The MHV coaxial connection, also referred to
as miniature high voltage or high voltage
BNC’s, are ideally suited for medium to high
power applications with higher voltage
requirements. Caution should be exercised in
electrical systems fitted with both BNC and
MHV connections. BNC and MHV
connections are almost identical in
appearance and geometry and should never
be cross-mated since their electrical ratings
are not compatible. BNC connections are
rated for 500VDC while MHV connections
can handle voltages as high as 5000VDC.
The SHV coaxial connection, also referred to
as safe high voltage connections, are also
rated for service to 5000VDC. The difference
between these feedthroughs and their MHV
counterparts are the pin and contact
geometry. SHV cable connectors have
recessed female contacts with the male
mating pin located in the feedthrough. The
exact opposite is true with BNC and MHV
connections. SHV cable-connector center
contacts do not protrude beyond connector
ends as they do on an MHV. This makes the
SHV safer if accidentally powered while
disconnected. Additional coaxial feedthroughs, including SMA, SMB, SHV-15,
SHV-20, Triaxial, Microdot type and various
others, can be purchased directly from
Insulator Seal Site in Sarasota, Florida.
Power feedthroughs are used to transmit either high voltage, high current or a combination of both.
These products can be used for a multitude of vacuum applications including vacuum furnaces,
sample heating or biasing, in-vacuum coating applications such as electron-beam evaporation,
resistive heating evaporation, and DC plasma sputtering. Proven and time tested designs
Feedthrough families are employed to optimize the electrical performance of MDC power
feedthroughs. Where space is not a limitation ceramic surfaces are made as long as possible to
maximize strike and creep distances. If space is limited, ceramics are convoluted in
order to achieve increased surface distances with minimal impact on an insulator’s overall
length. Convoluted or fluted ceramics are recommended for environments where moisture or other surface contaminant may
hinder electrical performance of conventional straight wall insulators. All power
feedthrough air-side ceramic surfaces are glazed with a high temperature glass coating. This glass coating
reduces ceramic surface roughness and minimizes surface contamination thus enhancing an insulator’s
electrical surface tracking characteristics. The power feedthroughs offered in this
catalog are constructed with exposed, bare metal conductors on both the air and
vacuum sides. Connectors for these feedthroughs are available, but must be purchased separately.
Included in the MDC product line are tubular conductor feedthroughs that can be used to
transmit both power and coolants simultaneously. These products are referred to herein as
watercooled feedthroughs. Watercooled electrical components should be used with grounded,
closed-loop cooling systems and / or the use of nonconductive coolants such as deionized water or
ethylene glycol. Although inefficiently, tap water will conduct electricity. Water cooling lines must
therefore be electrically grounded and constructed of nonconductive material such
as polypropylene tubing. Properly grounded water lines will provide a safe dissipation
path for any power conducted by the water.
Watercooled power feedthroughs can carry higher current loads than solid conductors of
equal size and material when adequately cooled. Current or power ratings are not
given for watercooled feedthroughs because these ratings are dependent on a coolant’s
flow rate and its heat dissipating capacity. Since tap water temperatures can vary
dramatically from one location to another, so too will water’s heat dissipation capacity.
Users are advised to establish safe and practical coolant flow rates based on the
power requirements for their specific application and coolant heat dissipation capacity.
Breaks & Envelopes
Breaks and envelopes are tube like adapters with metal tube hardware bonded to the
ends of a ceramic tube. Components with diameters below and including 2.50 inches
are referred to as vacuum breaks, while those above are referred to as vacuum envelopes. The bonded metal tube ends
provide a means of attaching the breaks and envelopes to vacuum tube lines using flange
mounts or welding. The central ceramic portion of a break or envelope provides electrical insulation between
the two conductive metal ends. In other words, the ceramic produces an electrical break in an
otherwise continuous and conductive metal tube geometry.
The joining of ceramics to metals is a compromise between materials with dissimilar expansion
coefficients. Low expansion metals combined with careful joint design bring expansion coefficients to
an acceptable match and effectively minimize the stresses caused by differential
expansion between the ceramic and metal components being bonded. Minute variations
in expansion coefficients can be detrimental if ceramic to metal seals are subjected
to severe thermal gradients. The maximum recommended thermal gradient for any ceramic to
metal seal should not exceed 25°C per minute.
Multipin instrumentation refers to any feedthrough product containing more than
one conductor path or pin that is also fitted with fastening air-side connectors. These
feedthroughs are commonly used for the transmission of signal voltages and currents.
They are commonly referred to as instrumentation feedthroughs because of their use in
instrument control applications such as electron microscopes, electron-beam evaporation, electron
microscopy, surface science analysis and semiconductor process controls. MDC multipin
instrumentation feedthroughs are fitted with industry standard MS threaded circular connectors which
comply with MIL-C-5015 specifications.
Complete air and vacuum connectivity are standard with MDC’s new D-Subminiature
instrumentation feedthroughs. Nine, fifteen and twenty-five pin geometries are hermetically sealed using the latest in
glass-ceramic bonding technology. Air side connections are designed to interface with
standard off-the-shelf serial cable connectors. Vacuum connectivity is made possible with MDC’s unique
UHV compatible connectors and ribbon cables. These instrumentation feedthroughs provide the
same conveniences of circular type multipin products, but offer higher pin density in a
Connector accessories are available for most electrical feedthroughs.