Figure 7-57.--Testing a three-phase stator for
shorts.
opens by deliberately shorting each coil. A buzz at
Figure 7-55.--Testing the polarity of field coils.
any of the coils indicates a closed circuit.
If you use a meter-indicating internal growler
THREE-PHASE STATOR TESTING
(fig. 7-56), a pointer deflection indicates a short; no
AND REPAIR
deflection of the pointer indicates an open circuit.
In testing stator coils as in testing dc armatures,
THREE-PHASE STATOR
you will find the most common troubles to be
REWINDING
grounds, opens, and shorts.
When tests or observation determine that a
The internal growler (fig. 7-56) is used to check
three-phase stator needs rewinding, retain data must
for shorts and opens on the inside of stators and
be recorded.
stationary fields, or on large armature surfaces where
an external growler cannot be used To make such
It is important to keep an accurate record of all
checks, connect the internal growler to the rated ac
the pertinent data concerning the winding on the
source. Run the internal growler over the coils of a
stator data sheet, as shown in figure 7-58. This
motor or generator and listen over for a buzz (fig. 7-
information should be obtained before stripping; if
57). When a shorted coil exists, transformer action
not, it can be obtained during the stripping operation
causes the growling noise. Coils may be tested for
in the same manner as for dc armatures.
MAKE
HP
RPM
VOLTS
AMP
HERTZ
TYPE
FRAME
STYLE
TEMP.
MODEL
SERIAL
PHASE
NO. OF
NO. OF
CONNECTION
COILS
SLOTS
SIZE WIRE
NO. OF
NO. OF
TURNS
GROUPS
COILS-
NO.OF
PITCH
GROUP
POLES
OF COIL
Figure 7-58.--Stator data sheet.
Figure 7-56.--Internal growler.
7-39
