3 Engineering | LXM32 |
3.5Braking resistors
Excess energy in the common DC bus must be absorbed by the brak- ing resistors. Depending on the application, one or more braking resis- tors can be connected. Consider the internal braking resistors of LXM32 drives in your calculations.
If drives with a different nominal power are connected via the DC bus, you must connect braking resistors to the drive with the highest nomi- nal power. See the manual of the respective product for more informa- tion.
3.5.1Rating the braking resistor
An insufficiently rated braking resistor can cause overvoltage on the DC bus. Overvoltage on the DC bus causes the power stage to be disabled. The motor is no longer actively decelerated.
WARNING
MOTOR WITHOUT BRAKING EFFECT
•Verify that the braking resistor has a sufficient rating.
•Verify that the parameter settings for the braking resistor are cor- rect.
•Verify that the I2t value for temperature monitoring does not exceed 100% by performing a test run under maximum load con- ditions.
•Verify that the calculations and the test run take into account the fact that the DC bus capacitors can absorb less braking energy at higher mains voltages.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
The temperature of the braking resistor may exceed 250 °C (482 °F) during operation.
WARNING
HOT SURFACES
•Ensure that any contact with a hot braking resistor is avoided.
•Do not allow flammable or
•Verify that the heat dissipation is sufficient by performing a test run under maximum load conditions.
Failure to follow these instructions can result in death, serious injury, or equipment damage.
Braking resistors are required for dynamic applications. During decel- eration, the kinetic energy is transformed into electrical energy in the motor. The electrical energy increases the DC bus voltage. The brak- ing resistor is activated when the defined threshold value is exceeded. The braking resistor transforms electrical energy into heat. If highly dynamic deceleration is required, the braking resistor must be well adapted to the system.
MNA01M001EN, V1.01, 08.2014
32 | Common DC bus |
