A load connected to a motor has kinetic energy when rotating, and potential energy when it is located in a high position. When the motor decelerates, or when the load descends, this energy is returned to an inverter. This is known as regeneration, and the energy generated is known as regenerative energy.

Applications Requiring Braking Resistors

In applications where excessive regenerative motor energy is produced during deceleration or descent, the main-circuit voltage in the Inverter may rise high enough to damage the Inverter. Standard Inverters, which are equipped with the overvoltage protection function, detect the overvoltage protection and stop operation, which will prevents any damage.

Although the Inverter will be protected, the overvoltage protection function will generate an error and the motor will stop; this system configuration will not provide stable continuous operation. This regenerative energy needs to be emitted to the outside of the Inverter using the braking resistor or regenerative braking unit.

Avoiding the Use of a Braking Resistor

The following methods can be used to avoid having to connect a Braking Resistor. These methods require the deceleration time to be extended, so you must evaluate whether extending the deceleration time will cause any problems in the application.

– Enable the “stall prevention during deceleration” function; the default setting for this function is enabled. (Increase the deceleration time automatically so as not to generate the overvoltage protection.)

– Set a longer deceleration time. (This reduces the rate at which the regenerative energy is produced.)

– Select “coast to stop” as the stopping method. (Regenerative energy will not be returned to the Inverter.)

Make a Simple Selection for Braking Resistors

It can be a simple selecting method by using the ratio of time in which regenerative energy is produced in a normal operating pattern.

Calculate the usage ratio from the following operating pattern.

Calculate the usage ratio from the following operating pattern.

Go to Omron selection guide

See the range of Omron variable speed inverter drives at 999 Inverters