Power-Off And Magnetic Contactor (Mc) - Mitsubishi Electric FR-D720-0.2K-G Instruction Manual

Power-OFF and magnetic contactor (MC)

3.3

Power-OFF and magnetic contactor (MC)

(1) Drive unit input side magnetic contactor (MC)
On the drive unit input side, it is recommended to provide an MC for the following purposes.
(Refer to page 4 for selection.)
1) To release the drive unit 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 a drive unit stop made by a power failure
3) To separate the drive unit 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 drive unit 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 drive unit start controlling terminals (STF, STR)
to run/stop the drive unit.
Three-phase AC
power supply
Operation preparation
MC
OFF
ON
MC
Start/Stop
RA
MC
Start
Stop
RA
(2) Handling of drive unit output side magnetic contactor
Switch the magnetic contactor between the drive unit and motor only when both the drive unit and motor are at a stop. When
the magnetic contactor is turned ON while the drive unit is operating, overcurrent protection of the drive unit and such will
activate.
NOTE
 A PM motor is a synchronous motor with magnets embedded. Motor terminals hold high-voltage while the motor is
running even after the drive unit power is turned OFF. Before wiring or inspection, the motor must be confirmed to be
stopped. When the motor is driven by the load in applications, a low-voltage manual contactor must be connected at
the drive unit's output side, and wiring and inspection must be performed while the contactor is open. Otherwise you
may get an electric shock.
44
Drive unit
MCCB MC
R/L1
S/L2
T/L3
T
*1
RA
STF(STR)
SD
 Drive unit start/stop circuit example
As shown on the left, always use the start signal
U
V Motor
(ON or OFF of STF(STR) signal) to make a start
W
or stop.

When the power supply is 400V class, install a step-down
C
transformer.
B
A