The presence of internal horizontal partitions or barriers that obstruct airflow. 4. Calculating Air Temperature at Different Heights
Designing low-voltage switchgear isn't just about the electrical circuits—it’s about managing the heat they generate. IEC TR 60890
The full title of this technical report is "A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation" . It establishes an empirical procedure to determine the internal air temperature of enclosed assemblies, ensuring they operate within safe thermal limits. This method is primarily intended for: or partitioned sections.
The core of IEC TR 60890 is its systematic step-by-step method for verifying temperature rise. The process uses a simplified thermal network approach that relies on geometric data of the enclosure, the total power dissipation of the components, and the effective cooling surface area.
IEC TR 60890 is a technical report that provides a standardized method for verifying the temperature rise of air inside low-voltage switchgear and controlgear assemblies through calculation. This method serves as a critical alternative to physical testing, particularly for enclosed or partitioned assemblies without forced ventilation. iTeh Standards Core Purpose and Application Thermal Verification: iec tr 60890 pdf
IEC TR 60890 serves as one of those permitted alternative methods. It is officially referenced as a supplement to IEC 61439‑1 in many national adoptions, such as in the German DIN standard where the calculation method is described in of DIN EN 61439‑1. This close relationship makes IEC TR 60890 an essential tool for any manufacturer seeking to demonstrate compliance with IEC 61439‑1 through calculation rather than testing.
The primary objective of IEC TR 60890 is to offer a predictable, mathematically sound alternative to physical testing for specific enclosure configurations. Applicable Boundaries
: It assumes a relatively even distribution of heat-generating components inside the enclosure.
| Source | Price (approx.) | Key Features | | :--- | :--- | :--- | | (webstore.iec.ch) | 335.00 CHF | Official source, immediate PDF download available. | | Accuris Store (store.accuristech.com) | $367.00 USD | PDF immediate download, printed edition available. | | Techstreet (shop.standards.ie) | €267.36 (excl. VAT) for 2014 ed. [$8†L8] (Check for 2022 ed.) | Options for hardcopy, PDF, and multi-user PDF licenses. | The presence of internal horizontal partitions or barriers
Systems without (though the 2022 edition adds guidance for it).
Certification bodies (such as UL, CSA, VDE, or TÃœV) accept the TR 60890 method as a valid verification route for assemblies built according to IEC 61439. Auditors will expect to see the calculation sheets.
National standards bodies or authorized distributors like ANSI or BSI .
: When used under the umbrella of IEC 61439, it is strictly capped at a 1600 A rating. Higher currents require physical testing due to complex magnetic and skin effects. IEC TR 60890 The full title of this
The core of the IEC TR 60890 PDF is a series of tables. For a given power loss (P) and effective surface area (A_b), you read a base temperature rise value (ΔT). This value is then multiplied by correction factors for:
The first step involves calculating the sum of the power losses of all internal components, including: Circuit breakers, contactors, and fuses. Internal busbars and connection cables. Control electronics and power supplies. 2. Enclosure Cooling Surface Area ( Aecap A sub e
Using the calculated effective cooling surface area (Ae) and total power loss (P), the standard provides a graph or an algebraic equation to calculate the of the air inside the enclosure. This calculation gives engineers a reliable prediction of the internal ambient temperature.