Precautions for use of the inverter
● Do not use the inverter input side magnetic contactor to start/stop the inverter.
Always use the start signal (ON/OFF of STF and STR signals) to start/stop the inverter.
● Across + and PR terminals, connect only an external regenerative brake discharging resistor.
Do not connect a mechanical brake.
The brake resistor can not be connected to the FR-E720S-008 and 015. Leave terminals +
and PR open. Also, never short between + and PR.
● Do not apply a voltage higher than the permissible voltage to the inverter I/O signal circuits.
Contact to the inverter I/O signal circuits or opposite polarity may damage the I/O devices.
Especially check the wiring to prevent the speed setting potentiometer from being connected
incorrectly to short terminals 10-5.
● Provide electrical and mechanical interlocks for MC1 and MC2 which are used for commer-
cial power supply-inverterswitch-over.
When the wiring is incorrect or if there is a commercial power supply-inverter switch-over
circuit as shown below, the inverter will be damaged by leakage current from the power
supply due to arcs generated at the time of switch-over or chattering caused by a sequence
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.
● Instructions for overload operation
When performing 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 insuffi-
cient torque and the inverter may not start. Therefore, increase the inverter capacity to have
enough allowance for current.
● Make sure that the specifications and rating match the system requirements.
● When the motor speed is unstable, due to change in the frequency setting signal caused by
electromagnetic noises from the inverter, take the following measures when applying the
motor speed by the analog signal.
– 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).
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Mechanical interlocks for MC1 and MC2