Mitsubishi Electric FR-A820-00046 Instruction Manual page 144

Checklist before starting operation
Checkpoint
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.
Tab. 3-14:
3 - 22
Countermeasure
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.
Checklist before starting operation (3)
Precautions for use of the inverter
Refer
to
page
3-17
3-6
⎯
8-1
Check
by user