Power-Off And Magnetic Contactor (Mc) - Mitsubishi Electric FR-A700 Series Instruction Manual

2.5 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 3 for selection.)
1) To release the inverter from the power supply when the inverter's protective function is activated or when the drive is
not functioning (e.g. emergency stop operation).
When cycle operation or heavy-duty operation is performed with an optional brake resistor connected, overheat and
burnout of the electrical-discharge resistor can be prevented if a regenerative brake transistor is damaged due to
insufficient heat capacity of the electrical-discharge resistor and excess regenerative brake duty.
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 reset the inverter for an extended period of time
The control power supply for inverter is always running and consumes a little power. When stopping the inverter for an
extended period of time, powering off the inverter will save power slightly.
4) To separate the inverter from the power supply to ensure safe maintenance and inspection work
The inverter's input side MC is used for the above purpose, select class JEM1038-AC3MC for the inverter input side
current when making an emergency stop during normal operation.
REMARKS
Since repeated inrush currents at power on will shorten the life of the converter circuit (switching life is about 1,000,000 times. (For
the 200V class 37K or more, switching life is about 500,000)), 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.
MCCB
Power
supply
Operation preparation
OFF ON
MC
MC
Start/Stop
MC
Operation
RA
Stop
RA
(2) Handling of the 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 to switch to a commercial power supply, for example, it is recommended to
use commercial power supply-inverter switchover operation Pr. 135 to Pr. 139 (
MC
U
R/L1
To the
V
S/L2
motor
W
T/L3
R1/L11
*2
S1/L21
T
*1
Inverter
C1
B1
A1
RA
STF(STR)
SD
Power-off and magnetic contactor (MC)
• Inverter start/stop circuit example
As shown on the left, always use the start signal (ON or
OFF across terminals STF or STR-SD) to make a start
or stop.
*1 When the power supply is 400V class, install a step-down
transformer.
*2 Connect the power supply terminals R1/L11, S1/L21 of the
control circuit to the primary 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-R1/L11 and S/L2-S1/L21. (Refer to page 18 for removal
of the jumper.)
Instruction Manual (applied)).
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