Mitsubishi Electric FR-F840-00023 Installation Manuallines page 32

PRECAUTIONS FOR USE OF THE INVERTER
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 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 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.
Inverter input side magnetic contactor (MC)
On the inverter input side, connect an MC for the following purposes. (Refer to the FR-F800 Instruction Manual.)
– To release the inverter from the power supply when a fault occurs or when the drive is not functioning (e.g. emergency
stop operation).
– To prevent any accident due to an automatic restart at restoration of power after an inverter stop made by a power
failure
– To separate the inverter from the power supply to ensure safe maintenance and inspection work.
If using an MC for emergency stop during operation, select an MC regarding the inverter input side current as JEM1038-
AC-3 class rated current.
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.
A PM motor is a synchronous motor with high-performance magnets embedded inside. High-voltage is generated at the
motor terminals while the motor is running even after the inverter power is turned OFF. Before wiring or inspection,
confirm that the motor is stopped. In an application, such as fan and blower, where the motor is driven by the load, a
low-voltage manual contactor must be connected at the inverter's output side, and wiring and inspection must be
performed while the contactor is open. Otherwise you may get an electric shock.
Countermeasures against inverter-generated EMI
When the motor speed is unstable, due to change in the frequency setting signal caused by electromagnetic noises
from the inverter, take the following measures when applying the motor speed by the analog signal:
– 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 shielded cables as signal cables.
– Install a ferrite core on the signal cable (Example: ZCAT3035-1330 TDK).
Make sure that the specifications and rating match the system requirements.
FR-F842 models only: Connect the converter unit and the inverter correctly. For details refer to the FR-CC2 Instruction
Manual.
26
R/L1 U
Power supply
S/L2 V
T/L3 W
Inverter
MC1
Interlock
IM
MC2
Undesirable current