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3. PRECAUTIONS FOR USE OF THE CONVERTER UNIT
3.3 Power shutdown and magnetic contactor (MC)
3.3
Power shutdown and magnetic contactor (MC)
Converter unit input side magnetic contactor (MC)
On the converter unit input side, it is recommended to provide an MC for the following purposes.
(Refer to
for selection.)
• To disconnect the inverter from the power supply at activation of a protective function or at malfunctioning of the driving
system (emergency stop, etc.).
• To prevent any accident due to an automatic restart at power restoration after an inverter stop made by a power failure.
• To separate the inverter from the power supply to ensure safe maintenance and inspection work.
NOTE
• Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 1,000,000 times),
frequent starts and stops of the magnetic contactor must be avoided. Turn ON or OFF the start (STF/STR) signal for the
inverter start control to run or stop the inverter.
• Inverter start/stop circuit example
As shown in the following figure, always use the start signal (turn ON or OFF the STF/STR signal) to make a start or stop.
*1
Install a stepdown transformer.
*2
Connect the power supply terminals R1/L11, S1/L21 of the control circuit to the input side of the MC to hold an alarm signal when the inverter's
protective circuit is activated. At this time, remove the jumpers connected to terminals R1/L11 and S1/L21. (Refer to
for removal of the
jumper.)
Handling of the magnetic contactor on the inverter's output side
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 the commercial power
supply-inverter switchover function
Pr.135 to Pr.139
.
P/+
N/-
P/+
N/-
A1
B1
C1
RDA
MC
R/L1
S/L2
T/L3
R1/L11
S1/L21
OFF
ON
MC
RA
MC
RA
MC
RA
U
V
A1
B1
C1
W
SD
STF/STR
R1/L11
S1/L21
X10
SE
SD
T
Power
supply
MCCB
Converter
unit
Stop
Start
Operation preparation
Start/Stop
To the
motor
Inverter
∗1
∗2
∗2
