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With regards to Clause 6.2.2 of IEC 62368-1:2018 (3rd edition), what is the failure criteria of PS1 under abnormal and single fault conditions on load and power source circuits?

In Clause 6.2.2.1, it is specified the electrical power source classification shall be determined by measuring the maximum power under each of the following conditions:

 

6.2.2.2 – Worst-case fault

6.2.2.3 – Worst-case power source fault

 

Therefore, PS Class (PS1, PS2, PS3) is determined by the above two measurements.

 

Worst-case (load) fault (6.2.2.2) represents any fault in the load circuit to draw maximum power from the power source.  In particular, the fault is ‘simulated’ by additional load as “LVR” shown in Figure 34.  The “LVR” is adjusted to draw maximum power from the power source while it is operated under normal operating condition. Note that single fault of components associated with the load is not actually conducted for Worst-case (load) fault.

 

However, in Worst-case power source fault (6.2.2.3), single fault testing (of components) is conducted in the power source circuit while the load is normally operated.

 

The criteria of PS1 as specified in 6.2.2.4, "power source measured according to 6.2.2 does not exceed 15 W measured after 3 seconds”, applies to the measurement results from both Worst-case fault and Worst-case power source fault.

 

Although the energy source of ES, MS, TS or RS in this standard is classified under Normal, Abnormal and Single fault conditions, PS classification is made by different method.

It is classified according to measured maximum power under Worst-case fault (6.2.2.2) and Worst-case power source fault (6.2.2.3).

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