M
AVTMTTR330 Rev 3 March 2010
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3. When the fuse holder is installed in the single fuse position, apply the
screwdriver as shown and gently pry up. Use screwdriver as shown, do not
use fingers.
When the fuse holder is installed in the dual fuse position, it should normally
release as soon as the door is open.
Calibration
A complete performance and calibration check should be made at least once
every year. This will ensure that the TTR test set is functioning and calibrated
properly over the entire measurement range. The 3-phase TTR calibration is
performed on each new or repaired unit before sending it to a customer. There is
a special 3-phase TTR final calibration procedure which requires a NIST-
traceable test equipment to be used. As a result of such calibration procedure,
each TTR test set may be NIST certified.
To check the 3-phase TTR calibration at a customer site or in the field, the
Megger Calibration Standard Cat. No. 550055 or equivalent standard should be
used. To perform a quick simplified calibration check, the TTR Check Box Cat.
No. 550555 may be used. (Please note the one-digit difference in the catalog
numbers). The TTR Check Box has eleven switchable turns ratio settings which
cover the turns ratio range from 1:1 to 2000:1.
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