Wednesday, December 21, 2016

Safety in medical electrical equipment starts with the power input

Medical technology uses a wide range of electrical equipment. During normal operation and in the event of a malfunction, it is imperative that the equipment does not pose any danger to patients or medical staff. A piece of equipment that causes a short circuit or residual current can trigger a protective system upstream and in doing so shut down other, possibly life sustaining, equipment. Thus, it is necessary to pay special attention to how each unit is supplied with power. Connectors and power entry modules used in the equipment are tested to component standards and if in compliance with these standards can generally be used in most equipment without additional testing. This is especially true for medical equipment, where extensive requirements regarding safety are in effect, as defined in the base standard for medical electrical equipment, IEC/UL 60601-1. In addition, there are a wide range of specific requirements for each category of equipment according to IEC 60601-x-xx. The IEC standards for medical electrical equipment are harmonized with UL so that the same requirements are also in effect for equipment in North America.


Medical devices can be connected directly to the mains or with a detachable power cord. Such plug connections must meet the requirements of Standard IEC 60320. Depending on the application, it is recommended to include a mechanism to protect against any unintentional removal of the plug from the equipment's power socket. SCHURTER offers the V-Lock cord retaining solution, a simple, attractive and alternative system to using brackets. With the V-Lock solution, the power socket is equipped with a notch that interlocks with a special latch on the connector on the power cord. The system prevents the cord from being pulled out of the socket unintentionally. The advantage of this solution is that no cord-retaining system specific to a unit's power socket or retaining bracket must be adapted and attached. SCHURTER offers a wide range of power cords with or without V-Lock for various countries. As part of the assortment, a «hospital grade» cord set is available for medical applications in North America.

As a safety test, the base standard for medical electrical equipment specifies a high-voltage test of 1.5 kVAC between L and N as well as between L/N and earth (PE). To PE, the 1.5 kVAC corresponds to the values of the filter standard and can be met without any problem. However, a filter between L and N should not be tested with 1.5 kVAC because its capacitors could be damaged. Therefore, here IEC/UL 60601-1 makes an exception for interference suppression capacitors, which can be removed for a high-voltage test if they have been tested to IEC 60384-14. All X and Y capacitors used in SCHURTER power-line filters are tested to IEC 60384-14, so no additional high-voltage testing is necessary. 

Furthermore, following fabrication, all SCHURTER power-line filters are subjected to a rigorous high-voltage test of at least 1.5 kVAC between L/N and PE; filters of Protection Class 2 are even tested to levels of 4 kVDC between the energized conductors L/N and the housing. SCHURTER offers a variety of Class 2 power-line filters for medical equipment designed for home use. Electrical equipment used in medical technology must fulfill high requirements in terms of safety. This protects both the patient and medical staff. This protection begins with the safe supply of electric power. SCHURTER offers a wide range of power sockets and power entry modules with and without power-line filters as well as filters for use in a broad range of equipment. 

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