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Cable selector
Three tools on one page. Cross-section: voltage drop and current rating for power cables. Current loop (instrumentation): the maximum cable length of a 4–20 mA loop, also with a barrier, isolator or HART. Cable selector: a few questions turn your requirements or specification into an enquiry line we can quote straight away. Indicative: not a substitute for a standards calculation or the specification.
Photo: Petar Milošević, CC BY-SA 4.0, via Wikimedia Commons
Indicative result
- Design current
- Minimum for voltage drop
- Minimum for current rating
- Voltage drop at chosen size
- Current rating at chosen size
- Table value and correction
Choose type, cores, CPR class and armour in the next step. Or have Q Cables verify and quote this straight away.
Assumptions
- Conductor resistance per IEC 60228 (maximum DC resistance at 20 °C), converted to the maximum operating temperature: 90 °C for XLPE, 70 °C for PVC. Reactance 0.08 Ω/km for multicore cable.
- Voltage drop: ΔU = k · I · L · (R cos φ + X sin φ), with k = 2 for single-phase and DC (out and back) and k = √3 for three-phase (line voltage). Percentage relative to 230 V, 400 V or the entered DC voltage.
- Current rating: IEC 60364-5-52, tables B.52.2 to B.52.5 for methods A1 to D2 and B.52.10 to B.52.13 for free air (E, F and G). Copper and aluminium, PVC and XLPE, 2 loaded conductors for single-phase and DC, 3 for three-phase. Ground tables at 2.5 K·m/W soil resistivity and 0.7 m depth.
- Correction factors: air B.52.14 (reference 30 °C), ground B.52.15 (reference 20 °C), touching groups B.52.17 row 1 (bunched; also for method C, on the safe side), B.52.18 (direct buried) and B.52.19 (ducts in the ground).
- Aluminium from 16 mm². Short-circuit withstand, protection, harmonics, diversity and parallel cables are not included.
This result is indicative and does not replace a calculation to NEN 1010, IEC 60364 or the project requirements. Our advice is an aid; the responsible designer or installer checks it and makes the decision. No rights can be derived from it.
Indicative result
- Core resistance at temperature
- Cable loop resistance (out and back)
- Total loop resistance
- Voltage at the transmitter
- Max. length at chosen cross-section
- Max. length per cross-section (voltage budget)
- HART window 230 to 1,100 Ω
- HART max. length (capacitance)
- Governing
Choose type, pairs, screen and CPR class in the next step. Or have Q Cables verify this straight away.
Assumptions
- Core resistance per IEC 60228 (maximum DC resistance at 20 °C; class 1 and 2 solid or stranded, class 5 fine-stranded), converted to the chosen ambient temperature at 0.393% per K.
- Two-wire loop: the current runs out and back through two cores of the cable. The screen is not used as return path.
- Voltage at the transmitter = supply voltage − fixed voltage drops (indicator, barrier diode) − loop current × (cable resistance + receiver + barrier + other). With a galvanic isolator the voltage at the field terminals applies and the receiver is not counted. The transmitter must keep its minimum terminal voltage at the highest loop current; take that value from the instrument datasheet.
- HART: total loop resistance between 230 and 1,100 Ω; maximum cable length L = 65·10⁶ / (R · C) − (Cf + 10,000) / C, with R the series resistance excluding the cable (Ω), C the cable capacitance core-core (pF/m) and Cf 5,000 pF per HART device. Capacitance presets are indicative; the cable datasheet prevails.
- Not included: cable inductance and the entity parameters for intrinsic safety (Ex i), ripple and tolerance of the supply.
This result is indicative and does not replace a calculation to the project requirements. Our advice is an aid; the responsible designer or installer checks it and makes the decision. No rights can be derived from it.
Recommendation · instrumentation
- Version
- Cores
- Sheath colour
- Alternative 1
- Alternative 2
- Length and delivery form
- To be confirmed
- Enquiry line
The quote form is then already filled in; you only add your details.
Assumptions
The recommendation is an ordering designation based on your answers, not a design. Our advice is an aid; the responsible designer or installer checks it and makes the decision. Indicative, not a substitute for the specification or standard; no rights can be derived from it.