The development of a good insulation diagram is an extremely useful practice as it helps you to define how your design meets the requirements of the IEC 60601-1 standard.

To find out a few important things related to insulation diagrams, check out the short video below.

The main purpose of insulation diagrams is to uniquely identify all insulation barriers and other protective measures that are related to protection against electrical hazards in a medical electrical system.

The term ‘insulation diagram’ is introduced in the test report forms published by IECEE and used by test labs. There is indeed limited guidance on insulation diagrams provided in the test report forms. Consequently, there are many different styles and ways of drawing an insulation diagram.

Insulation diagram model

An insulation diagram should be a graphical representation of the device, and all insulation barriers should be identified with letters.

Insulation diagram

If a part is connected to protective earth, the connection should be indicated by a large dot. Applied parts should be extended beyond the equipment enclosure and terminated with an arrow, whereas the parts only accessible to the operator are not terminated in an arrow.

Below is an insulation diagram of a piece of medical electrical equipment. This particular example consists of two devices, a power supply, a device with an applied part, and an operator accessible part. The power supply converts AC mains voltage to a 12 VDC supply. As you can see, all insulation barriers are identified by letters.

Identification of the IEC 60601 standard requirements

Prior to design and development, you should create an insulation diagram and identify the requirements for each of these insulation barriers. You can do this by looking up the requirements in the general standard.

The table at the top right corner of the image below identifies the classifications used to look up the requirements.

Insulation diagram 2

The larger table is where all of the values are added. Focusing on this, you will see that the farthest left column identifies each insulation barrier, A to G. The next column shows the required number of means of protection, either one or two. It also tells you if it is patient protection or operator protection.

Moving along to the third and fourth columns, these identify the working voltage relevant for each insulation barrier.

The fifth and sixth columns tell you the required creepage distance and air clearance for each insulation barrier. The next column identifies the dielectric strength test voltage, in case of solid insulation.

A step-by-step process

The purpose of the example in this article is to illustrate the differences between applied parts and operator accessible parts, and between mains parts and secondary circuits. The insulation requirements of IEC 60601-1 are quite severe to provide adequate protection to patients, which is why it is so important to identify them early in the design phase.

There are many ways to do this process, but this is a good model to help you to develop good insulation diagrams for your medical device. It can be tricky to identify the exact requirements by looking at the values for creepage, clearance, and dielectric strength test in the appropriate tables in the standard. The key is simply to take it step-by-step.

Would you like to know more about safety for electrical devices?

If you want to know more about the 60601 standard and safety for electrical devices, take a look at our online course Introduction to Safety for Medical Devices and IEC 60601. This comprehensive course has in-depth information and quizzes to test your knowledge and understanding. At the end of the course you will also receive a course certificate, which many auditors will be looking for.

Our online courses are frequently taken by competent authorities, notified bodies and medical device manufacturers and distributors.

Claus Rømer Andersen

Claus Rømer Andersen is an accomplished trainer, consultant and facilitator in the medical device industry. With a background in electrical engineering, he has worked with regulatory navigation, approval management, device testing throughout his whole career.

He is recognized as having a pragmatic and solution oriented approach to helping development teams focus on relevant issues throughout the entire product life-cycle.

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