The Diseases Of Electrical Machinery
Forfatter: Ernst Schulz
År: 1904
Forlag: E. & F. N. SPON, Ltd.
Sted: London
Sider: 84
UDK: 621.311
Edited with a preface, by Silvanus P. Thompson
Søgning i bogen
Den bedste måde at søge i bogen er ved at downloade PDF'en og søge i den.
Derved får du fremhævet ordene visuelt direkte på billedet af siden.
Digitaliseret bog
Bogens tekst er maskinlæst, så der kan være en del fejl og mangler.
ELECTRIC AL MACHINERY.
83
Example 2.
Continuous-current shunt motor, 50 horse-power,
110 volts, the same machine as was tested above as
dynamo. The values of the resistances are the same,
and also the current at full load. The magnet current
is, however, only 4 amperes. The no-load current is
still 15 amperes. We have the following losse»:—
Armature winding . . 725 watts.
Magnet winding . . 440 watts.
No-load . . . .1650 watts.
so that the efficiency at 50 horse-power is
___________50 X 746___________
(50 X 746) + 725 + 1440 + 1650
= O‘9i, i.e. 91
%•
Example 3.
Three-phase induction motor with short-circuited
rotor for 220 volts, 2 horse-power, 50 periods per se-
cond, 1500 revolutions per minute.
By measurement the current was found at no-load,
and at full-load, and also the electrical resistance of
one stator phase, i.e. of one third of the stator windings.
The no-load current was 2 • 22 amperes, the power
taken at no-load was 59 watts per phase ; therefore,
for all three-phases 177 watts. With 5 • 5 amperes full-
load current per phase, the power consumption was
600 watts per phase, i.e. 1800 watts altogether. The
electric resistance of one stator phase was 0*73 ohms.
There occur, therefore, the following losses :—