Insulation between Secondary Accessible Parts and Earth

#1
Hi. Can someone please explain to me why there is a need for insulation between Secondary accessible parts and earth when the secondary side is SELV? I can not see the logic in having it for a MOOP. I'm new to this so I may be missing something quite straight forward!

Regards

Aubrey

Would I be right in saying that the need for insulation between secondary and earth would be only for a MOPP?
 
Elsmar Forum Sponsor
P

PaulGr

#3
Hi Aubrey, welcome to the cove.

The basic rule is to have two MOP to prevent your accessible parts from exceeding the limits specified in 8.4. Without having seen your isolation diagram it is difficult to discuss the best place for those 2 MOP. Perhaps you could give a little more context (housing type, type of accessible part, etc.)

If your 'SELV' power supply already provides 2 MOP between mains and the accessible part, then the isolation between an earthed metal case and your accessible part could be only functional. Any other reactions?

Besides, the concept of SELV is not used within the context of 60601-1.
 

Peter Selvey

Staff member
Super Moderator
#4
The structure of the standard is to consider anything >0.1V dangerous, but then provide various exceptions or exclusions.

The basic exclusion for secondary voltages can be found in 8.4.2c.

However, completely aside from this, there is no particular reason to have 1 MOP from secondary to earth. Most Class I equipment has the secondary earthed.

Power supplies generally have the secondary floating but this is more for a functional issue (flexible) than a means of protection against shock. By leaving the output floating they allow the designer of the end product to decide if earthing is suitable and if so, the best place for earthing.
 
#5
Thanks for the replies folks. The more I re-read my question the more I wish I had worded it better, alot better!
On our power supplies we have basic from the output to earth but on further evaluation I believe this is to do with the patient being considered at mains potential in a SFC, this being the case then there is the need for basic from the output to earth of the power supply.
I'm amazed that I was so focused on SELV when, as has rightly been pointed out, it is not a consideration as anything over 0.1V is potentially dangerous for a patient which is why 60601-1 is concerned with the current available. Thanks again for the responses :)
 
Thread starter Similar threads Forum Replies Date
R Is insulation between F type applied part and other parts a must? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
W Insulation requirements between F-type applied part and enclosure IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
E Insulation diagram for ECG monitoring and diagnosis system. IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
R IEC 60601-1 - Magnesium oxide used for the electrical insulation of heating elements IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
K Doubt on insulation class of a device IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
W Insulation requirements of BF type infant skin temperature probe IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
M 2xMOPP insulation for Applied Part B. IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
Q Isolation/Insulation Diagrams - IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
V PCB internal insulation treated as insulation formed by insulating compound IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
W HF surgery device accessory insulation requirements IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
E Creepage distance accross insulation of step up transformer EU Medical Device Regulations 2
S Who compiles the Critical Component List, Insulation Diagram etc.? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
P Question on Table 6 "Test voltages for solid insulation forming a MEANS OF PROTECTION IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
P MOOP and insulation coordination IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
K IEC60601 3rd Edition Insulation Thickness for electrosurgical devices IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
N Cable Connectors - Insulation does not go all the way into the back of the connector Manufacturing and Related Processes 4
P IEC 60601-1-11 - Conversion to Double Insulation IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
N Insulation Diagram for Water Tub IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
W Is anybody familiar with IEC61010-1 Insulation Requirements? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
V External power supply with reinforced insulation as a simple secondary circuit? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
P Understanding IEC 60601-1:2005, Clause 8.1 b) - Short Circuiting Double Insulation IEC 60601 - Medical Electrical Equipment Safety Standards Series 13
R Determining Working Voltage - Drawing a Medical Device Insulation Diagram IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
W Insulation Grade for In Vitro Diagnostic (IVD) Device? IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
S Do insulation layers in double insulation have sequence requirement? IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
S Can enclosure of semiconductor or electrolytic capacitor provides basic insulation? IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
N Insulation Barrier Testing - According IEC 60601-1 IEC 60601 - Medical Electrical Equipment Safety Standards Series 22
T Insulation diagram for a medical electrical equipment IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
H Insulation of FRP (fiberglass reinforced plastic) Tanks Manufacturing and Related Processes 3
B Control Chart - Minimum point & average insulation thickness for Automotive Wires Statistical Analysis Tools, Techniques and SPC 9
A Medical device with NON medical PC - USB galvanic insulation ISO 13485:2016 - Medical Device Quality Management Systems 2
Moumen H Variations between ASTM A29 Standard for steel bars and Mill test certificates specs Manufacturing and Related Processes 1
N R&R for Differences between 2 measurements Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
S Distinction between a critical supplier and a Virtual manufacturer EU Medical Device Regulations 2
I Сorrespondence between hazards and risks ISO 14971 - Medical Device Risk Management 2
W What is the difference between TYPE B and TYPE BF? IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
T The difference between ISO 14644-3:2005 and ISO 14644:2019 Other Medical Device Related Standards 2
Q Terminal Lugs sizes - Difference between 225/24 vs. 275/24 lugs Manufacturing and Related Processes 2
T Relationship between ISO 9001 and ISO – IEC BS EN 870079- 34 2020 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
M Difference between "Production Trial Run" and "Run at Rate" IATF 16949 - Automotive Quality Systems Standard 8
Ron Rompen Surface Finish Correlation between Ra, Rz and Tp (bearing surface ratio) General Measurement Device and Calibration Topics 3
L MRA between EU and Switzerland - 1/2021 EU Medical Device Regulations 2
D Difference between Test Method Validation and Gage R&R Qualification and Validation (including 21 CFR Part 11) 18
K Joint approval between OEM and Manufacturer on Design Documents ISO 13485:2016 - Medical Device Quality Management Systems 4
C Is my software an accessory? Telecommunication between HCP and patients EU Medical Device Regulations 10
K Verify Software Architecture - supporting interfaces between items IEC 62304 - Medical Device Software Life Cycle Processes 2
E ASTM F2118 - Fatigue testing of bone cement - Changes between the 2003 and the 2014? Other Medical Device Related Standards 1
A What is the difference between Design Process, Process Design and Design Control? 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 2
R What's the major difference between Green Belt and Black Belt in term of training and project Six Sigma 3
DuncanGibbons How is the arrangement between Design and Production organisation envisaged? EASA and JAA Aviation Standards and Requirements 4
M Risk Analysis Flow - Confusion between ISO 14971 and IEC 62304 IEC 62304 - Medical Device Software Life Cycle Processes 8

Similar threads

Top Bottom