Precautions For The Use Of The Inverter - Mitsubishi Electric 700 Series Installation Manualline

4 PRECAUTIONS FOR USE OF THE INVERTER
The FR-A700 series is a highly reliable product, but incorrect peripheral circuit making or operation/handling method may
shorten the product life or damage the product.
Before starting operation, always recheck the following items.
Use crimping terminals with insulation sleeve to wire the power supply and motor.
Application of power to the output terminals (U, V, W) of the inverter will damage the inverter. Never perform such wiring.
After wiring, wire offcuts must not be left in the inverter.
Wire offcuts can cause an alarm, failure or malfunction. Always keep the inverter clean. When drilling mounting holes in
a control box etc., take care not to allow chips and other foreign matter to enter the inverter.
Use cables of the size to make a voltage drop 2% maximum.
If the wiring distance is long between the inverter and motor, a main circuit cable voltage drop will cause the motor
torque to decrease especially at the output of a low frequency.
Refer to page 8 for the recommended cable size.
The overall wiring length should be 500m maximum.
Especially for long distance wiring, the fast-response current limit function may be reduced or the equipment connected
to the inverter output side may malfunction or become faulty under the influence of a charging current due to the stray
capacity of the wiring. Therefore, note the overall wiring length. (Refer to page 8)
Electromagnetic Compatibility
Operation of the frequency inverter can cause electromagnetic interference in the input and output that can be
propagated by cable (via the power input lines), by wireless radiation to nearby equipment (e.g. AM radios) or via data
and signal lines. Install an optional filter if present to reduce air propagated interference on the input side of the inverter.
Use AC or DC reactors to reduce line propagated noise (harmonics). Use shielded motor power lines to reduce output
noise.
Do not install a power factor correction capacitor, varistor or arrester on the inverter output side.
This will cause the inverter to trip or the capacitor, varistor, or arrester to be damaged. If any of the above devices is
installed, immediately remove it.
For some short time after the power is switched OFF, a high voltage remains in the smoothing capacitor.
When accessing the inverter for inspection, wait for at least 10 minutes after the power supply has been switched OFF,
and then make sure that the voltage across the main circuit terminals P/+ and N/- of the inverter is no more than 30VDC
using a tester.
A short circuit or earth (ground) fault on the inverter output side may damage the inverter modules.
– Fully check the insulation resistance of the circuit prior to inverter operation since repeated short circuits caused by
peripheral circuit inadequacy or an earth (ground) fault caused by wiring inadequacy or reduced motor insulation
resistance may damage the inverter modules.
– Fully check the to-earth insulation and inter-phase insulation of the inverter output side before power-on.
Especially for an old motor or use in hostile atmosphere, securely check the motor insulation resistance etc.
Do not use the inverter input side magnetic contactor to start/stop the inverter.
Since repeated inrush currents at power ON will shorten the life of the converter circuit (switching life is about 1,000,000
times), frequent starts and stops of the MC must be avoided. Always use the start signal (ON/OFF of STF and STR
signals) to start/stop the inverter.
Do not apply a voltage higher than the permissible voltage to the inverter I/O signal circuits.
Application of a voltage higher than the permissible voltage 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 10E or 5.
Provide electrical and mechanical interlocks for MC1 and
MC2 which are used for bypass operation.
When the wiring is incorrect or if there is a bypass circuit as
shown below, the inverter will be damaged by leakage
current from the power supply when it is connected to the
inverter U, V, and W terminals due to arcs generated at the
time of switch-over or chattering caused by a sequence
error.
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.
Power supply
Inverter
MC1 Interlock
M
3~
MC2
Undesirable current
13