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1ZSE 5492-129 en, Rev. 6
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1. Introduction
1.1 General
The UC range of on-load tap-changers manufactured by ABB has been developed over
many years to provide maximum of reliability. The simple and rugged design gives a service
life equal to the service life of the transformer. Minimum maintenance is required for trouble-
free operation. The only parts requiring maintenance are contacts that might need replace-
ment during the service life, the insulating oil and the motor-drive mechanism.
The design allows excellent access to all parts, making inspection and maintenance quick
and simple.
The on-load tap-changers, type UC, are housed in the transformer tank. The motor-drive
mechanisms, types BUE or BUL are attached to the transformer tank and connected to the
on-load tap-changer by means of drive-shafts and a bevel gear, see Figs. 1 and 2.
1.2 Repair categories
Repairs on the UC range of on-load tap-changers fall into two categories:
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Repairs. Repairs are to replace worn or end-of-service-life parts.
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Modifications. Modifications are only issued by ABB to improve the already very high
standard of reliability and to assist in prolonging the service life of the equipment.
The modifications fall into two areas:
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Immediate, where the modification should be completed at the earliest possible oppor
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tunity.
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Routine, where the modification should be completed during a routine service interval.
1. Introduction
