Facilities Quality Service
BUCK AND BOOST TRANSFORMERS
ISSUE:
Misapplication of Buck and Boost Transformers.
BACKGROUND:
Buck and boost transformers are isolation type transformers which can be used as
an autotransformer for small adjustments in voltage (either up or down). On a
recent project, newly installed buck and boost transformers failed shortly after
being energized. The transformers were installed on an emergency feeder (the
source was approximately 2300' away in another building) to boost the voltage
back to normal due to the long feeder length. The feeder terminated in the buck
and boost transformers and then ran to the building's automatic transfer switch.
The emergency feeder was continuously energized (without load) while the
building's normal service was energized. Since there was no load on this
emergency feeder, there was no voltage drop and the boost transformers
increased the voltage in excess of the rating of the transformers and all three
failed.
RECOMMENDATIONS/CONCLUSION:
Manufacturer's recommendations caution against the use of buck and boost
transformers to correct long-line voltage drop where the load fluctuates. If buck
and boost transformers are used to correct voltage drop during peak load cycles,
dangerously high voltages may result under lightly loaded conditions. A spec writer
note will be added to Section 16461 'Transformers (Specialty), to alert designers
about the misapplication of buck and boost transformers.
FOR ADDIT IONAL INFORMATION:
Contact Jeffrey Steplowski at 202-565-5477 in the Consulting Support Service
(183A).
10 December 1999
FM-181A-DA103
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