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E6581301
J-4
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 Molded Case 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.
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■ Magnetic contactor in the primary circuit
To detach the inverter from the power supply in any of the following cases, insert a magnetic contactor (primary-side
magnetic contactor) between the inverter and the power supply.
(1) If the motor overload relay is tripped
(2) If the protective detector (FL) built into the inverter is activated
(3) In the event of a power failure (for prevention of auto-restart)
(4) If the resistor protective relay is tripped when a braking resistor or braking resistor unit is used
When using the inverter with no magnetic contactor (MC) on the primary side, install a Molded Case Circuit Breaker
with a voltage tripping coil instead of an MC and adjust the Molded Case Circuit Breaker so that it will be tripped if the
protective relay referred to above is activated. To detect a power failure, use an undervoltage relay or the like.
Motor
IM
ST
F
CC
R/L1
U/T1
Stand by
Reverse
R
Forward
V/T2
W/T3
S/L2
T/L3
Power supply
MCCB
MC
Example of connection of a magnetic contactor in the primary circuit
Note 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).
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■ Magnetic contactor in the secondary circuit
A magnetic contactor may be installed on the secondary side to switch controlled motors or supply commercial power
to the load when the inverter is out of operation.
Note 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 current to
rush into the inverter which could lead to malfunction.
10.3 Installation of an overload relay
1) The VF-AS1 inverter has an electronic-thermal overload protective function.
In the following cases, however, an overload relay suitable for the adjustment of the motor electronic thermal
protection level (VJT) or appropriate to the motor used should be installed between the inverter and the motor.
• When using a motor with a current rating different to that of the corresponding Toshiba general-purpose motor
• When operating a single motor with an output smaller than that of the applicable standard motor.
When operating multiple motors at a time, be sure to install an overload relay for each individual motor.
2) When using the VF-AS1 inverter to operate a constant-torque motor, such as the Toshiba VF motor, adjust the
protection characteristic of the electronic thermal protection unit (NO) to the VF motor use.
3) It is recommended to use a motor with a thermal relay embedded in the motor coil to give sufficient protection to
the motor, especially when it runs in a low-speed range.