Potential Equalization Conductor vs Functional Earth Terminal

I have a class I medical device with a metal chassis and a type BF applied part, where the power inlet ground wire is attached to the chassis.

My first question would be what is the difference between a Potential Equalization Conductor and a Functional Earth Terminal.

And second is the Potential Equalization Conductor required?
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Not in medical, so only addressing one of the questions:

"potential equalization conductor: conductor other than a protective earth conductor or a neutral conductor, providing a direct connection between electrical equipment and the potential equalization busbar of the electrical installation"

From the IEC Glossary {emphasis added}.

I don't know about Medical, but in non-medical electronics, a separate "neutral" or "common" safety is required to avoid a backfeed voltage through the common wire. This goes from motor controllers all the way up through industrial building power supply.
Long and short, it's a separate safety mechanism to avoid shock.
Hello Shanerock,
It's all about the purpose of the connection, for what I know :
  • PE (protective earth) = safety
  • FE (functional earth) = electomagnetic compliance and compatibility
  • Potential Equalization = safety purpose, found mostly in medical devices operating in the patient environment to minimize potential differences between devices and objects
Physically, PE and FE are found in the C14 connector, the potential equalization connector is separated and is supposed to be plugged by the service personel when using the device, it should be written in the Manual.

Peter Selvey

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Super Moderator
Just to add, potential equalization is intended for "cardiac protected areas", where the heart might be exposed during surgery. Currents applied direct to the heart are about 1000 times more dangerous than to the body, or in other words very small currents, voltages are considered dangerous. As such, these areas usually have very low resistance bonding for all metal parts, and potential equalization for equipment in the area.

I think it can become a sales point (looks cool, also can pad out the device spec sheet) and it's cheap to add, so a lot of equipment has these terminals even though they are unlikely to be used in a cardiac area. They could also be useful in noise reduction, either if the equipment itself is noisy or is sensitive to noise. But that's not the original purpose.
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