Biomedical Engineering Reference
In-Depth Information
Controller
Computer
CM - I/O CD
(I/O Signal Line
Coupler/Decoupler)
Surge Main
Test Unit
Power
Cord
EUT
I/O Line
Figure 4.30
Setup for assessing the susceptibility of a medical device to high-energy power line
surges. Transients are applied to the ac power line leads as well as to I/O lines through the use of
coupling-decoupling networks. This tests simulates the transient variations in power line voltage that
may be induced by a lightning strike.
High-energy power line transients are not easy to generate without a pulse generator such
as the one described by the standard. Because of the voltages and energies involved, we rec-
ommend using a commercial unit. However, if you decide to build your own, follow the com-
ponent values suggested by IEC-61000-4-5, use conservative ratings, and above all, keep it
safe.
Susceptibility to Voltage Dips, Short Interruptions, and Voltage Variations
IEC-61000-4-11 covers power line voltage dips and interruptions. The voltage variations
and their duration are as follows:
• 30% Reduction for 10 ms
• 60% Reduction for 100 ms
•
95% Reduction for 5000 ms
•
10% Voltage variation
For this test, the performance of the device under test is assessed for each combination
of test level and duration selected with a sequence of three dips/interruption with intervals
of 10 seconds minimum between each test event. Each representative mode of operation
of the device under test should be assessed. For each voltage variation, a di
erent pass/fail
criterion may be used. However, the equipment must exhibit safe conditions following
long outages.
The implication of this test to designers is the need to provide energy reserves in the
equipment power supply to maintain operation through brief dips and outages, at least for
critical functions. Designers must also ensure that a device cannot power-up in an unsafe
ff
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