Filter
Top Products
Fig. 126 shows an example of a delta filter used for suppressing radio
interference.The apex of the filter must be connected to the ground.
More complicated filters are used in three-phase networks.
Avoid earth looping (all earth terminals to one point) and create
maximum distance between audio and lighting cabling. If audio and lighting
cables have to cross each other, it should be done in a perpendicular
way. In sensitive applications screening of cabling is necessary.
Lifetime
When used within the specifications, the various circuit components
will last for many years with no more failures than approx. 1 per cent
per year (except lamps and glow-switch starters).
Most of the time, failures in the gear components are caused by
external circumstances,such as wrong wiring or connections, short-
circuiting,extreme heat or humidity, mains voltage peaks, poor
maintenance and the like.
For example, capacitors for lighting installations with the VDE approval
according to VDE 0560 must achieve a lifetime of 30 000 hours at their
marked voltage (250 or 450 V) and their maximum case temperature
(85 or 100 ºC).Higher voltages will shorten the capacitor life as follows:
Voltage
1.15 1.25 1.30 1.35 1.40 1.45 1.50
(times V
mark
)
Lifetime (h) 8500 4000 2900 2000 1500 1100 780
A failure rate of 5 per cent is then accepted and the capacitance loss must
be less than 10 per cent for parallel and 5 per cent for series capacitors.
Temperatures above the marked maximum capacitor case temperature
will halve the lifetime of the capacitor for every 8 degrees increase.
Therefore, if there are too many failures with capacitors, the capacitors
may be too hot or the applied voltage is (temporarily) too high.
For glow-switch starters the number of switches is specified as 10 000
or more. Deviations are caused by the different starting currents of the
various lamp types.
For electronic starters, the most relevant factor is the allowed
ambient temperature or the maximum case temperature t
c
.
The specified temperature range is from -40 ºC till + 80 ºC. Exceeding
these temperature limits will shorten the lifetime dramatically.
311
5
132
Fig. 126. Delta filter used for
suppressing radio interference.
3.10 Electromagnetic interference
L
N
5 nF
5 nF
0.2 mF