MIL-DTL-22442/1C(AS)
10. Transformer tests. The following transformer measurements shall be made using the test
circuit of figure 6. Rl02 is a non-inductive, high precision (±1%) resistive load equivalent to the
nominal load impedance. R101 is a non-inductive, high precision resistance whose value shall
be chosen to be 40 to 60 percent of the nominal input matching impedance of the transformer.
Unless otherwise specified, the measurements shall be performed at 1000 Hz, and the rated input
voltage shall be applied across the primary winding of the transformer under test.
a. Transformer efficiency (power) measurement. The input power to the transformer shall
be determined using the test circuit of Figure 6 substituting voltage measurements as
indicated into the following equation:
(V 1) 2 - (V 2) 2 - (V 3) 2
Pin =
2 XR101
Then determine the output power by measuring the load voltage V4 using the equation:
(V 4) 2
=
Pout
R102
Pout
The efficiency of the transformer,
*100% shall meet the minimum specified in
Pin
Requirement 5.
b. Transformer input matching impedance measurement. The nominal input matching
impedance of the transformer shall be determined at 1000 Hz by substituting the values
obtained for V2 and V3 above into the equation.
.
V 3 R101
Z (input matching impedance) =
V2
c. Transformer distortion measurement. The total harmonic distortion (THD) of the
transformer under load conditions shall be determined using a distortion analyzer (see
6.8.1.4), of the general specification or by using a spectrum analyzer (see 6.8.1.3) of the
general specification to determine the amplitudes of the harmonics and using the
following equation
∑(A / A )
2
x 100%
THD (Total harmonic distortion) =
i
f
Where Ai is the amplitude of the ith harmonic and Af is the amplitude of the fundamental.
All harmonics within the range of 300 to 6000 Hz shall be considered. The distortion
shall be measured at fundamental frequencies of 300, 1000, 3000 Hz or as otherwise
specified by the qualifying activity to insure compliance with the requirements of
Requirement 7.
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