Mitsubishi Electric 800 Series Installation Manualline page 22

l 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 (Detailed).)
– To disconnect the inverter from the power supply at activation of a protective function or at malfunctioning of the driving
system (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.
l 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.
l Install a low voltage manual contactor on the inverter's output side when using a PM motor.
When a failure occurs between the MC2 and motor, make sure to provide a protection circuit, such as using the OH signal input.
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.
l 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 by TDK).
l Instructions for overload operation
When performing frequent starts/stops by the inverter, rise/fall in the temperature of the transistor element of the inverter will
repeat due to a repeated flow of large current, shortening the life from thermal fatigue. Since thermal fatigue is related to the
amount of current, the life can be increased by reducing current at locked condition, starting current, etc. Reducing current may
extend the service life but may also cause torque shortage, which leads to a start failure. Adding a margin to the current can
eliminate such a condition.
– For an induction motor, use an inverter of a higher capacity (up to two ranks).
– For a PM motor, use an inverter and PM motor of higher capacities.
l Make sure that the specifications and rating match the system requirements.
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