Design note about a 75 KVA quiet power distribution system Page: 1 of 8
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Fermilab
TM-1252
2260.000
Design Note about a 75 KVA Quiet Power Distribution System
Age Visser
April 5, 1984
1. Subject
This note describes a 75KVA quiet power distribution system for X 653
in neutrino Lab D. It is fed from the regular AC distribution which
exists in the building and it has no standby power. Its purpose is
to remove electrical disturbances which are present on the regular AC
distribution.
2. Quiet Power Need and Cost
The need for well regulated and clean AC power distribution in
experimental area's increases when very sensitive electronic
detectors are used by experimenters. It is difficult to define how
much "noise" the detection equipment can withstand without giving
erroneous results. Electrical noise levels will most likely change
during the course of an experiment. A normal reaction is therefore
to install the maximum amount of safeguards against noise. However
quiet power distribution is expensive and should only be installed
where needed.
The total material cost - for this 75KVA quiet power distribution
system is about $20.000. This is lot of money and it is therefore
reasonable to ask the question: "Do we really need it?" I think that
there is no easy answer, but it is certainly wise to design and
install electronic equipment in such a manner that is is the least
susceptible to noise. It is not economical to eliminate all noise
completely and there will always be ground potential (noise)
differences of several volts at different building locations.
It is probably true that many complaints attributed to AC noise, in
existing installations, are the result of poor cable routing and
equipment grounding techniques, instead of AC line disturbances.
This could be especially true where distances between interconnected
sensitive electronic equipment, grounded at various points along the
way, are large. It is needles to say that clean AC power is only
part of the solution. The whole installation should be installed,
shielded and grounded properly, preferably at one point. This can be
a problem since the national Electric Code (Fermilab) requires that
all enclosures be grounded locally for personnel safety. Detectors
should be designed with this requirement in mind. Routing sensitive
cables away from noisy power cables and possibly shielding of
equipment are good practices. These preventative measures have
nothing to do with quiet AC power, but they can prevent a lot of
problems. Once a system is installed it is very hard to find out
where a problem comes from.
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Visser, A. T. Design note about a 75 KVA quiet power distribution system, report, April 5, 1984; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1412239/m1/1/: accessed March 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.