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Installation, Operation and Technical Manual
Rectifier Technologies
8. Maintenance
In this section some general routine maintenance procedures are described which should
be carried out to ensure that the equipment performs to the high reliability standards that it
has been designed to.
8.1 Warnings and precautions
Since the unit utilises high voltages and large storage capacitors, it is imperative to take
great care when working on the unit.
In particular, only qualified personnel should be allowed to service the units.
In addition, the following precaution should be observed:
Do not remove the cover with power on!
Allow five minutes to elapse after switch off before removing the cover
to make sure high voltage capacitors are fully discharged.
8.2 SMR Maintenance
Since the SMRs are fully alarmed and operate in an active loop current sharing
arrangement, there is no need for regular checks or adjustments of operating parameters.
However, some regular checks can be an early warning of problems waiting to happen.
8.2.1 Current Sharing
Under normal conditions, the output current variation from the average rectifier current by
every rectifier should be within ±2A or ±3%, whichever is less. It is possible however, for
internal loop parameters to change to such an extent that a unit does not share to the
extent that it should.
If the lack of sharing is extreme then either a CURRENT LIMIT or NO LOAD alarm will be
active and the operator should then refer to the next Section.
If, however, the current sharing is not so extreme as to generate an alarm, a regular check
of the current sharing among the rectifiers can lead to early detection of any units which
may be developing a fault.
In general, if only one or two units are "drifting", the most probable explanation is a
"drifting" component in the secondary control card of the SMRs involved. If, on the other
hand, many of the SMRs are not sharing satisfactorily, then the most likely problem area is
in the System Controller.
8.2.2 Integrity of Electrical Connections
It is good practice to check all accessible electrical connections at regular intervals to
ensure that no "hot spots" develop over time due to loose connections. An infra-red "hot
spot" detector is very useful for this function.
Alternatively, mechanical connections can be checked manually for tightness.
8.2.3 Fan Filter Maintenance
If fan filters are fitted it is important that they are removed and cleaned on a regular basis.
158-1872-01
76
19-Feb-14
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