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Precautions for use of the inverter
(12) Provide electrical and mechanical interlocks for MC1 and MC2 which are used for 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 when the power supply is connected to the
inverter U, V, 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) Inverter input side magnetic contactor (MC)
On the inverter input side, provide MC for the following purposes. (Refer to page 4 for selection.)
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.
The inverter's input side MC is used for the above purpose, select class JEM1038-AC3 MC for the inverter
input side current when making an emergency stop during normal operation.
(15) 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.
(16) 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).
(17) Instructions for overload operation
When performing an operation of frequent start/stop of the inverter, increase/decrease in the temperature of the
transistor element of the inverter may 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
bound current, starting current, etc. Decreasing current may increase the life. However, decreasing current will
result in insufficient torque and the inverter may not start. Therefore, increase the inverter capacity to have enough
allowance for current.
(18) Make sure that the specifications and rating match the system requirements.
Power
supply
Inverter
Undesirable current
MC2
MC1
Interlock
U
V
W
R/L1
S/L2
T/L3
IM