Power-Off And Magnetic Contactor (Mc) - Mitsubishi Electric FR-A720-0.4K Instruction Manual

3.3 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 4 for selection.)
1) To release the inverter from the power supply when a fault occurs or when the drive is not functioning (e.g.
emergency stop operation). For example, MC avoids overheat or burnout of the brake resistor when heat capacity of
the resistor is insufficient or brake regenerative transistor is damaged with short while connecting an optional brake
resistor.
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 separate the inverter from the power supply to ensure safe maintenance and inspection work
If using an MC for emergency stop during operation, select an MC regarding the inverter input side current as
JEM1038-AC-3 class rated current.
REMARKS
Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 1,000,000 times.
(For the 200V class 30K or higher, switching life is about 500,000)), 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.
MCCB
Power
supply
Operation preparation
MC
OFF ON
MC
Start/Stop
RA
MC
Start
Stop
RA
(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 operation Pr. 135 to Pr. 139 (Refer to page 369).
MC
U
R/L1
To the
V
S/L2
motor
W
T/L3
R1/L11
*2
S1/L21
T
*1
Inverter
C1
B1
A1
RA
STF/STR
SD

Power-off and magnetic contactor (MC)

• Inverter start/stop circuit example
As shown on the left, always use the start signal (ON or
OFF of STF (STR) signal) to make a start or stop. (Refer
to page 236)
*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 and R1/L11 and S/L2 and S1/L21. (Refer to page 23 for
removal of the jumper.)
3
61