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9 Power Backup System
MITSUBISHI CNC
9.4.6 Trouble Shooting at Power ON
If the drive unit does not start up correctly and a system error occurs when the drive unit power is turned ON, the power
backup unit may not have been started up properly. Check the LED display on the power backup unit, and take
measures according to this list.
LED
display
Symptom Cause of occurrence Investigation method Remedy
None PFU unit fails to start.
PFU's internal fuse is
open.
Check whether the power voltage is
properly input to L1, L2 and L3.
If voltage is properly input, replace
the power backup unit.
b
Unable to cancel emergency stop.
External emergency stop is occurring
on the power supply unit. (The LED on
power supply unit shows "q".）
Disconnection of the DO3
signal of CN43.
Check if the DO3 signal of CN43 is
correctly connected to CN23A of the
power supply unit.
Connect correctly.
Check if the 24V power supply of
DO3 signal is correctly connected to
DO_COM terminal.
Connect correctly.
1A
Unable to cancel emergency stop.
External emergency stop is occurring
on the power supply unit. (The LED on
power supply unit shows "q".）
Disconnection of the
resistor unit or an illegal
resistance value.
Check the investigation items of the alarm No. 1A.
PFU's internal resistor
regeneration transistor is
broken.
Unplug L+/L-, C+/C- and R1/R2
from the PFU unit, and measure the
resistance between L+/L- terminals.
If short-circuited, replace the power
backup unit.
51
Unable to cancel emergency stop. The
alarm 6C (Power supply: Main circuit
error) is occurring.
PFU's internal resistor
regeneration transistor is
broken.
Unplug L+/L-, C+/C- and R1/R2
from the PFU unit, and measure the
resistance between L+/L- terminals.
If short-circuited, replace the power
backup unit.
52 Power supply or drive unit fails to start.
An error in the control
power output circuit.
Check the investigation items of the alarm No. 52.
d1
Unable to cancel emergency stop.
External emergency stop is occurring
on the power supply unit. (The LED on
power supply unit shows "q".）
Over-regeneration
protection is working.
Check the investigation items of the warning No. D1.
d5
Unable to cancel emergency stop.
External emergency stop is occurring
on the power supply unit. (The LED on
power supply unit shows "q".）
An overheat was detected
by the thermal sensor of
the resistor unit.
Check the investigation items of the warning No. D5.