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INSULATION RESISTANCE MEASUREMENTS ON MOTORS
Figure 9 shows reading
the resistance to ground of
a three-phase motor wind-
ing. Since the three-phase
motors are internally con-
nected, it is only neces-
sary to connect one lead to
the motor lead and the
other lead to the motor
frame as shown.
Megohmmeter Models 1020 and 1025
Figure 9
MEGOHMMETER
MODEL 1020
Ω
DATA HOLD
OFF
ON
MΩ
TIMER
Man.
3 Min.
500 V
250 V
Ω
~
V
AC
TEST
MΩ
~
V
/Ω
AC
- Line
+ Earth
–
+
Figure 10
Figure 10 shows the windings of
a three-phase motor separated.
Sometimes this can be done at
the lead terminals, while other
times the end bells must be
removed to get at the lead wires
of the coils. By connecting the
megohmmeter as shown, the
phase
insulation
value can now be determined.
Read between phases "A" and
"B", then "B" and "C", then "C"
and "A".
MEGOHMMETER
MODEL 1025
M Ω
DATA HOLD
OFF
ON
MΩ
TIMER
Man.
3 Min.
500 V
!
250 V
1000 V
Ω
~
V
AC
TEST
MΩ
~
V
/Ω
AC
- Line
+ Earth
–
+
resistance
15
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