No.4 Business Building-2707, China Central Place
Chaoyang District, Beijing-100021, China
Email:info@daelim-electric.com
北 京 大 林 绿 源 环 保 科 技 有 限 公 司
BEIJING DAELIM GREEN EP TECH CO., LTD.
8. Factory Testing
CAUTION:
The information below is not intended to be as a guideline for testing transformers, please refer to
IEE/ANSI C57.12.90-2006 and
ANSI/NETA ATS-2009
for more details.
8.1 Routine Tests
Ratio
The turn ratio of a transformer is the ratio of the number of turns in the high-voltage winding to that in the
Lowvoltagewinding.Whenthetransformerhastaps,theturnratioshallbedeterminedforalltapsandfor
the full winding.
Note: The ratio test can also be used to test
polarity, phase relation, and phase sequence.
Winding Resistance
Resistance measurements are of fundamental importance for the calculation of the
2
R component of
conductorlosses and calculation of windingtemperatures at the end of atemperature rise test.
No Load and Excitation Current
No-load (excitation) losses are losses that are incident to the excitation of the transformer. No-load losses
include core loss, dielectric loss, conductor loss in the winding due to excitation current, and conductor loss
due to circulating current in parallel windings. These losses change with the excitation voltage.
Excitationcurrent(no-loadcurrent)isthecurrentthatflowsinanywindingusedtoexcitethetransformer
whenallotherwindingsareopen-circuited.Itisgenerallyexpressedinpercentoftheratedcurrentofthe
winding in which it is measured. The no-load losses consist primarily of the core loss in the transformer core,
which is a function of the magnitude, frequency, and waveform of the impressed voltage. No-load losses also
varywithtemperatureandareparticularlysensitive todifferencesin waveform;therefore,no-load loss
measurements will vary markedly with the waveform of the test voltage.
Load Losses and Impedance Voltage
The load losses of a transformer are losses incident to a specified load carried by the transformer. Load losses
include
2
R loss in the windings due to load current and stray losses due to eddy currents induced by leakage
flux in the windings, core clamps, magnetic shields, tank walls, and other conducting parts
Theimpedancevoltageofatransformeristhevoltagerequiredtocirculateratedcurrentthroughoneoftwo
specified windings when the other winding is short-circuited, with the windings connected as for rated voltage
