Omron K7GE-MG User Manual page 92

4 Functions Related to Measurement
 When the Load Restarts
If the load restarts when applying a
Megger voltage, the voltage of the
power supply for driving the load is
applied between L3 and PE in the
figure shown on the right. If a current
limiter is not present, a large
short-circuit current will flow via the
Megger voltage generation circuit of
the K7GE-MG.
In such a case, the voltage monitoring function activates due to the generation of line voltage.
However, because of the intervening software, an instantaneous response of μ-second order cannot
be performed. Until that time, the overcurrent is limited by the current limiter.
 When the Drive Voltage
Becomes Zero While the
Contactor is ON
In this case, the line voltage is
zero. Therefore, the voltage
monitoring function judges that the
load is turned OFF.
If the Megger voltage is applied
even though the line voltage is
zero, the current flows in a path as
shown in the figure on the right
without passing through the insulation resistance of the load. If a current limiter is not present, a
short-circuit current will flow.
In either case, the current limiter will be operated immediately to avoid hazardous situations. If the
current limiter operates, the K7GE-MG immediately stops measuring and is cut off from the load, similar
to the voltage monitoring function.
Also, even when the current limiter activates, "measurement failed" occurs, and the alarm output turns
ON. Refer to Timing Chart for Measurement Failure on page 4-12 in 4-1-4 Timing Charts on page 4-8
for information on the operation when measurement fails.
4 - 24
MC
Note The above diagram shows only the parts of the internal circuit of the
K7GE-MG that are necessary for explanation.
Inverter
MC
Output zero
Note The above diagram shows only the parts of the internal circuit of the K7GE-MG
that are necessary for explanation.
Insulation Resistance Monitoring Device User's Manual (N224)
K7GE-MG
L2
Voltage Micro-
L3
monitoring computer
Current
Rz
limiter
Megger voltage
PE E
(50 VDC)
K7GE-MG
L2
Voltage Micro-
L3
monitoring computer
Current
Rz
limiter
Megger voltage
PE (50 VDC)