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.
To use an MC to perform an emergency stop during operation, select the MC by applying the inverter's input-side current
to the rated current specified in the JEM1038-AC-3 class.
• Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 500,000 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.
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.
When providing MCs to use the commercial power supply, switch the MCs after both the inverter and motor stop.
3. PRECAUTIONS FOR USE OF THE INVERTER
3.4 Power shutdown and magnetic contactor (MC)