Precautions For Use Of The Inverter - Mitsubishi Electric FR-A720-0.4K Instruction Manual

3.5 Precautions for use of the inverter

The FR-A700 series is a highly reliable product, but using incorrect peripheral circuits or incorrect operation/handling
methods may shorten the product life or damage the product.
Before starting operation, always recheck the following items.
(1) Use crimping terminals with insulation sleeve to wire the power supply and motor.
(2) Application of power to the output terminals (U, V, W) of the inverter will damage the inverter. Never perform
such wiring.
(3) 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
an enclosure etc., take care not to allow chips and other foreign matter to enter the inverter.
(4) 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.
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Refer to page for the recommended cable sizes.
(5) The total wiring length should be within the prescribed length.
Especially for long distance wiring, the fast-response current limit function may decrease, or the equipment connected to
the secondary side may malfunction. This is caused by a charging current due to the stray capacity of the wiring. Therefore,
note the overall wiring length. (Refer to page 22.)
(6) Electromagnetic wave interference
The input/output (main circuit) of the inverter includes high frequency components, which may interfere with the
communication devices (such as AM radios) used near the inverter. In this case, set the noise filter valid to minimize
interference. (Refer to page 15)
(7) Do not install a power factor correction capacitor, surge suppressor or radio noise filter on the inverter output
side.
This will cause the inverter to trip or the capacitor, and surge suppressor to be damaged. If any of the above devices is
installed, immediately remove it.
(8) 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 not more than 30VDC
using a tester.
(9) 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 may damage
the inverter modules. These short circuits may be caused by peripheral circuit inadequacy, an earth (ground) fault
caused by wiring inadequacy, or reduced motor insulation resistance.
· Fully check the to-earth (ground) insulation and phase to phase insulation of the inverter output side before power-on.
Especially for an old motor or use in a hostile atmosphere, securely check the motor insulation resistance etc.
(10) 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. (For the 200V class 30K or higher, switching life is about 500,000)), 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.
(11) Across P/+ and PR terminals, connect only an external regenerative brake discharge resistor.
Do not connect a mechanical brake.
(12) 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 across terminals 10E and 5.

Precautions for use of the inverter

(Refer to page 61)
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