Maquinas Eléctricas y Controladores
Aaron Farias Segovia 615484
This test is performed by runningthe machine as a motor at rated voltage and frequency with no connected
load. When separation of no-load losses is to be accomplished, run this test and read temperature, voltage,
current, andpower input at rated frequency and at voltages ranging from 125% of rated voltage down to the
point where further voltage reduction increases the current.
Bearing loss stabilization
Somemotors may experience a change in friction loss until the bearings reach a stabilized operating condi-
tion. In grease lubricated antifriction bearings, stabilization will not occur until there is noexcess grease
present in the path of the moving parts. This may require a number of hours of running to completely stabi-
lize the no-load input power. Stabilization can be considered to haveoccurred whenever the power input at
no-load does not vary by more than 3% between two successive readings at the same voltage at half-hour
intervals. This bearing loss stabilization test may not benecessary if a temperature test has been performed
prior to no-load testing.
The average of the line currents at rated voltage is the no-load current.
No-load lossesThe measured input power is the total of the losses in the motor at no-load. These losses consist of the stator
I2_R_, friction (including brush-friction loss on wound-rotor motors), windage, andcore losses.
Friction and windage
The friction and windage loss may also be determined by performing a linear regression analysis using three
or more lower points of the power versus voltagesquared curve. To determine the friction and windage loss,
subtract the stator I2_R_ loss (at the temperature of the test) from the total losses (i.e., input power) at each of
the test voltage...