Power Shutdown And Magnetic Contactor (Mc) - Mitsubishi Electric 800 Series Instruction Manual

3.4

Power shutdown and magnetic contactor (MC)

 Inverter input side magnetic contactor (MC)
On the inverter input side, it is recommended to provide an MC for the following purposes. (Refer to
• To disconnect the inverter from the power supply at activation of a protective function or at malfunctioning of the driving
system (emergency stop, etc.).
For example, an MC prevents 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.
• To prevent any accident due to an automatic restart at power restoration after an inverter stop made by a power failure.
• To separate the inverter from the power supply to ensure safe maintenance and inspection work.
Use the inverter input current as a reference for selection of an MC to perform an emergency stop during operation, and
select the MC conforming to JEM 1038-AC-3 class rated operational current.
NOTE
• 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 or OFF the start (STF/STR) signal for the
inverter start control to run or stop the inverter.
• Inverter start/stop circuit example
As shown in the following figure, always use the start signal (turn ON or OFF the STF/STR signal) to make a start or stop.
Operation preparation
OFF
ON
Start/Stop
MC
Start
Stop
RA
*1 When the power supply is 400 V class, install a stepdown transformer.
 Handling of the magnetic contactor on the inverter's output side
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.
 Handling of the manual contactor on the inverter's output side
A PM motor is a synchronous motor with high-performance magnets embedded inside. High-voltage is generated at the motor
terminals while the motor is running even after the inverter power is turned OFF. In an application where the PM motor is driven
by the load even after the inverter is powered OFF, a low-voltage manual contactor must be connected at the inverter's output
side.
100
3. Precautions for Use of the Inverter
3.4 Power shutdown and magnetic contactor (MC)
MCCB
MC
Power
supply
T ∗1
MC
MC
RA
RA
U
R/L1
To the
V
S/L2
motor
W
T/L3
Inverter
C
B
A
STF/STR
SD
page 25 for selection.)