Checklist before starting operation
PRECAUTIONS FOR USE OF THE INVERTER
89
3
When using the electronic bypass
operation, electrical and
mechanical interlocks are provided
between the electronic bypass
contactors MC1 and MC2.
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 (SF-V5RU, SF-THY) nor with PM motors.)
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.
-
A countermeasure is provided for
power restoration after a power
failure.
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.
-
When using vector control, the
encoder is properly installed.
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.)
54
A magnetic contactor (MC) is
installed on the inverter's input
side.
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.
86
The magnetic contactor on the
inverter's output side is properly
handled.
Switch the magnetic contactor between the inverter and motor only when both
the inverter and motor are at a stop.
86
When using a PM motor, a low-
voltage manual contactor is
installed on the inverter's output
side.
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.
86
An EMI countermeasure is
provided for the frequency setting
signals.
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).
78
A countermeasure is provided for
an overload operation.
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.
-
The specifications and rating
match the system requirements.
Make sure that the specifications and rating match the system requirements. 128
Checkpoint Countermeasure
Refer
to page
Check
by user
Power
supply
Inverter
Undesirable current
MC2
MC1
Interlock
U
V
W
R/L1
S/L2
T/L3
IM
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