MGI M4000E series, Instruction Manual

Page: 53 / 215

42
INSTALLATION AND WIRING
2.3.6 Power off and magnetic contactor (MC)
(1) Inverter primary side magnetic contactor (MC)
On the inverter primary side, it is recommended to provide an MC for the following
purposes. (Refer to page 41 for selection.)
1)
To release the inverter from the power supply when the inverter protective function
is activated or the drive becomes faulty (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 rest 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 a long time, switching inverter power off
saves power slightly.
4) To separate the inverter from the power supply to ensure safe maintenance and
inspection work
As the inverter's primary MC is used for the above purposes, select the one of
class JEM1038-AC3 for the inverter input side current when making an emergency
stop during normal operation.
(2) Handling of secondary side magnetic contactor
Note that if it is switched off then on again during operation when the magnetic
contactor is installed between the inverter and motor, a large inrush current may flow,
affecting the motor.
REMARKS
The MC may be switched on/off to start/stop the inverter. However, since repeated
inrush currents at power-on will shorten the life of the converter circuit (switching life is
about 100,000 times), frequent starts and stops must be avoided.
Turn on/off the inverter start controlling terminals (STF, STR) to run/stop the inverter.
Inverter Start/Stop Circuit
Example
As shown on the right, always
use the start signal (ON or OFF
across terminals STF or STR-
SD) to make a start or stop.
(Refer to page 18.)
REMARKS
*1 Install a step-down
transformer.
MCCB
OFF
ON
MC
MC
RA
U
V
W
SD
MC
STF(STR)
RA
RA
MC
T (*1)
A
B
C
Power
supply
To
motor
Inverter
Start/Stop
OFF
Operation
Operation ready
R
S
T
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