Mitsubishi Electric FR-D720-0.2K-G Instruction Manual page 57

Precautions for use of the drive unit
(11) Do not use the drive unit input side magnetic contactor to start/stop the drive unit.
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 MC must be avoided. Turn ON/OFF the drive unit start controlling terminals (STF,
STR) to run/stop the drive unit. (Refer to page 44)
(12) Across terminals P/+ and PR, connect only an external brake resistor.
Do not connect a mechanical brake.

The brake resistor cannot be connected to the 0.2K. Do not connect anything to terminals P/+ and PR.

Also, never short between these terminals.
(13) Do not apply a voltage higher than the permissible voltage to the drive unit I/O signal circuits.
Application of a voltage higher than the permissible voltage to the drive unit I/O signal circuits or opposite polarity may
damage the I/O devices. Especially check the wiring to prevent the speed setting potentiometer from being connected
incorrectly to short terminals 10 and 5.
(14) If the machine must not be restarted when power is restored after a power failure, provide a magnetic contactor
in the drive unit'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 drive unit will automatically restart as soon as the
power is restored.
(15) Drive unit input side magnetic contactor (MC)
On the drive unit input side, connect a MC for the following purposes. (Refer to page 4 for selection.)
1)To release the drive unit 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 a drive unit stop made by a power
failure
3)To separate the drive unit from the power supply to ensure safe maintenance and inspection work.
If using an MC for emergency stop during operation, select an MC regarding the drive unit input side current as
JEM1038-AC-3 class rated current.
(16) Handling of drive unit output side magnetic contactor
Switch the magnetic contactor between the drive unit and motor only when both the drive unit and motor are at a stop.
When the magnetic contactor is turned ON while the drive unit is operating, overcurrent protection of the drive unit and
such will activate.
(17) Countermeasures against drive unit-generated EMI
If electromagnetic noise generated from the drive unit causes speed 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 (drive unit I/O cables) in parallel with each other and do not bundle
them.
 Run signal cables as far away as possible from power cables (drive unit I/O cables).
 Use shield cables as signal cables.
 Install a ferrite core on the signal cable (Example: ZCAT3035-1330 TDK).
(18) Instructions for overload operation
When performing operation of frequent start/stop of the drive unit, rise/fall in the temperature of the transistor element of
the drive unit will repeat due to a repeated 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 current at locked condition, starting
current, etc. Decreasing current may increase the life. However, decreasing current will result in insufficient torque and
the drive unit may not start. Reducing the current may extend the service life but may also cause torque shortage, which
leads to a start failure. An effective measure is to use a drive unit and motor with higher capacities. Doing so will provide
a margin to the load.
(19) Make sure that the specifications and rating match the system requirements.
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