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EMC requirements for medical power supplies

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An overview of the requirements of the 4th edition of IEC 60601-1-2

By Ron Stull, Power Product Marketing Engineer

While the original IEC 60601-1 standard has now been around for 40 years, technology has evolved and the environments in which medical equipment is used have become more complex. This led to the consideration of risks due to electromagnetic interference and to a collateral standard on electromagnetic compatibility.

In the following post we will look at IEC 60601-1-2 4e edition of the EMC collateral standard, its link with medical power supplies and its date of entry into force in each region.

IEC 60601-1-2 4e editing requirements

The underlying premise of IEC 60601-1 is the understanding and management of risks, which the 3rd edition developed by defining the electrical performance requirements for safe operation in terms of protective means for patients and operators. This mainly determined the insulation, creepage and insulation specifications for different classes of use. It should also be noted that edition 3.1 of the standard clarified some previous definitions in light of new technologies.

The 4e The EMC warranty standard continues to focus on risk analysis, but moves away from categories of equipment, such as “life support” and instead considers “intended use environments”. More specifically, it defines professional health care, home care and “special” environments. Professional covers the traditional use of medical equipment in hospitals and similar places where medical personnel are present, but which today are also subject to increased EMC challenges. Home use addresses both the needs of non-specialist users and situations where the power supply may be less stable. Special is a contingency for environments that may exhibit high levels of electromagnetic disturbance, including industrial sites or in a radiation therapy treatment room.

Providing immunity to the sources of interference that these environments can produce is key to the more stringent test specifications defined in 4e edition, as shown in the table below.

Main changes to immunity test levels from 3rd edition at 4e edition of IEC 60601-1-2

IEC 60601-1-2 4e editing and feeds

Apart from battery powered devices, it is not really possible to exclude power supplies from IEC 60601-1 regulations which apply to medical equipment. This emerges from the previous 3rd edition classifications for patient and operator protection where a distinction is made between equipment in the same room as a patient, versus equipment that comes in physical contact with the patient, especially in the event of contact with the patient’s heart, as with a defibrillator.

In the latter case, only IEC 60601-1 qualified supplies are acceptable and even then an additional isolation barrier is required between the power supply and the point of patient contact. Even excluding cardiac equipment, isolation requirements for other uses are likely to affect the specifications and performance of a power supply.

Likewise, the immunity requirements defined by 4e edition impact power supply design, so that equipment designers are best served to select medical grade power supplies that comply with both IEC 60601-1 edition 3.1 and 4e EMC standards edition.

Conformity to IEC 60601-1-2 4e editing

The overall schedule for compliance with the various editions of IEC 60601-1, including the 4e The EMC standards edition is fully detailed here. However, in general terms, Edition 3.1 is currently in effect in the United States, Canada, Europe, Japan, Korea and Brazil. Other countries in Asia and elsewhere may lag behind in compliance for home use, but if manufacturers produce equipment for export, they will need to ensure compliance in the end-user country.

This same argument applies to the need to respect the 4e edition of the EMC standard which came into effect according to a harmonized schedule in the United States, Canada and Europe, from January 2019. For an equipment manufacturer who sources from another manufacturer, the best solution to obtain keeping abreast of complex and evolving standards is for purchasing ready-made units. CUI offers integrated and external power supplies from 6 watts to 550 watts fully compliant with the 4e edition EMC requirements of IEC 60601-1. By selecting one of these pre-certified models, you can ease the burden of medical device design compliance.

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