Introduction
Syfer Technology Ltd is a leader in EMI Filter
technology, providing products for surface and
panel mount applications.
As part of our product range extensions we are
now able to offer filters for power applications
where currents up to several hundred amps are
required.
Utilising plastic film technology the range includes
high ac and dc working voltage options along
with parts designed and tested to meet the
rigorous demands of EN132400/EN60950 safety
specifications.
Typical applications include IT servers, telecoms
base stations, MRI room equipment, power
supplies, radar and military vehicles.
Filters designed and tested to meet EN132400/
EN60950 class Y2 and Y4 requirements are
intended for use on mains supply systems or
lower voltage lines where safety is important.
Other products in Syfer’s EMI component
range include: surface mount feedthrough
capacitors and filters, panel mount ceramic
based feedthrough filters, X2Y integrated passive
components and LTCC multi element high
frequency filters.
Syfer is a world class manufacturer of surface
mount and radial leaded ceramic capacitors,
including safety and surge protection devices.
Syfer is also a leading supplier of discoidal
and planar ceramic capacitors to the EMI filter
industry.
syfer.com
Installation and technical notes
Background to Power Filters
Feedthrough filters offer high insertion loss performance from
kHz to GHz and high feedthrough currents to 100A+.
Stable, self-healing plastic film capacitors offering very low
series inductance and very high self resonant frequency and
through bulkhead mounting gives them a defined performance
advantage over board level or discrete component filtering
with traditional 2 terminal capacitors.
‘C’ Circuit filters (also known as feedthrough capacitors) offer
good general purpose performance at low cost. Improved
performance and sharper cut-off curves are achieved with the
use of Pi filters. Other package configurations (e.g. L-C or T
filters) are also available for low or mismatched source and
load impedances – please refer to the factory.
Typical applications include power input lines on IT servers
and telephone base stations or high performance power
supplies.
Safety
Care should be taken not to exceed the maximum rated
voltage and current for the filter.
Standard feedthrough capacitors rated at 600Vdc / 250Vac are
tested to either 1250V or 2250Vdc during manufacture which
can make them suitable for use in mains 250Vac applications,
but if operating safety is critical, or high transients are
anticipated, then the Y2 and Y4 class filters are designed and
tested to meet or exceed the test requirements of EN132400
and EN60950 including the 5000V DWV and 5000V peak pulse
testing requirements (Y2) or 2500V DWV and 2500V peak
pulse testing requirements (Y4).
All insulating materials are UL94 V-0 rated.
High currents will generate some heating effect, and particular
care should be paid to the current derating calculation shown
on each page. If current exceeds the maximum rating for the
filter, change to a higher rated device or talk to the factory for
possible alternatives.
All the filters in this catalogue are designed to operate at
high currents / high voltages and may be fitted with high
capacitances resulting in a potential electric shock hazard.
Electrical energy may be stored for some time after switch
off – do not handle filters without first discharging and / or
checking that the stored voltage is at a low level.
Construction
All Syfer power filters in this catalogue are manufactured
using self-healing polyester film wound capacitors and
incorporate a non-soldered construction for maximum
reliability.
Plastic film capacitors are used as standard and offer the best
mix of performance and temperature range, allowing high
volumetric capacitance and operating temperatures up to
85ºC (including self heating effect).
For specialist applications alternative plastic films can be used
to offer low dielectric losses or higher operating temperatures.
Please refer to the factory for further information.
Unlike some manufacturers, Syfer do not use oil impregnated
paper film capacitors which can catch fire or explode in the
case of failure.
Pi filters incorporate iron powder core inductors for maximum
performance with minimal degradation of insertion loss due to
high through currents. Declared performance is for full load.
Through conductors are copper alloy for maximum
conductivity with minimum loss or heating effect. Bodies
are brass or aluminium. All metal parts are nickel plated as
standard to present good electrical conductivity and anti
corrosion properties. All filters are resin sealed to protect
against harsh environments.
Failure mode
All the filters in this catalogue utilise plastic film capacitors
that will self-heal following break down due to excessive
voltage. The initial fail would be detected by a brief short
circuit transient followed by recovery to normal operation. If
the part is repeatedly subjected to over voltage transients,
then the capacitance will gradually decrease as the capacitor
operating layer is effected.
If a part is repeatedly driven to failure, subjected to a severe
over voltage condition or subjected to high ac voltages to
drive high ac current through the capacitor then a significant
heat build up can occur causing irreversible damage to the
capacitor which may result in a permanent open or short
circuit condition being generated.
RoHS compliance
All the filters in this catalogue are RoHS compliant.
Mounting
All these filters and capacitors are designed to be mounted
in a bulkhead or partition wall to achieve maximum high
frequency filtering performance through exploitation of
the Faraday cage effect. Filtering performed using discrete
components at board level will generally offer a lower level of
filtering performance as high frequency signals radiate over
and around the filter.
When mounting the filters, take care not exceed the maximum
mounting torques quoted as this may cause damage to
the metalwork or the internal components. All filters are
supplied as standard with the requisite nuts and washers to
successfully mount the part. When tightening conductor nuts,
use two spanners to prevent twisting the internal conductor
and risking damage to the resin seal.
Particular care must be taken to ensure good contact is
made to the through conductor, as high currents can result in
localised ‘hot spots’ through high resistive joints.
4
Custom Specials
Custom Specials
The vast majority of filters manufactured are customised to
meet the specific requirements of individual customers. Syfer
offer the option to manufacture to a customer specification or
to work together with the customer to develop a solution to
the problem.
If standard designs have been used for prototypes or initial
production, please talk to us about modifying the package to
suit your requirements to improve cost and ease assembly.
Prototypes can be arranged quickly and in small quantities to
solve particular problems.
Typical customisations include:
Multi-way packaging
Installing the capacitive and inductive elements of the
catalogue filters in a multi-way housing saves space and
cost as well as speeding the customers assembly into the
bulkhead. Typical packages would be 2, 4 or 8 feedthrough
filters to a single housing, but more can be accommodated.
Different housing design
Special designs are available to suit any particular customer
requirement. All standard filters are designed with round
bodies and a single, large mounting nut as the optimum
combination of cost and ease of mounting. Typical changes
include full hexagonal bodies to enable fitting in tight
spaces, or bodies with multiple mounting locations for critical
vibration.
Other options
•
Standard circuit configurations are C and Pi filters, but
L-C, C-L, T and multi-element (e.g. L-C-L-C-L) filters can all be
considered to suit particular applications.
•
Alternative materials can be considered – eg
Polypropylene or PPS plastic films can be used to offer low
dielectric losses or higher operating temperatures. Pure
copper conductors can be used to improve the current
carrying capacity or self heating effect.
•
Higher working voltages (to 1000Vdc typical) and higher
current carrying capacities (to 300A typical) are available.
5
Embedded System
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