Power shutdown and magnetic contactor (MC)
Converter unit input side magnetic contactor (MC)
On the converter unit input side, it is recommended to provide an MC for the following purposes.
• To disconnect the inverter from the power supply at activation of a protective function or at malfunctioning of the driving
system (emergency stop, etc.).
• 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 conforming to JEM 1038-AC-3 rated current for
the converter unit rated input current.
• Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 1,000,000 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.
To hold the Fault signal when the inverter's protective circuit is activated, connect the control circuit power supply terminals R1/L11 and S1/L21
to the input side of the MC. At this time, remove the jumpers connected to terminals R1/L11 and S1/L21. (Refer to
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 an MC is provided to switch to a commercial power supply, for example, it is recommended to use the electronic bypass
function Pr.135 to Pr.139. (The commercial power supply operation is not available with Vector control dedicated motors 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
3. PRECAUTIONS FOR USE OF THE INVERTER
3.4 Power shutdown and magnetic contactor (MC)
55for removal of the