the alloy in the conductor decides how much error that move introduces.
See all 4 Thermocouple & Compensating Cable constructions →
Selection notes — Control & Instrumentation Cable
Does this control circuit actually need a screen?
Noise reaches a signal core in three ways: capacitively from an adjacent conductor at higher potential, inductively from a rapidly changing current, and through a shared return path. A 4–20 mA loop with a 250 Ω receiver resistor is far more tolerant than a 100 mV thermocouple signal, which is why screening rules differ by signal type rather than by cable price.
Screen the circuit when the run leaves a metal cubicle, shares a tray with power conductors, or sits downstream of a variable frequency drive. Keep signal and power cables separated by 300 mm, or by a grounded steel divider in a common tray; where neither is possible, specify a screened cable and terminate the screen correctly at both ends.
- Switching circuits (contactor coils, solenoids, interlocks) inside one cubicle: unscreened KVV is normally sufficient.
- Analogue 4–20 mA and 0–10 V loops: overall copper braid screen, 360° termination at the PLC end.
- Thermocouple and RTD signals: individual pair screen plus overall screen, because the signal is millivolt-level.
- Digital buses (RS-485, Profibus, Modbus): twisted pair with 120 Ω or 150 Ω characteristic impedance and a foil plus braid screen.
Braid screen or tape screen — which one belongs on a VFD lead?
Braid and tape screens are not interchangeable. A copper wire braid gives 80–90 % optical coverage and, more importantly, a low-resistance path along the shield, which is what matters at power frequency and in the 2–20 kHz range produced by a VFD carrier. It also stays flexible when the cable has to bend around a motor terminal box.
Copper tape or foil reaches 100 % coverage and costs less, so it performs better against fast transients and radio-frequency interference above roughly 1 MHz. Its thin section carries higher DC resistance, which raises transfer impedance at low frequency, and it works poorly where the cable is flexed.
- VFD output leads and long analogue runs: copper wire braid (KVVP, KVVRP).
- Panel-internal data and RF-sensitive runs in fixed installation: copper tape or foil (KVVP2).
- Both properties at once: foil for coverage plus braid for the low-resistance path, with a tinned drain wire.
- A pigtail screen termination adds roughly 10–20 nH and undoes the screen above a few hundred kHz — use an EMC gland or a 360° clamp.
How do I read the Chinese type designation on an RFQ?
The GB type code is a compressed specification, and reading it correctly avoids an expensive mismatch at goods-in. K means control cable, D (with J) means electronic computer or instrumentation cable. The letter after the type prefix is the insulation, and the position of P tells you where the screen sits.
Rated voltage follows the family: 450/750 V for the K control family, 300/500 V for the DJ instrumentation family. Suffixes then describe the sheath behaviour — ZR for flame retardant, WDZ for low smoke zero halogen, NH for fire resistant — and the armour code, where 22 is steel tape and 32 is steel wire.
- K = control cable; V = PVC; YJ = XLPE; Y = polyethylene; P = copper wire braid; P2 = copper tape; R = flexible Class 5 conductor.
- 22 = steel tape armour, 32 = steel wire armour, 23 = steel tape armour with PE outer sheath.
- DJYVP: polyethylene insulation, PVC sheath, copper braid over the laid-up bundle.
- DJYPVP: each pair screened individually, then the whole bundle screened again — the usual choice when a 24 V DC switching circuit shares a cable with analogue pairs.
What should a control cable enquiry actually state?
Most delays and rejections come from incomplete enquiries, not from manufacturing. A quote request that lists only a type code and a core count will get a price built on assumptions about conductor class, screen coverage and sheath compound, and those assumptions rarely survive a drawing review.
State the standard you are auditing against, and say where third-party witness testing is required. Voltcore holds ISO 9001, ISO 14001 and ISO 45001, with CE marking to CPR EN 50575 and TÜV Rheinland, UL and SAA approvals available on the relevant constructions; naming the required approval at enquiry stage avoids a second production run.
- Rated voltage, core or pair count, cross-section and conductor class (Class 2 stranded or Class 5 flexible).
- Screen construction: braid, tape, foil plus braid, individual pair screens, drain wire, and required coverage percentage.
- Sheath compound and behaviour: PVC, LSZH, oil-resistant, UV-stabilised, flame-retardant class to GB/T 19666.
- Drum length, drum marking, private-label printing, cut-to-length packing, and the port (Shanghai or Ningbo).
Request pricing across the Control & Instrumentation Cable range
Include cross-section, core count, voltage grade, route length and installation method — those five determine price more than anything else on the page.
- Engineer-reviewed before pricing
- Reference drawings issued with the quotation
- Free sample up to free sample up to 5 m