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Mitsubishi Electric FR-F720P-0.75K Instruction Manual Page 46

Fr-f700p series.
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(13) If the machine must not be restarted when power is restored after a power failure, provide a magnetic contactor
in the inverter's input side and also make up a sequence which will not switch on the start signal.
If the start signal (start switch) remains on after a power failure, the inverter will automatically restart as soon as the
power is restored.
(14) Inverter input side magnetic contactor (MC)
On the inverter input side, connect a MC for the following purposes. (Refer to page 4 for selection.)
1)To release the inverter from the power supply when a fault occurs or when the drive is not functioning (e.g. emergency
stop operation). For example, MC avoids 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.
2)To prevent any accident due to an automatic restart at restoration of power after an inverter stop made by a power
3)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-AC3 MC for the inverter input
side current when making an emergency stop during normal operation.
(15) Handling of 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 MC is provided for switching to the commercial power supply, for example, switch it ON/OFF after the
inverter and motor have stopped.
IPM motor is a synchronous motor with high-performance magnets embedded in the rotor. Motor terminals hold high-
voltage while the motor is running even after the inverter power is turned OFF. Before wiring or inspection, the motor
must be confirmed to be stopped. When the motor is driven by the load in applications such as fan and blower, a low-
voltage manual contactor must be connected at the inverter's output side, and wiring and inspection must be performed
while the contactor is open. Otherwise you may get an electric shock.
(16) Countermeasures against inverter-generated EMI
If electromagnetic noise generated from the inverter causes frequency setting signal to fluctuate and motor rotation
speed to be unstable when changing motor speed with analog signal, the following countermeasures are effective.
· Do not run the signal cables and power cables (inverter I/O cables) in parallel with each other and do not bundle them.
Run signal cables as far away as possible from power cables (inverter I/O cables).
Use shield cables as signal cables.
Install a ferrite core on the signal cable (Example: ZCAT3035-1330 TDK).
(17) Instructions for overload operation
When performing an operation of frequent start/stop of the inverter, increase/decrease in the temperature of the
transistor element of the inverter may repeat due to a continuous flow of large current, shortening the life from thermal
fatigue. Since thermal fatigue is related to the amount of current, the life can be increased by reducing bound current,
starting current, etc. Decreasing current may increase the life. However, decreasing current will result in insufficient
torque and the motor may not start. A counter action for this is to raise the permissible current level by increasing the
inverter capacity (up to 2 ranks) when using a general-purpose motor, and by increasing the inverter and IPM motor
capacities when using an IPM motor.
(18) Make sure that the specifications and rating match the system requirements.
Precautions for use of the inverter


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