Mitsubishi Electric FR-A806 Instruction Manual page 90

Checkpoint
A countermeasure is provided for
power restoration after a power failure.
When using vector control, the
encoder is properly installed.
A magnetic contactor (MC) is installed
on the inverter's input side.
The magnetic contactor on the
inverter's output side is properly
handled.
When using a PM motor, a low-voltage
manual contactor is installed on the
inverter's output side.
An EMI countermeasure is provided
for the frequency setting signals.
A countermeasure is provided for an
overload operation.
The specifications and rating match
the system requirements.
Countermeasures are taken against
electrical corrosion on the motor
bearing.
Countermeasure
If the machine must not be restarted when power is restored after a power
failure, provide an MC 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.
The encoder must be directly connected to a motor shaft without any
backlash. (Real sensorless vector control, PM sensorless vector control do not
require an encoder.)
On the inverter's input side, connect 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.
If using an MC for emergency stop during motor driving, select an MC
regarding the inverter input side current as JEM 1038-AC-3 class rated
current.
Switch the magnetic contactor between the inverter and motor only when both
the inverter and motor are at a stop.
When a failure occurs between the MC2 and motor, make sure to provide a
protection circuit, such as using the OH signal input.
In an application, such as fan and blower, where the motor is driven by the
load, 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.
If electromagnetic noise generated from the inverter causes frequency setting
signal to fluctuate and the motor rotation speed to be unstable when changing
the motor speed with analog signals, 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 shielded cables.
• Install a ferrite core on the signal cable (Example: ZCAT3035-1330 by TDK).
When performing frequent starts/stops by the inverter, rise/fall in the
temperature of the transistor element of the inverter 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. Reducing current
may extend the service life but may also cause torque shortage, which leads
to a start failure. Adding a margin to the current can eliminate such a condition.
For an induction motor, use an inverter of a higher capacity (up to two ranks).
For a PM motor, use an inverter and PM motor of higher capacities.
Make sure that the specifications and rating match the system requirements.
When a motor is driven by the inverter, axial voltage is generated on the motor
bearing, which may cause electrical corrosion of the bearing in rare cases
depending on: condition of the grease used for the bearing, wiring, load,
operating conditions of the motor, or specific inverter settings (high carrier
frequency, EMC filter ON).
Contact your sales representative to take appropriate countermeasures for the
motor.
The following shows examples of countermeasures for the inverter.
• Decrease the carrier frequency.
• Turn OFF the EMC filter.
• Provide a common mode choke
effective regardless of the EMC filter ON/OFF connector setting.)

Recommended common mode choke: FT-3KM F series FINEMET
common mode choke cores manufactured by Hitachi Metals, Ltd.
FINEMET is a registered trademark of Hitachi Metals, Ltd.
PRECAUTIONS FOR USE OF THE INVERTER
Checklist before starting operation
on the output side of the inverter. (This is

Refer Check
to by
page user
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