Hi Mike:
For a peak working voltage of 340 (240 rms), the routine test
(Table 5B) is 3000 V rms for 1 second between mains and ground.
(You do not have a peak working voltage exceeding 420 so Table
5B Part 2 does not apply.)
If you apply Table 5C, you must determine required withstand
voltage according to G.4 and G.2. You will likely end up with
the required withstand voltage equal to the mains transient
voltage, Table G.1, 2500 V peak.
According to Table 5C, if the required withstand voltage is
2500 V peak, the test voltage for reinforced insulation is
5000 V peak (3536 rms). This voltage can be reduced by 10%
to 4500 V peak (3182 rms).
So, you have a choice of 3000 V rms or 3182 V rms for 1 second.
Best regards,
Rich
On 8/6/2014 1:09 PM, Mike Cantwell wrote:
This seemed to me to be a simple question, but it's turned out to be
one with different answers from the experts, so I'm confused. Reading
section 5.2.2 of 60950-1, seems to say that an ITE product (computer
server specifically) that is Overvoltage Category II can use table 5B
to determine the test voltage, which is listed at 3,000 Vrms for
reinforced insulation for an ac mains of 240 Vrms (340 Vpk). I
understand that the working voltage in the power supply can exceed
this value and many of our CB reports definitely show this, but the
test voltage remains at 3,000 Vrms regardless.
Further along in section 5.2.2, it says that for routine tests, the
duration of the electric strength test can be dropped to 1 second and
the test voltage of Table 5C (different table) can be reduced by 10%.
But this table seems to imply that I can reduce the 3,000 V to a test
voltage of 2,700 Vrms.
Now table 5B (Part 2), for 340 V, the test voltage is 2,328 Vrms. If I
reduce this voltage by 10%, the test voltage is 2,095 Vrms. If I want
to do a DC hipot, the test voltage would becomes 2,963 Vdc.
I have been given numbers everywhere from 1500 V to 3000 V, and I'd
like to know what the proper test level should be. Is a different test
level determined for every power supply based on working voltage for
routine tests? or can one test level be determined and used for all
hipot testing.
As an EMC guy, the range I've been given by the safety folks is only 6
dB different and quite within the measurement uncertainty :) but
something tells me that the safety folks will have a better number for
the test levels and know the proper way it is derived.
I would like to set the hipot testers to a single value if at all
possible. Any help would be greatly appreciated on what the test level
should be for a routine hipot on a computer.
-
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