Hi Jose:
The voltage of the test generator is of no consequence.
The test is performed at 30 amps (for a 15-amp mains) into
a resistance not exceeding 0.1 ohm. According to Ohm's Law,
the voltage across the 0.1 ohm resistor is 3 volts.
On the other hand, if the potential is 12 volts and the
current is 30 amps, then the resistance is 0.4 ohms.
The requirement is for 0.1 ohm or less at 200% of the
rating of the overcurrent device. The generator will
never get to 12 volts (or 24 volts) during the test if
the equipment meets the 0.1 ohm, 200% requirement. I
don't know why the standard specifies the the voltage
of the test source.
But, if you are a certification house, then the test
equipment cannot exceed 12 volts (although I don't know
how one would confirm this except under open-circuit
conditions, which has no effect on the measurement).
With best regards,
Rich
On 3/29/2013 10:08 AM, Jose Moreno wrote:
Hello,
According to EN 60950, the resistance of the protective bonding
conductor has to be measured with a test voltage *not greater then 12V*.
Does anybody have a clue about the rationale for the 12V requirement?
If we measure the current and the voltage drop across the bonding
conductor, what difference does it make if we use 12V or 24V?
Thanks
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