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|  MIL-M-17413A(NAVY)
4.2.4.18.2 Test records.- A record of radio noise tests indicating ambient noise, conducted noise
and, when required, radiated noise measurements and the date and location of tests shall be included in
the motor test records.
4.2.4.19 Weight. - The weight of motor and weight of armature shall be taken and recorded.
4.2.4.20 Efficiency. -
4.2.4.20.1 The efficiency shall be determined at rated load. In general, the efficiency shall be the
directly measured efficiency as determined by dynamometer. If test facilities are limited and the
efficiency cannot be measured by the foregoing method, the conventional efficiency will be acceptable. The
manufacturer shall state definitely in the test records if other than the directly measured efficiency is
given. A curve of efficiency plotted againsthorsepower output shall be made a part of the test record. The
efficiency shall be determined for 1/4, 1/2, 3/4, 4/4, and 5/4 rated load. Total losses at rated output
shall be segregated as follows:
12R fields
Brush contact loss
12R armature
Stray load
Field rheostat
Bearing friction and windage
Miscellaneous
Brush friction
Core losses
4.2.4.20.2 Copper losses. - The 12R loss shall depend on the measured current and the resistance
of the windings. For conventional efficiency the resistance of the windings shall be corrected to 75C,
For the directly measured efficiency these losses shall be based on the "hot" resistance of the windings
at the temperature of the windings under actual operating conditions.
4.2.4.20.3 Bearing friction and windage. - Drive the motor at rated speed from an independent
motor the output of which shall be suitably determined. The motor under test shall have the brushes
removed and shall not be excited. This output represents the bearing friction and windage of the motor
under test.
4.2.4.20.4 Brush friction of commutator. - Drive the motor at rated speed from an independent
motor the output of which shall be suitably determined. The brushes shall be in contact with the commuta-
tor, but the motor under test shall not be excited. The difference between the output obtained in the
"bearing friction and windage" test and this output shall be taken as the brush friction. The surface of the
commutator and brushes shall be smooth and glazed from running when this test is made.
4.2.4.20.5 Core losses. - Drive the motor at rated speed from an independent motor the output of
which shall be suitably determined. The brushes shall be in contact, and the motor shall be excited so as
to produce at the terminals a voltage corresponding to the calculated internal voltage for the load under
consideration. The difference between the output obtained by this test and that obtained under the "brush
friction of commutator" test shall be taken as the core loss.
4.2.4.20.6 Brush contact loss. - Two volts total drop shall be considered as the standard drop
corresponding to the brush contact loss, for carbon and graphite brushes with pigtails attached.
Three volts total drop shall be allowed where pigtails are not attached. Metal graphite brushes shall be
considered as special and hence require an actual determination of the drop in each case.
4.2.4.20.7 Stray load losses. - These include those iron and copper eddy-current losses not other-
wise included in the foregoing loss tests.
4.2.4.20.7.1 Where the efficiency is directly measured 2the stray load loss shall be the difference
between the total losses and the sum of the 12R of fields, I R armature, brush contact loss, bearing fric-
tion and windage, brush friction and core losses.
4.2.4.20.7.2 If "conventional" efficiency is given in lieu of directly measured efficiency; the stray
load loss shall be assigned a value of 1 percent of the output and this value used in determination of the
conventional efficiency.
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