Basically, select an inverter which fits the maximum applicable motor capacity of the selected motor.
After selecting an inverter, check if it meets both of the following conditions. If not, select an inverter
with one size larger in capacity and check again.
Rated motor current ≤ Rated output current of inverter
Max. continuous torque output time for application ≤ 1 min
Note 1. In the light load mode, the overload capacity of the inverter is 150% of the rated torque for 5 seconds.
Use the 5-seconds rating when determining the maximum continuous torque.
Note 2. If you want to use 0 Hz sensorless vector control, need a holding torque at a rotation speed of 0 (r/min),
or frequently require 150% of the rated torque or more, use an inverter with one size larger in capacity
than the one selected by the above method.
A-4-3
Overview of Braking Resistor Selection
Requirement of Braking Resistor
If the regenerative energy generated in deceleration or descent in an application is too large, the main
circuit voltage in the inverter may increase, which results in damage to the inverter.
Normally, the inverter has a built-in overvoltage protection function, which detects an overvoltage (0 V)
in the main circuit to prevent inverter damage. However
, because it detects a fault to stop the motor,
stable and continuous operation will be prevented.
Therefore, you need to use one or more braking resistors/regenerative braking units to absorb this re-
generative energy outside the inverter.
What is regenerative energy?
The load connected to a motor has kinetic energy when rotating, and potential energy when it is
subject to the gravity. When the motor decelerates, or when the load descends, the energy is fed
back to an inverter. This phenomenon is known as regeneration, and the energy is called regenera-
tive energy.
When decelerating, the motor serves
as a g
enerator to convert the kinetic/
potential energy into regenerative energy.
Kinetic energy
Potential energy
Load
Motor
Regenerative energy
Inverter
Preventing an overvoltage (0 V) in the main circuit without use of braking
resistors
The following are methods to prevent the occurrence of an overvoltage (0 V) in the main circuit
without connection of braking resistors.
Since these methods prolong the deceleration time, check that the selected method will not cause
application problems.
• Enable the overvoltage suppression function during deceleration
The overvoltage suppression function during deceleration is enabled by default.
Appendix
A-14
M1 Series Standard Type User's Manual (I669)
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