Description
3.3 Accessories
Installation and Operating Instructions SINAMICS G180
Operating Instructions, 02/2019, 4BS0751-007
49
3.3.3
Brake transistor and brake resistor
During motor operation the electrical power flow is from the inverter to the motor. During
generator operation the electrical power flow is from the motor to the inverter.
Example: braking flywheels.
The DC link current reverses the direction. The standard version of the inverter cannot feed
energy back into the system. Kinetic energy can be converted into dissipated heat in braking
operation. Approx. 10% braking torque is available in the upper speed range. A braking
torque of up to 50% without additional equipment is achieved in the medium and lower
speed ranges by oversaturation of the motor. With the brake transistor accessory, the same
braking as driving torque is available. The energy occurring is converted to heat using a
pulsed transistor. Also connect an external brake resistor.
WARNING
Risk of fire
If the clearance between the resistors and the neighboring components is selected too
small, fire can occur due to overheating. This can result in death, serious injury or material
damage.
Maintain a minimum clearance of 200 mm.
3.3.3.1
Dimensioning the brake resistor
Select a resistance value of at least that stated in the technical data. This value corresponds
to the minimum configurable value. The maximum value is calculated from the following
equation:
R = (1.57 × U
mains
)² / P
brake
3.3.3.2
Connecting the brake resistor
1.
Using the device designation on the rating plate of the device, check whether you have a
device with the "brake resistor" option. The designation must be ...2T..-.....-...B....
For more detailed information, refer to section "Type designations" (Page 31).
2.
Connect the external braking resistor at terminals -X1:R and -X1:UD2+.
3.
Use shielded cables with concentric protective conductor or shielded cables to connect
the brake resistor. Connect the shield where the cable enters the inverter.
4.
Set the parameter "P-INVERTER DATA/Brake" to "On".
5.
Set the rated output of the resistor under "/P-BrakeRes." and the resistance value under
"/R-BrakeRes.". In this way, you prevent overloading of the resistor.
