Mitsubishi Electric FR-D700 Series Instruction Manual page 24

PRECAUTIONS FOR USE OF THE INVERTER
(10) 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
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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.
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Especially for an old motor or use in a hostile atmosphere, securely check the motor insulation resistance etc.
(11) 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. Turn ON/OFF the inverter start controlling terminals (STF,
STR) to run/stop the inverter. (
(12) Across terminals P/+ and PR, connect only an external brake resistor.
Do not connect a mechanical brake.
The brake resistor cannot be connected to the 0.1K and 0.2K. Do not connect anything to terminals P/+ and PR.
Also, never short between these terminals.
(13) 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 10 and 5.
(14) To use the commercial power supply, be sure to provide
electrical and mechanical interlocks between the electronic
bypass contactors MC1 and MC2.
When using a switching circuit as shown right, chattering due to
misconfigured sequence or arc generated at switching may
allow undesirable current to flow in and damage the inverter.
Miswiring may also damage the inverter.
(15) 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.
(16) Inverter input side magnetic contactor (MC)
On the inverter input side, connect a MC for the following purposes. (Refer to page 6 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.
Use the inverter input current as a reference for selection of an MC to perform an emergency stop during operation, and
select the MC conforming to JEM1038-AC-3 class rated operational current.
(17) 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.
(18) 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).
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Refer to the Instruction Manual (Applied))
Power
R/L1 U
supply
S/L2 V
T/L3 W
Inverter
MC1
Interlock
IM
MC2
Undesirable current