Mitsubishi Electric FR-A520-0.4K Instruction Manual page 54

(3) Power-off and magnetic contactor (MC)
On the inverter primary side, it is recommended to provide an MC for the following purposes (Refer to page
46 for selection.):
1)To release the inverter from the power supply when the inverter protective function is activated or the drive
becomes faulty (e.g. emergency stop operation).
When cycle operation or heavy-duty operation is performed with an optional brake resistor connected,
overheat and burnout of the electrical-discharge resistor can be prevented if a regenerative brake
transistor is damaged due to insufficient heat capacity of the electrical-discharge resistor and excess
regenerative brake duty.
2)To prevent an accident due to an automatic restart made at power restoration after an inverter stop made
by a power failure.
3)To rest the inverter for an extended period of time.
The control power supply for inverter is always running and consumes a little power. When stopping the
inverter for an extended period of time, powering off the inverter will save power slightly.
4)To separate the inverter from the power supply to ensure safe maintenance and inspection work.
As the inverter's primary MC is used for the above purposes, select the one of class JEM1038-AC3 for the
inverter input side current when making an emergency stop during normal operation.
Note: The MC may be switched on/off to start/stop the inverter. However, since reapeated inrush
currents at power-on will shorten the life of the converter circuit (swithing life is about 100,000
times), frequent starts and stops must be avoided. Turn on/off the inverter start controlling
terminals (STF, STR) to run/stop the inverter.
•
Circuit example of start/stop of the inverter.
As shown on the right, always use the start
signal (ON or OFF across terminals STF or
STR-SD) to make a start or stop. (Refer to
page 13.)
REMARKS
*1. For the 400V class power supply, install a voltage-reducing transformer.
*2. Connect the power supply terminals R1 and S1 to the primary side of the MC to hold an alarm signal when the inverter's
protective circuit is activated. At this time, remove jumpers across terminals R-R1 and S-S1. (For removal of jumpers, refer
to page 20)
Power
supply
Operation ready
ON
OFF
MC
Start/Stop
Operation
MC
RA
OFF
45
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INSTALLATION AND WIRING
NFB
MC
R
S
T
R1
*2
S1
T *1
Inverter
MC
RA
STF(STR)
SD
RA
2
U
V
To motor
W
A
B
C