Electrical insulation diagrams for IEC 60601-1 - why and how
A common question among medical device manufacturers is whether an electrical insulation concept or diagram is required by IEC 60601-1. The short answer is "No". The right answer is: "You should still make one". The early development of an electrical insulation concept is a tried-and-tested best practice for achieving a medical device that is both safe and compliant with the relevant standards from the IEC 60601 family.
Step 1) Draw a picture
Prepare a drawing giving the general overview of your device's electro-technical concept. A basic block diagram representing the areas with different voltage levels is a good starting point (e.g. mains voltage, secondary voltage, battery).
Then add parts relevant to the possibility of electrical shock. Here we find parts accessible to the user / operator (accessible parts) such as enclosures, buttons, accessible pins of signal-input/-output-part, ports etc. Furthermore, add applied parts that have to be in contact with the patient such as sensors, patient supports, instrument parts etc.
Step 2) Identify general requirements
Identify the applicable general requirements for separation of those parts, e.g. between enclosure parts and mains voltage parts in IEC 60601-1. The specification for such distances concerns creepage distances and air-clearances. Remember to consider dielectric strength test voltages for solid insulation materials.
Step 3) Dig deeper into the IEC 60601 standard series
Look into collateral standards (e.g. home healthcare in IEC 60601-1-11 or emergency care in IEC 60601-1-12) and particular standards (e.g. HF surgery devices in IEC 60601-2-2, ECG recorders in IEC 60601-2-25 or nerve and muscle stimulators in IEC 60601-2-10) applicable to your device!
There might be also be relevant requirements to consider, e.g. regarding the use of the protective earth connector or applied parts classifications.
Conclusion
Preparation of an electrical insulation concept and diagram is not rocket science! You will benefit from starting during the early stages of development, since it provides crucial technical requirements with high impact on further development tasks. As we all know, making fundamental changes in your device design late in the development cycle is something you want to avoid, due to the high costs such changes incur.
For the inexperienced, it can be difficult to identify the relevant standard requirements in IEC 60601 standard series due to its complexity. If you are not working with it every day, do not hesitate to get in touch with professionals!
About the Expert
Dr.-Ing. Benjamin Weber studied biomedical engineering in Lübeck and received his PhD in the field of calibration of pulse oximeters. In 2016, he joined KEYMKR GmbH and led the testing laboratory to it’s first DAkkS accreditation in 2018. Since 2020 he is head of the testing laboratory with a strong focus on medical electrical devices and the IEC 6060 standard series.
Keymkr, Lübeck Germany, are experts in Compliance Engineering, Technical Documentation and access to international markets. Keymkr also provides Product Testing (IEC 60601-1 and IEC 61010) for Medical Devices (MDR and IVD) and hosts an accredited testing laboratory.
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