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Fault IV: lamp flickers.
• Possible cause:
- lamp operating voltage too high, end of lamp life,
- low supply voltage, check ballast connection,
- burning position out of specification.
Fault V: strong blackening of lamp, light output reduction.
• Possible cause:
- overload operation,
- wiring / ballast defect,
- capacitor across lamp instead of mains,
- end of lamp life.
Fault VI: fuse acting shortly after switch-on.
• Possible cause:
- fuse rating too low or not slow-acting type,
- wiring defect, overload operation.
Fault VII: colour differences in lamp colour.
• Possible cause:
- strongly varying burning positions in an installation,
- underload,
- lamps of different operating age or different suppliers,
- lamps of different colours used.
4: Electrical tests
Voltage and current measurements present the possibility of exposure
to hazardous voltages and should be performed only by qualified
personnel.To measure the correct effective values, true RMS voltmeters
have to be used. Measurements with non-true RMS meters can give
up to 50 per cent lower values, especially during measurements of the
lamp voltage or other non-sine-wave voltages (see table below).
Description Waveform True RMS Peak RMS Average RMS
calibrated calibrated
Sine wave 100 100 100
Square wave 100 71 111
Triangular wave 100 120 96
Single-phase
electronic load 100 200 50
current
Single-phase
electronic plus 100 166 83
30 % linear load
The parallel compensating capacitor can be measured in two ways:
1) Measure mains current and lamp current.
If both are the same, the capacitor is open-circuit and has to be
replaced.
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3.19 Fault finding