41
Power-off and magnetic contactor (MC)
3
3.2 Power-off and magnetic contactor (MC)
(1) Inverter input side magnetic contactor (MC)
On the inverter input side, it is recommended to provide an MC for the following purposes.
(
Refer to
page 3
for selection.)
1) To release the inverter from the power supply when the fault occurs or when the drive is not functioning (e.g.
emergency stop operation).
2) To prevent any accident due to an automatic restart at restoration of power after an inverter stop made by a power failure
3) To reset 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
The inverter's input side MC is used for the above purpose, select class JEM1038-AC3MC for the inverter input side
current when making an emergency stop during normal operation.
(2) Handling of the inverter output side magnetic contactor
Switch the magnetic contactor between the inverter and motor only when both the inverter and motor are at a stop.
When the magnetic contactor is turned on while the inverter is operating, overcurrent protection of the inverter and
such will activate. When an MC is provided to switch to a commercial power supply, for example, it is recommended to
use bypass-inverter switchover function
Pr. 135 to Pr. 139 (
chapter 4 of
the instruction manual (applied))
.
REMARKS
Since repeated inrush currents at power on will shorten the life of the converter circuit (switching life is about 500,000 times.),
frequent starts and stops of the MC must be avoided. Turn on/off the inverter start controlling terminals (STF, STR) to run/stop the
inverter.
• Inverter start/stop circuit example
As shown on the left, always use the start signal (ON or
OFF across terminals STF or STR-SD) to make a start
or stop.
*1 When the power supply is 400V class, install a step-down
transformer.
*2 Connect the power supply terminals R1/L11, S1/L21 of the
control circuit 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/
L1-R1/L11 and S/L2-S1/L21. (Refer to
for removal
of the jumper.)
Power
supply
MCCB
RA
U
V
A1
B1
C1
W
To the
motor
Inverter
MC
STF(STR)
R/L1
S/L2
T/L3
R1/L11
S1/L21
OFF
ON
MC
Stop
Operation
RA
MC
Operation preparation
Start/Stop
RA
MC
SD
T
*1
*2
Summary of Contents for FR-A741-11K
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