SKF AWAIV-12, Руководство пользователя

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Inductance, impedance, and phase angle measurement principles and
theory
The windings in a motor form magnetic poles, which allow the motor to generate torque. For
AC induction motors, the magnetic field from the stator windings interacts with the magnetic
field of the squirrel cage rotor to generate a shaft torque. For DC motors, the interaction of
the magnetic field from the stator field winding and the rotating armature winding also
generates a shaft torque. Likewise, the interactions of the fields generated by the windings
of a synchronous motor create shaft torque. The common agents in the different designs of
these motors are windings—loops of wire that, along with a current, create a magnetic field.
Windings—loops of wire—have physical properties of inductance and resistance. Each
specific coil or winding will have a characteristic inductance as well as resistance. Reason
would suggest that a problem in a winding should show up as a change in inductance and
resistance. Therefore, measurements of inductance and resistance are made to evaluate the
winding’s overall health; more specifically, to evaluate the winding’s ability to create a
magnetic field.
A short review of inductance and impedance in general is appropriate. In general, if a coil
with N windings is excited with a voltage source V, there will be a current I drawn from the
source.
Figure 111. Basic coil winding schematic.
Just how much current flows through the coil, and the phase relationship between the
voltage and the current depends on the resistance of the coil’s wire, geometry of the coil, the
number of coil turns, as well as the magnetic permeability of the material in the coil’s vicinity.
A graphical representation of the voltage and current is shown below:
Figure 112. Representation of voltage and current over time.
112 SKF Static Motor Analyzer—Baker AWA-IV User Manual
Motor testing theory and reference