ABB UZE Repair Manual page 15

Error condition
The on-load tap-changer
performs more steps than
ordered, or operates towards
the end stop.
1ZSE 5492-128 en, Rev. 4
Fault finding procedure
1. If the on-load tap-changer makes more than three
operations there must be a failure in the time relay for
the running through protection.
Check the time setting or replace the relay.
2. Check that the flywheel is free from grease. For infor-
mation about cleaning, see Maintenance Guide.
3. Check that the flywheel stops in its middle position
with a tolerance of ± 30 degrees. For information
about adjusting the brake, refer to section Disc Brake
in Maintenance Guide.
4. Check that the raise and lower contactors function
properly (see circuit diagram, Fig. 3, and contact tim-
ing diagram, Fig. 4).
5. Check that the starting contact functions properly
(see circuit diagram and contact timing diagram).
For information about adjusting the contact, refer to
section Starting Contact in Maintenance Guide.
6. Check that the maintaining contact functions prop-
erly (see circuit diagram and contact timing diagram).
Exchange of maintaining contact, see section 3.5.
2 Trouble-shooting
15