This, combined with the power management company’s thorough understanding of the industry, means it can offer IT and data centre managers expert advice on interpreting the new standard to help them ensure operational safety and guarantee business continuity.
“The amends to IEC 62040 make it mandatory for UPS manufacturers to declare either rated short-time withstand current (Icw) or rated conditional short-circuit current (Icc) values for their products,” said Janne Paananen, Technology Manager, Eaton. “This is a welcome development as dependable information about these values is essential for designing power systems that will remain safe even under extreme fault conditions. However, whilst there are minimum required Icw and Icc ratings listed in the amendment, actual fault current levels in real installations often exceed these. It’s important that designers consider this when selecting products, ensuring that the products’ ratings exceed the site’s fault current levels and can therefore be used safely in the installation.”
To achieve compliance, UPSs with declared Icc or Icw values of 10 kA or higher must be laboratory tested with a specified current level available at the UPS input terminals, and with a short-circuit at the UPS output terminals. Throughout the test, the UPS must perform safely, without arcing or the emission of flames. Eaton’s product designs are already subject to very strict safety standards and so performed well under testing, exceeding the minimum requirements.
The rated short-time withstand current (Icw) covered by the new standard is the current that can be carried without damage for a specified short period of time. The conditional short-circuit current (Icc) – which is normally used when the UPS is protected by, for example, a fuse – is the prospective short-circuit current that can be withstood for the time it takes for the short-circuit protective device to operate. The ratings relate to the UPS’s low impedance path, typically a static switch with associated components such as fuses, switches and inductors, used when operating in bypass or line-interactive mode. The requirements apply to each individual bypass circuit, including internal maintenance bypass circuits.
