New Terms: The 3rd edition of 60601-1 has brought many changes to the electrical medical product compliance process. Perhaps one of the biggest changes is the replacement of the terms used for determining compliance for accessible electrical circuits. No longer is the term “SELV” used in 60601-1. It has been replaced with new terms that separately identify the protection means for the patient and the user (doctor, nurse).

⋅ “Method of Patient Protection” (MOPP) is defined as the “Means of Protection” (MOP) used to protect the patient from a shock hazard.

⋅ “Method of Operator Protection” (MOOP) is defined as the “Means of Protection” (MOP) used to protect persons other than the patient (doctors, nurses, & other non-patients in the vicinity).

Two Methods of Protection: Shock hazard protection has always required two levels of protection for all circuits that are considered “accessible”. This was previously part of the definition for the term SELV. However, this is not the case with the new MOPP & MOOP terms. Each level of protection is a MOPP or a MOOP. Consequently, circuits that are accessible must be protected as follows:

⋅ 2 MOPP: Patients are required to be protected by two “Methods of Patient Protection”.

⋅ 2 MOOP: All other users and persons in the vicinity are required to be protected by two “Methods of Operator Protection”.

MOPP vs MOOP: As with previous editions of the standard, “2” methods of protection are accomplished with Double or Reinforced insulation, with a single level of protection provided by Basic insulation. The big difference in the new edition of the standard is the new, lower level of requirements now allowed for MOOP.

⋅ MOPP: The base requirements for MOPP remains similar to those of the 2nd edition of 60601-1. They include Dielectric Testing the insulation forming the method of protection, verifying creepage & clearance distances are compliant with table 12, and insuring the earth connections that are used as a means of patient protection meet the P.E. requirements.

⋅ MOOP: MOOP protection requirements were adopted from the operator access requirements in the ITE standard 60950-1. As such, 60950-1 compliant parts are considered a MOOP acceptable protection method. This opens up a huge number of component options to medical product designers – especially with 60950-1 certified SELV output power supplies now being accepted as providing 2 MOOP for medical product applications.

Summary: While the terms have changed, the principals have not. Two levels of electric shock protection are still required for accessible circuits. The patient protection requirements remain similar to the previous edition with “2 MOPP” being the equivalent of SELV from the 2nd edition of 60601-1. The big difference is the creation of the non-patient category MOOP and the new 60950-1 ITE based requirements that allow use of 60950-1 certified components or applying 60950-1 based requirements for shock hazard protection except for patient protection circuits.


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