The Difference between MOPP and MOOP in IEC 60601-1 3rd

By Leo Cheong/ MWUSA
In 2005, the International Electrotechnical Commission (IEC) published the third edition of medical safety standard (IEC60601-1: 2005), to replace the original second edition (IEC60601-1: 1998). The main difference between the 2nd edition and 3rd edition is the insulation level. The 2nd edition is divided into BI (Basic Isolation), SI (Supplementary Isolation), DI (Double Isolation) and RI (Reinforced Isolation), and the 3rd edition of new IEC60601-1 is divided into two categories of MOPP and MOOP
The new IEC60601-1 3rd edition standard is the harmonized standard for medical electrical equipment that has been adopted globally, and published as the following versions:

USA:     ANSI/AAMIES 60601-1:2005
EU:       EN60601-1:2005
Canada: CSA-C22.2 No. 60601-1:08
The major impact of 3rd edition is the distinction made between the operator and patient. As result, Means of Protection (MOP) was introduced and it is further categorized into 2 different classifications, which are Means of Patient Protection (MOPP) and Means of Operator Protection (MOOP).

It is the responsibility of the medical product manufacturer to determine the likelihood of a patient coming into contact, and decide whether patient protection (MOPP) or operator protection (MOOP) to use. If the medical devices come into contact with patients, they must meet the insulation requirements of MOPP.
In either case, the insulation between PRIMARY to SECONDARY must meet at least 2 x MOP and at least 1 x MOP between PRIMARY to protective earth (FG) at normal conditions. It is shown in Figure 1.

The isolation, creepage and insulation requirement for MOPP and MOOP are different and provided in Table 1.
1 x MOOP 1500 Vac 2.5 mm / 2mm Basic
2 x MOOP 3000 Vac 5 mm / 4mm Double
1 x MOPP 1500 Vac 4 mm / 2.5mm Basic
2 x MOPP 4000 Vac 8 mm / 5mm Double

Creepage is the shortest path between two conductive parts measured along the surface of the insulation.

Clearance is the shortest distance through air between two conductive parts.

Generally speaking, MOOP follows the requirement guideline from IEC60950 and MOPP follows 60601-1 2nd edition.  IEC 60601-1 2nd edition did not categorize devices for patients or operators contacts, but this new concept was introduced in the 3rd edition.  For equipment used within the laboratory environment without contacting patients, power supplies that meet 2 x MOOP standards is normally sufficient.  Power supplies that meet 2 x MOPP standards provide the highest level of protection. It can be advantageous to specify a 2 x MOPP power supply because it can cover most of the medical applications.