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Defib Protected Applied Parts: 4mm clearance/creepage?
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Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
Defib Protected Applied Parts: 4mm clearance/creepage?
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creepage distance, iec 60601 - medical electrical equipment, medical device electronics and electrical equipment, safety (general)
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  Post Number #9  
Old 16th April 2018, 10:27 AM
MedMartin

 
 
Total Posts: 23
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

Hi,

as I understand it, the 4 mm is also required within one applied part.
To use your example between ECG leads are also requirements for differential mode testing and energy reduction testing acc. to 60601-1.
Often there are resistors included in the ECG cable with adequate clearance and creepage distances and pulse handling capability. Then there is no requirement on the connector.

Best regards
Martin
Thanks to MedMartin for your informative Post and/or Attachment!

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  Post Number #10  
Old 18th April 2018, 09:10 PM
Peter Selvey

 
 
Total Posts: 878
Re: Defib Protected Applied Parts: 4mm clearance/creepage?

Would have been good to jump in early here.

The limit of 4mm in 8.9.1.15 is intended to keep the isolation barrier at the normal 4.0mm limit for BF-CF isolation, and ignore the 5kV pulse in cr/cl assessments. Without this clause, manufacturers could be asked for distances up to 126mm (5kV, table 12).

So it is a relaxation for most devices. There are two scenarios where it is not a relaxation: where a BF/CF device intended only for 100-120V regions would normally have a limit of 3.0mm, and for Type B equipment which has no BF/CF isolation, in this case 8.9.1.15 would represent a increased limit.

The distance only applies to the 1.5kV.4mm barrier between the applied part (ECG circuit) and other parts as is normally required for BF/CF classified applied parts. It does not apply between parts of the circuit, for example between RA and LA electrodes. The reason is a little complicated but it comes down to understanding the whole purpose of Clause 8 and means of protection. Any requirement inside of Clause 8 (8.7, 8.8, 8.9 etc) has to be tied back to a identified MOP used to meet 8.1 and 8.4.

That does not mean the distances between RA and LA (for example) before the voltage limiting device are not important. I have seen cases of connectors with 0.3mm clearance being used at this point which makes no sense. Generally, for a rounded pads, 1mm is enough to pass 5kV pulse without breakdown. But anyway, it is an risk/engineering decision, not a limit from Clause 8.
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