New IEC medical standards address electrical hazards
The general standard IEC 60601 is the accepted standard for medical equipment, especially for medical electrical equipment and general requirements for basic patient safety.
The standard 60601 is a widely accepted benchmark series for medical electrical equipment and compliance with IEC60601 has become a de-facto requirement for the commercialization of electrical medical equipment in many countries.
IEC60601-1 3rd edition demands that two means of protection (MOPs), or isolation barriers exist where patients may come into contact with equipment. Key caption: AP = applied part; B(xx) Basic insulation (working voltage); D = Double insulation; LP = Live part; MP = Mains part; OP = Operational insulation; R = Reinforced insulation (working voltage).
The 3rd edition of this medical safety standard was first published by the IEC in 2005 (IEC60601-1:2005) and was adopted by the European Union in 2006 and published as EN60601-1:2006. The U.S. version was also published in 2006, but unlike 2nd edition, not by UL. It is published by the American Association for Medical Instrumentation (AAMI) and appears as ANSI/AAMI ES60601-1:2006. Canada published the standard in 2008 as CAN/CSA60601:2008.
Engineers need to be acutely aware that when using these standards, there are a number of key dates specified for the implementation of the 3rd edition, and that these vary by region.
In Europe, as of the 1st June 2012 the 2nd edition (EN60601-1/A2:1995) will be withdrawn, called the cessation date, and all products will need to be certified to the 3rd edition, EN60601-1:2006. This includes both new products introduced to the market and products already on sale.
The situation is rather different in the U.S. The cessation date for 2nd edition (UL60601-1:2003 1st ed) is 30 June 2013 but, unlike the EU, the FDA only requires that new products brought to market after this date will need to be 3rd edition certified (ANSI/AAMI ES60601-1:2005). In Canada the cessation date for 2nd edition (CAN/CSA C22.2 No. 601.1) is 1 June 2012, but again the 3rd edition (CSA?C22.2 NO. 60601?1:08) is only needed for products new to the market after this date.
Another complicating factor for designers is that the particular standards that are part of the 60601 family. These are commonly referred to as “part 2s” and will have the standard number 60601-2-xx, such as IEC60601-2-46, particular requirements for the safety of operating tables.
While the 2nd edition simply addressed basic safety issues to ensure freedom from any electrical, mechanical, radiation, and thermal hazards, it did not require devices to remain functional in that fail-safe was adequate, and compliance with test criteria relied upon a pass/fail result that did not take into account the essential performance of the device-under-test.
Recognizing these limitations, the 3rd edition introduces specifications for “essential performance” that require that equipment will continue to function as its designers intended throughout the test process.
Peter Blyth is Industry Director, Medical, at XP Power.