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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 5 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 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.
(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.
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 magnetic contactor must be avoided. Turn ON/OFF the drive unit start controlling
terminals (STF, STR) to run/stop the drive unit.
Drive unit 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.
NOTE
A PM motor is a synchronous motor with embedded magnets. High-voltage is generated at motor terminals 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. For applications where the motor is driven by the load, the low-voltage manual contactor,
which is installed at the drive unit's output side, must be opened before wiring or inspection. Otherwise you may get
an electric shock.
Do not use a magnetic contactor at the drive unit's output side.
Three-phase AC
power supply
Drive unit
R/L1
S/L2
T/L3
U
V
W
Moto
r
MCCB MC
SD
STF(STR)
A
B
C
RA
OFF
ON
MC
Stop
Start
RA
MC
Operation preparation
Start/Stop
MC
RA