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10
10.2 Installation of a magnetic contactor
If using the inverter without installing a magnetic contactor (MC) in the primary circuit, use an MCCB (with a
power cutoff device) to open the primary circuit when the inverter protective circuit is activated.
If using a braking resistor or braking resistor unit, install a magnetic contactor (MC) or non-fuse circuit breaker
with a power cutoff device to the power supply of the inverter, so that the power circuit opens when the failure
detection relay (FL) in the inverter or the external overload relay is activated.
■ Magnetic contactor in the primary circuit
A magnetic contactor installed in the power supply circuit of the inverter cuts off the power supply to the cir-
cuit and prevents the inverter from restarting in case of a power failure, a trip of the overload relay (Th-Ry)
or the activation of the inverter protective circuit.
In addition, if the FL contact of the failure detection relay in the VF-S9 is connected to the operation circuit
of the magnetic contactor on the primary side, the magnetic contactor (MC) will be tripped when the inverter
protective circuit is activated.
MC
MC
IM
VF-S9
R/L1 U/T1
W/T2
W/T3
F
R
CC
S/L2
T/L3
FLC
FLB
FLA
MCCB
Power supply
Motor
Thermal relay
Forward run
Reverse run
Surge killer
Example of connection of a magnetic contactor in the primary circuit
Notes on wiring
• When frequently switching between start and stop, do not use the magnetic contactor on the primary side as
an on-off switch for the inverter. Instead, stop and start the inverter by using terminals F and CC (forward run)
or R and CC (reverse run).
• Be sure to attach a surge killer to the exciting coil of the magnetic contactor (MC).
■ Magnetic contactor in the secondary circuit
A magnetic contactor may be installed on the secondary side to switch controlled motors or supply com-
mercial power to the load when the inverter is out of operation.
Notes on wiring
• Be sure to interlock the magnetic contactor on the secondary side with the power supply to prevent commercial
power from being applied to the inverter output terminals.
• When installing a magnetic contactor (MC) between the inverter and the motor, avoid turning the magnetic
contactor on or off during operation. Turning the magnetic contactor on or off during operation causes a cur-
rent to rush into the inverter which could lead to malfunction.