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EMC FILTER IN MEDICAL APPLICATION

Posted by Holger Urban

EMC filters in medical technology - high performance thanks to a perfected design

Due to very high safety standards, medical devices must be equipped with special EMC filters. This inevitably entails performance losses. Selecting the right magnetic components and appropriate filter topologies helps to counteract these effects. Schaffner’s new filter family provides a highly performing solution.

Technologization and digitalization also affect medical technology. Not least, the changing demography and increasing demands of our society require a continuous expansion of the medical care.

As the international market leader for EMC filters, Schaffner permanently works on the development of efficient and powerful solutions for medical technology.


Compliance with safety standards

In medical engineering, the focus must be on the trouble-free functioning of devices. Whether life support is concerned or damage to health is to be avoided: in order that the devices used do not unintentionally affect the patients, compliance with safety standards is stringently required. One of these global standards is IEC 60601-1 which contains requirements for safety and performance features of medical devices.

Furthermore, guidelines for the direct handling of medical technology for operators (MOOP - Means of Operator Protection) and patients (MOPP - Means of Patient Protection) must be observed in order to guarantee absolute safety.

In addition to this safety standard, it is imperative to comply with standards on electromagnetic compatibility (EMC).


EMC - Electromagnetic compatibility

Electromagnetic compatibility deals with different propagation types and the suppression of interferences in an electrical system. The electromagnetic compatibility of a device describes its potential to neither influence an electromagnetic environment (source of interference) nor to be influenced by it (load).

Digital technology used in an analog environment must not interfere with other devices in the vicinity. In order to counteract malfunctions when operating electronic devices, certain statutory protection requirements must be complied with. Interferences typically occur in the conversion of voltages or in clocked applications and can spread either in conducted or radiated manner. Besides, common-mode signals and differential-mode signals are distinguished. In order to protect sensitive electronics against conducted signals, EMC filters are used for interference elimination.

FN9266-10-06 FN9262-1-06


How EMC filters work

EMC filters by Schaffner suppress interferences in the conducted spectrum (up to 30MHz). X and Y capacitors are used in devices to improve the interference immunity and to reduce the interference emission.

X capacitors are located between phase and neutral conductor of the filter. Together with the leakage inductance of the magnetic component they prevent differential-mode interferences. Y capacitors, in turn, filter the common-mode component together with the main inductance of the common-mode choke.

These filter topologies as well as their variations serve to meet different application-specific limits of interference emission required. The efficiency of a filter is measured and depicted in a standardized process. This also provides the opportunity to compare different filters. The result can be expressed in the so-called insertion loss in decibels (dB) via the frequency.

Typical filter attenuation

FN 9262_Standard Type 1A                  FN 9262_A Type 1A

FN 9262_B Type 1A

Leakage current in medical technology

In medical engineering, the leakage current plays an important role. A high leakage current poses a high risk to the patient. In order not to jeopardize the patient’s sometimes fragile health even more, it should therefore be avoided. Regarding the leakage current, certain statutory limits must be fulfilled. The leakage current values can only be complied with if the Y capacitors in the EMC filter are reduced. However, as already mentioned, the Y capacitors serve to compensate the common-mode interferences. The reduction of this important core component in the EMC filter automatically affects the performance of the medical device regarding its EMC compatibility, too.

Compensation by a magnetic component

This fact may only be compensated by using a magnetic component. In this respect you must be aware that, on the one hand, a filter provides only limited space, and, on the other hand, there is the risk that magnetic components might saturate at high interference levels. Should this be the case, they do no longer work as wanted. Increasing the impedance of a common-mode choke thus requires the use of higher-quality magnetic material, as it is used in Schaffner’s filter families FN9262 and FN9266. If you meet the expectations on the insertion loss in this way, i.e. using the filter in the interference path, you must additionally pay attention to the above-mentioned insulation requirements (MOOP/MOPP).

FN 9262                                   FN 9266

 

EMC filters in practical use

The powerful EMC filters by Schaffner find a use in a large number of medical applications. The high-performance EMC filters are applied, for instance, in automated syringe pump systems where they help to ensure a reliable and, above all, uniform supply of medicinal substances to the patient. For dialysis machines, too, EMC filters are used - here they make sure that the systems work consistently and without failure during the patient’s blood purification extending over several hours.

FN 9262 & FN 9266 – optimized for use in medical technology

By newly developing the filter families FN9262 and FN9266, Schaffner has achieved a differentiated classification according to MOPP1 for the so-called B-types (medical version). Furthermore, the filters comply with all filter-specific test requirements pursuant to IEC 60601-1. The high-performance filters have been developed in such a way that they can easily and broadly find a use in medical technology. Thanks to a perfect balancing of magnetic components and filter topology, the performance losses elsewhere usual can be avoided, while fully complying with the high safety requirements.

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