Mitsubishi Electric FR-A700 Series Installation Manuallines page 19

(12) Provide electrical and mechanical interlocks for MC1 and
MC2 which are used for electronic bypass operation.
When the wiring is incorrect or if there is an electronic
bypass circuit as shown on the right, the inverter will be
damaged by leakage current from the power supply when
it is connected to the inverter U, V, and W terminals due to
arcs generated at the time of switch-over or chattering
caused by a sequence error.
(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) A motor with encoder is necessary for vector control. In addition, connect the encoder directly to the backlash-
free motor shaft. (An encoder is not necessary for Real sensorless vector control.)
(15) Inverter input side magnetic contactor (MC)
On the inverter input side, connect a MC for the following purposes. (Refer to Chapter 1 of the Instruction Manual (Applied).)
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
failure
3)To separate the inverter 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 inverter input side current as JEM1038-
AC-3 class rated current.
(16) 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.
(17) 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).
(18) Instructions for overload operation
When performing an operation of frequent start/stop with the inverter, rise/fall in the temperature of the transistor element
of the inverter will 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 current at locked condition, starting
current, etc. Decreasing current may increase the life. However, decreasing current will result in insufficient torque and
the inverter may not start. Therefore, choose the inverter which has enough allowance for current (up to 2 rank larger in
capacity).
(19) Make sure that the specifications and rating match the system requirements.
PRECAUTIONS FOR USE OF
Power supply
R/L1
S/L2
T/L3 W
Inverter
THE INVERTER
MC1
Interlock
U
IM
V
MC2
Undesirable current
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