Power-Off And Magnetic Contactor (Mc) - Mitsubishi Electric FR-D720-0.4K Instruction Manual

Power-OFF and magnetic contactor (MC)

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 the 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.),
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.
Three-phase AC
power supply
Operation preparation
OFF ON MC
MC
Start/Stop
RA
Start
MC
Stop
RA
(2) Handling of 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 for switching to the commercial power supply, for example, switch it ON/OFF after the inverter and
motor have stopped.
46
Inverter
MCCB MC
R/L1
S/L2
T/L3
T
*1
RA
STF(STR)
SD
Inverter start/stop circuit example
As shown on the left, always use the start signal
U
Motor
V
(ON or OFF of STF(STR) signal) to make a start
W
or stop.
∗1
When the power supply is 400V class, install a step-down
C
transformer.
B
A