Main circuit terminals
Power-off and magnetic contactor (MC)
(1) Inverter input side magnetic contactor (MC)
On the inverter's input side, it is recommended to provide an MC for the following
purposes. (Refer to page 10 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 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
The inverter's input side MC is used for the above purpose, select class JEM1038-
AC3 for the inverter input side current when making an emergency stop during
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.
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 29)
*1. When the power supply
is 400V class, install a
(2) Handling of output side magnetic contactor
In principle, do not provide a magnetic contactor between the inverter and motor and
switch it from off to on during operation. If it is switched on during inverter operation, a
large inrush current may flow, stopping the inverter due to overcurrent shut-off. When
an MC is provided for switching to the commercial power supply, for example, switch it
on/off after the inverter and motor have stopped.
Inverter Start/Stop Circuit Example