Inverter Capacity Selection; Starting Torque Of The Motor; Acceleration/Deceleration Times; Power Transfer Mechanism - Mitsubishi Electric FR-A700 Manual

Precautions for selection

Inverter capacity selection

When operating a special motor or more than one motor in parallel
with a single inverter, select the inverter capacity so that 1.1 times
the total rated motor current is less than the rated output current of
the inverter.

Starting torque of the motor

The start and acceleration characteristics of the motor driven by the
inverter are restricted by the overload current rating of that inverter.
Generally the torque characteristic is less than when the motor is
started by a commercial power supply. When torque boost
adjustment, advanced magnetic flux vector, real sensorless vector
or vector control cannot provide enough starting torque, select the
inverter of one rank higher capacity or increase the capacities of
both the motor and inverter.

Acceleration/deceleration times

The acceleration/deceleration time of the motor depends on the
motor-generated torque, load torque and load inertia moment
2
(GD ).
When the torque limit function or stall prevention function is
activated during acceleration/deceleration,
acceleration/deceleration time as the actual time may become
longer.
To decrease the acceleration/deceleration time, increase the torque
boost value (setting of a too large value may activate the stall
prevention function at a start, resulting in longer acceleration time), use
the advanced magnetic flux vector control or real sensorless vector
control, or increase the inverter and motor capacities. To decrease the
deceleration time, it is necessary to add the brake unit (FR-BU, MT-
BU5), power regeneration common converter (FR-CV), power
regeneration unit (MT-RC) or a similar device to absorb braking
energy.

Power transfer mechanism

(reduction gear, belt, chain, etc.)
When an oil-lubricated gear box, speed change/reduction gear or
similar device is used in the power transfer system, note that
continuous operation at low speed only may deteriorate oil
lubrication, causing seizure. When performing fast operation at
higher than 60Hz, fully note that such operation will cause strength
shortage due to the noise, life or centrifugal force of the power
transfer mechanism.
Instructions for overload operation
When performing operation of frequent start/stop of 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.
increase the life. However, decreasing current will result in
insufficient torque and the inverter may not start. Therefore, choose
the inverter which has enough allowance for current.
increase the
Decreasing current may
90