Precautions For Use Of The Inverter - Mitsubishi Electric 800 Series Installation Manualline

4 PRECAUTIONS FOR USE OF THE INVERTER

The FR-F800 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:
l Use crimping terminals with insulation sleeve to wire the power supply and motor.
l Application of power to the output terminals (U, V, W) of the inverter will damage the inverter. Never perform such wiring.
l 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.
l Use cables of the appropriate size to make a voltage drop of 2% maximum.
If the wiring distance is long between the inverter and motor, a voltage drop in the main circuit will cause the motor torque to
decrease especially at the output of a low frequency.
Refer to page 7 for the recommended cable size.
l Keep the total wiring length within the specified length.
In long distance wiring, charging currents due to stray capacitance in the wiring may degrade the fast-response current limit
operation or cause the equipment on the inverter's output side to malfunction. Pay attention to the total wiring length. (Refer to
page 8.)
l 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, activate the EMC filter (turn ON the EMC filter
ON/OFF connector) to minimize interference. (Refer to the FR-F800 Instruction Manual (Detailed).)
l Electrical corrosion of the bearing
When a motor is driven by the inverter, axial voltage is generated on the motor shaft, which may cause electrical corrosion of
the bearing in rare cases depending on the wiring, load, operating conditions of the motor or specific inverter settings (e.g. high
carrier frequencies).
Contact your sales representative to take appropriate countermeasures for the motor.
The following shows examples of countermeasures for the inverter:
– Decrease the carrier frequency.
– Consider the use of a sine wave output filter.
l 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.
l Before starting wiring or other work after the inverter is operated, wait for at least 10 minutes after the power supply turns OFF,
then confirm that the voltage across the main circuit terminals P/+ and N/- of the inverter is low enough using a tester, etc. The
capacitor is charged with high voltage for some time after power off and it is dangerous.
l A short circuit or earth fault on the inverter output side may damage the inverter module.
– Fully check the insulation resistance of the circuit prior to inverter operation since repeated short circuits caused by
peripheral circuit inadequacy or an earth fault caused by wiring inadequacy or reduced motor insulation resistance may
damage the inverter module.
– Fully check the to-earth (ground) 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.
l Do not use the inverter input side magnetic contactor (MC) 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.
l 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 10E and 5.
l Provide electrical and mechanical interlocks for MC1 and MC2
which are used for commercial power supply-inverter switch-
over.
When the wiring is incorrect or if there is a switching circuit as
shown on the right, 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 error.
(The commercial power supply operation is not available 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.
l Provide a countermeasure for power restoration after a power failure.
If the machine must not be restarted when power is restored after a power failure, provide a magnetic contactor (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.
R/L1 U
Power supply
S/L2 V
T/L3 W
Inverter
MC1
Interlock
IM
MC2
Undesirable current
15