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Checkpoint
When using the electronic bypass
operation, electrical and mechanical
interlocks are provided between the
electronic bypass contactors MC1
and MC2.
A countermeasure is provided for
power restoration after a power
failure.
When using the vector control, the
encoder is properly installed.
A magnetic contactor (MC) is
installed on the converter unit'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
When using a switching circuit as shown below, chattering due to mis-
configured sequence or arc generated at switching may allow undesirable
current to flow in and damage the inverter. Mis-wiring may also damage the
inverter.
(The commercial power supply operation is not available with vector control
dedicated motors nor with PM motors.)
Power
R/L1
supply
S/L2
T/L3
Inverter/
converter unit
If switching to the commercial power supply operation while a failure such as
an output short circuit has occurred between the magnetic contactor MC2 and
the motor, the damage may further spread. If a failure has occurred between
the MC2 and the motor, a protection circuit such as using the OH signal input
must be provided.
If the machine must not be restarted when power is restored after a power
failure, provide an MC in the converter 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 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 converter unit's input side, connect an MC for the following purposes:
• To disconnect the inverter and the converter unit 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 and the converter 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 converter unit input side current as JEM1038-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.
A PM motor is a synchronous motor with high-performance magnets
embedded inside. High-voltage is generated at the motor terminals while the
motor is running even after the inverter power is turned OFF. 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 and the converter unit
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 and converter 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 (inverter and
converter I/O cables).
• Use shielded cables.
• Install a ferrite core on the signal cable.
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 the inverter and the converter unit of a higher
capacity (up to two ranks). For a PM motor, use the inverter and the converter
unit, 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, built-in 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.
• Provide a common mode choke on the output side of the inverter.
• Turn OFF the EMC filter.
PRECAUTIONS FOR USE OF THE INVERTER
Checklist before starting operation
MC1
Interlock
U
IM
V
MC2
W
Undesirable current
Refer
Check
to
by user
page
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