Leakage Reactance Test Procedures
3-2 72A-2243-01 Rev. B 9/04
September 17, 2004
NOTE For Single Phase transformers only, the Base Voltage in kV should be the
Line-to-Ground, and not the Line-to-Line, kV.
If available from previous testing the following additional benchmark
information should be entered:
• Benchmark percent impedance
• Benchmark percent reactance
If not, use the nameplate impedance in these fields.
Test Voltages
The objective is to select a voltage sufficient to allow an accurate
measurement of the leakage reactance. The source can be a 120 or 240 volts
outlet. The M4000 Leakage Reactance Interface can deliver a maximum test
current of 25 amperes for 3-5 minutes before tripping the output circuit
breaker. Its maximum continuous output current rating is 9.5 amperes. It is
equipped with a thermal shutdown circuit that prevents the output from being
energized in the event the variac autotransformer temperature has exceeded
the safe operating limit. The red overload light indicates overload.
If using the M4130 Leakage Reactance Module, choose a variac with the
ratings of the M4130 in mind (50 A, 400V).
Once you enter the transformer nameplate information (Percent Impedance,
and kV, MVA, and tap positions on which this number is based) and the
benchmark information, the M4000 calculates and suggests a test current. You
can then adjust the variac to the recommended test current.
If transformer nameplate information reference information is not available, a
test may still be run. However, if using the M4110, you must adjust the variac
so as to achieve at least 15 volts on the winding.
CAUTION Take care to assure all connecting cables are rated for the expected test
current. Since one of the windings will be short-circuited for this test, the
jumper cables must be rated for the expected current in the
short-circuited winding. Although the current cables used to energize
a winding will need to carry 25 amperes or less, the jumpers used to
short-circuit the opposite winding may be required to carry many times
this current.
Selecting the Test Method
The following approach to selecting the test type is recommended.
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