IEC 60601 - 8.8.3 Dielectric Strength test. 4kv being applied to the ground conductor?!

[Caio Amorim]

Hello everybody.

I have a dental chair being tested for the 60601-1 in the certifying body. We are having a non-compliance with item 8.8.3, dielectric strength test. The point being tested is between the primary and a BF type applied part, not grounded, for this reason the laboratory justifies the need to apply the 4kV in ground, phase and neutral conductor, short circuited, and in our equipment there are other parts, including PCB, being grounded, so there are many paths where dielectric strength is not sufficient to protect the applied part of the circuit being grounded.

In my understanding and in my research, I never saw this justification for 4kV being applied to the ground conductor. Does it make sense for the lab to test in this way or is it completely wrong?

 

[Benjamin Weber]

Usually phase and neutral are short circuited and act as one pole for the dielectric strength test. The other pole is then connected to the part under test, e.g. the applied part or enclosure. Actually it would be a very bad idea to connect the protective earth (ground in your case) to phase and neutral. This would always lead to failed test for enclosure part which are PE connected.
Either the lab is doing somethong totally wrong here or they explained it not clearly to you.

What applies for your applied part is the following:
- 2 MOPP between the mains supply and the applied part. This would be 4 kV (for 150 to 250 Vrms mains voltage) between phase/neutral and the applied part
- 1 MOPP between the applied part and other part incl. PE. If 4 kV are for 2 MOPP, then 1.5 kV are applied for 1 MOPP.
- 2 MOPP between the applied part and secondary circuits. I see maximum 24 V (dc?) in the diagram, so this would 1 kV.

I hope this helps?

 

[Caio Amorim]

Usually phase and neutral are short circuited and act as one pole for the dielectric strength test. The other pole is then connected to the part under test, e.g. the applied part or enclosure. Actually it would be a very bad idea to connect the protective earth (ground in your case) to phase and neutral. This would always lead to failed test for enclosure part which are PE connected.
Either the lab is doing somethong totally wrong here or they explained it not clearly to you.

What applies for your applied part is the following:
- 2 MOPP between the mains supply and the applied part. This would be 4 kV (for 150 to 250 Vrms mains voltage) between phase/neutral and the applied part
- 1 MOPP between the applied part and other part incl. PE. If 4 kV are for 2 MOPP, then 1.5 kV are applied for 1 MOPP.
- 2 MOPP between the applied part and secondary circuits. I see maximum 24 V (dc?) in the diagram, so this would 1 kV.

I hope this helps?

Thanks for your reply.

I saw it with my own eyes.
However, they test this way only for type BF applied part.