Mitsubishi Electric FR-A820-00046 Instruction Manual page 140

Power-OFF and magnetic contactor (MC)
Example Inverter start/stop circuit example
As shown below, always use the start signal (ON or OFF of STF(STR) signal) to make a start or stop.
Fig. 3-12:
When the power supply is 400 V class, install a stepdown transformer.
Connect the power supply terminals R1/L11, S1/L21 of the control circuit to the input 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 2-48 for removal of
the jumper.)
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 mo-
tor are at a stop. When the magnetic contactor is turned ON while the inverter is operating, overcur-
rent protection of the inverter and such will activate. When an MC is provided to switch to a commer-
cial power supply, for example, it is recommended to use the electronic bypass function Pr. 35 to Pr.
139 (refer to page 5-471). (The commercial power supply operation is not available with vector control
dedicated motors (SF-V5RU, SF-THY) nor with PM motors.)
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.
NOTES Before wiring or inspection for a PM motor, confirm that the PM motor is stopped. In an applica-
tion, such as fan and blower, where the motor is driven by the load, a low-voltage manual contac-
tor must be connected at the inverter's output side, and wiring and inspection must be performed
while the contactor is open. Otherwise you may get an electric shock.
Do not open or close the contactor while the inverter is running (outputting).
3 - 18
Power
supply
Operation preparation
OFF ON
MC
Start-/Stop
MC Start
Stop
RA
Start and stop of the inverter
Precautions for use of the inverter
MCCB
MC
R/L1
S/L2
T/L3
R1/L11
S1/L21
T
Inverter
MC
RA
STF/STR
SD
RA
U
To the
V
motor
W
C1
B1
A1
I002424E