Overview - ISO 13476:1997 (Ignition coils: electrical characteristics and test methods)
ISO 13476:1997 specifies electrical characteristics and standardized test methods for ignition coils used for inductive energy storage in road-vehicle ignition systems with solid‑state switching. The standard defines the parameters to be measured, test conditions (ambient temperature (23 ± 5) °C, relative humidity 45–75 %), required test equipment and circuits, and the content of the test report. It is intended to provide reproducible, comparable electrical data for coil manufacturers, ignition-system designers and test laboratories.
Key topics and technical requirements
- Scope: Applies to ignition coils for inductive energy storage with solid‑state switching in spark‑ignited internal combustion engines.
- Primary parameters:
- Primary resistance (Rp) - measured by 4‑point or corrected 2‑point method and corrected to 20 °C.
- Primary inductance (Lpf) - leakage inductance measured with secondary shorted using an LCR bridge (1 kHz).
- Primary current reference time (tref) - measured under defined switching conditions to characterise saturation and switching behaviour.
- Nominal primary interruption current (INp) and primary clamp voltage (Uplim).
- Secondary/output parameters:
- Maximum secondary output voltage (Usm) measured with defined total capacitance and load.
- Ignition limiting load resistance (R15 kV) - load at which maximum secondary voltage equals –15 kV.
- Secondary voltage rise time (tsUr) - measured between specified voltage points (–1.5 kV to –15 kV).
- Zener discharge energy (Ezd), duration (tfzd) and peak zener discharge current (Izdm) - computed by integrating zener voltage × current over discharge.
- Test equipment and limits:
- D.C. supply stability: 13.5 ± 0.1 V (12 V systems) or 27 ± 0.2 V (24 V systems) with tight ripple/recovery specs.
- Oscilloscope rise time ≤ 35 ns and minimum bandwidth 10 MHz; accuracy requirements for voltage/current probes.
- High‑voltage probe input capacitance ≤ 5 pF and input resistance ≥ 100 MΩ.
- Test arrangements: Defined circuits for single‑ended and double‑ended coils, simulated cable capacitances (e.g., 25–55 pF depending on system type), and use of zener diode strings to simulate exhaust spark.
Applications - who uses ISO 13476 and why
- Ignition coil manufacturers - to characterize and declare electrical performance, ensure interchangeability and support product specifications.
- Vehicle OEMs and ignition-system designers - to match coils with switching electronics, spark-plug requirements and HT routing.
- Component and systems test laboratories - to run comparable, reproducible electrical tests and produce standardized test reports.
- Quality assurance and procurement - to verify supplier claims and establish acceptance criteria for production and incoming inspection.
Benefits include consistent performance data, predictable coil-switch interactions, and improved system reliability and safety.
Test report requirements (summary)
The standard mandates inclusion of measured values such as Rp, Rs, tref, Lpf, Usm (at Ctotal), R15kV, tsUr, Ezd, tfzd, Izdm, Uzd, plus test conditions (supply voltage, INp, Uplim) and test circuit.
Related standards
- Other ISO/TC 22 road‑vehicle standards and IEC electrotechnical standards for high‑voltage measurement and probes are relevant for full test-lab compliance and instrumentation selection.