Mitsubishi Electric FR-E700 Instruction Manual page 94

Precautions for use of the inverter
● A short circuit or earth 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 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.
● Across P/+ and PR terminals, connect only an external brake resistor.
Do not connect a mechanical brake.
The brake resistor can not be connected to the FR-E720S-008SC and 015SC. Leave terminals + and
PR open. Also, never short between P/+ 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 commercial
power supply-inverter switch-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 error. Miswiring may
also damage the inverter.
Power
supply
CAUTION:
E
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.
4 - 2
M
3~
Undesirable current
Fig. 4-1:
Mechanical interlocks for MC1 and MC2
Operation
I001042E