ABB UZE Repair Manual page 3

Recommended practices
ABB recommends careful consideration of the following factors for service and repair
work on on-load tap-changers.
Do not repair an on-load tap-changer or motor-drive mechanism with a serious mechani-
cal or electrical fault without first consulting ABB.
Before you start any work, make sure that the personnel doing the job have read and fully
understood the Repair documents provided with the unit.
To avoid damaging the unit, never exceed the operating limits stated in delivery docu-
ments and on rating-plates.
Do not alter or modify a unit without first consulting ABB.
Follow local and international wiring regulations at all times.
Use only factory authorized replacement parts and procedures.
WARNING, CAUTION and NOTE
A WARNING provides information which, if disregarded, could cause injury or death.
A CAUTION provides information which, if disregarded, could cause damage to the equip-
ment.
NOTE: A NOTE provides additional information to assist in carrying out the work de-
scribed.
Safety precautions
Before any work is carried out on the on-load tap-changer:
Make sure that the transformer is disconnected and that earthing is properly carried
out. Obtain a signed certificate from the engineer in charge.
The relevant technical documents should be read and understood before any work is
started, and the procedures in this document should be followed at all times.
Before starting any work in the on-load tap-changer the protective motor switch and
the LOCAL/REMOTE switch must be set at "0".
Before starting any work inside the motor-drive mechanism, the auxiliary power must
be switched off.
N.B. The motor, contactors and heating element may be energized from separate
sources.
The hands or tools must be kept away from the contacts when making a manual or
electrical operation. The contact arm is operated by a spring battery and can cause
severe damage.
ABB recommends that only service engineers with appropriate skills regarding on-load tap-
changers carry out the repairs.
ABB recommends that only maintenance engineers trained by ABB carry out contact re-
placement.
WARNING
CAUTION
WARNING
CAUTION