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3) Short-circuiting of the ignitor
At the end of the lifetime of a glow-switch starter the bimetal electrodes
will stick together and will not re-open again.Then the short-circuit
current will continuously flow through the lamp electrodes, resulting in
strong lamp end blackening and a hot ballast.This effect often can be
found in practice if the maintenance of the installation is not well done.
It is advisable to renew also the glow-switch starter at lamp replacement.
4) Short-circuiting of the parallel compensating capacitor
This results in a complete short-circuit of the mains, so the mains fuse
will react. In fact, short-circuiting of the capacitor will not occur in
practice as capacitors for lighting applications must have a switch-off
mechanism that results in an open circuit during excessive capacitor
currents. In that case the circuit is not compensated,so the mains
current will rise.
Regular control of mains current and/or power factor is advisable.
5) Short-circuiting of the series capacitor
In fact there are no visible signs or critical effects when the series
capacitor is short-circuited.The lamp circuit will function normally, but
only the power factor will change and will shift.
3 Earth leakage
There are two different official earth classifications:
1) Protective earth (PE) with symbol ,which must ensure safety in
case of (human) contact with accessible metal parts that can become
live, e.g. at the end of the life of a component.
2) Functional earth with symbol , necessary to connect for reasons
other than safety.
With electromagnetic lamp control gear we only have to deal with
protective earthing,which is permissible by mounting the gear to an
earthed metal component.
Capacitors in metal housings can often be mounted by means of a
metal stud (see Fig. 141).
5
148
Fig. 141.Typical capacitor with metal
stud fixing.
3.18 Circuit breakers, fusing and earth leakage