Mitsubishi Electric 700 Series Installation Manualline page 19

PRECAUTIONS FOR USE OF THE INVERTER
A motor with encoder is necessary for vector control. In addition, connect the encoder directly to the backlash-free motor
shaft. (An encoder is not necessary for real sensorless vector control.)
Inverter input side magnetic contactor (MC)
On the inverter input side, connect a MC for the following purposes. (Refer to Chapter 1 of the Instruction Manual
(Applied).)
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.
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.
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).
Instructions for overload operation
When performing operation of frequent start/stop of the inverter, increase/decrease in the temperature of the transistor
element of the inverter may repeat due to a continuous 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 bound current, starting
current, etc. Decreasing current may increase the life. However, decreasing current will result in insufficient torque and
the inverter may not start. Therefore, increase the inverter capacity to have enough allowance for current (up to 2 rank
larger in capacity).
Make sure that the specifications and rating match the system requirements.
14