FEATURE EMC & THERMAL MANAGEMENT THE ELECTRIFICATION OF MODERN MEDICINE
The medical electronics market is continuing to evolve, driven by the advance of wearables and the IoT, fueled by our aging population and our ever growing towns and cities. Therefore a much needed overhaul of our over burdened medical infrastructure is necessary to cope with demand. Holger Urban, product marketing manager at Schaffner International looks at how technology is providing a compelling answer
D
esigning customer centric medical solutions, whether it be for remote
patient care or critical professional medical applications such as robot- aided surgery, are all key drivers for the engineering community. Here the central challenge is to improve health without applying any additional risk to the patient. EMC is now considered to be one of
the most important design aspects that any new electrical or electronic system design needs to fulfill. It is therefore essential to consider integrating EMC filters as soon as possible in the development phase. Selecting the right EMC filter could save time and prevent additional costs further down the line. A good example of a medical
application with limited space is the automated syringe pump. Such pumps are directly attached to the patient through an insulating plastic hose. The medication delivery must be programmable and repeatable; this means that the control logic has to be reliable. That’s why EMC matters in order to ensure the pumps continue to operate as intended without interfering with (or being affected by) other pumps and equipment operating nearby (within a hospital for example). Therefore relevant EMC and safety
standards need to be fulfilled. The medical Standard IEC60601-1 focusses on major safety points; some of these are applicable to the mains power entry where Schaffner has a range of solutions.
SPECIFYING IEC60601-1 Here Schaffner offers a level of product certification which helps meet the safety requirements of European and U.S. legislations. The approval certificate for these filters according to IEC60939-3 includes a section where the filters compatibility to fulfill the requirements of IEC60601-1 is stated. “The FN92XX filters (B-types in
particular) comply with the requirements of the EN/IEC 60601-1 standard regarding creepage and clearance distances, leakage current and voltage withstand.” Medical EMC filters also have to be
32 OCTOBER 2017 | ELECTRONICS
PERFORMANCE LEVELS WITH REDUCED LEAKAGE CURRENT Schaffner offers standard solutions for different levels of leakage current requirements. In general the solution for medical applications is the so called B-type filters. These filters do not have any capacitance to PE and therefore do not add any leakage current to the system. It must be noted that the overall leakage current for the whole system needs to be determined, even with a filter which does not introduce any leakage current. With removal of (Cy) capacitance to
designed to allow the customer to fulfill MOPP and MOOP (Means of patient and means of operator protection) for any medical application. Depending on the level of insulation needed, design of a custom filter solution can be considered. The leakage current definition for
electrical medical devices is an important topic which has the same purpose of reducing the risk to the patient. There are number of different connections to consider. The most severe level within the standard is CF (Class C floating type connection suitable for cardiac application) applied part, which is limited to 10µA in normal condition and 50µA in a single fault condition. Considering parasitic effects in a system the filter should not introduce any additional leakage current. However in less critical applications, EMC filters with very low leakage current can be considered as well. Such filters have higher performance
compared to filters without any leakage currents. Leakage currents are directly related to the value of capacitors used in filters connected between Lines to Protective Earth (PE) (Y- Capacitors or Cy).
Figure 1 & 2:
Schaffner offers a level of product certification which helps designers to meet the safety requirements of European and U.S. legislations
PE, the overall performance of the filter is reduced compared to the standard filter with Cy. Schaffner also offers so called EB-type filter to compensate some of lost performance as a result of no Cy. In addition to the performance
enhancement, EB-type filters increase immunity to electrical fast transients compared to the B-type. This will help comply with the IEC/EN61000-4-4 immunity tests. Therefore Schaffner EB-Type Filters
can be the best performing filters available in its class for a reliable medical Electrical design. To conclude, EMC filters for medical applications should:
• Fulfill the most stringent leakage current regulations
• Offer the best size vs performance • Be designed for typical usage in
medical environment Overall its clear devices should help to
increase the health of patients and should not pose any potential risks when applied to a human body. With a Schaffner filter, it is easier to solve EMC issues and get product certifications without applying any additional risk to the patient. Schaffner not only offers a number of
“off the shelf” EMC filtering solutions for medical applications but also works closely with customers who require customised solutions.
Schaffner International
www.schaffner.com T: +41 32 681 66 26
/ ELECTRONICS
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