Project planning for 4-quadrant operation with brake chopper and braking resistor
In regenerative operation (4Q braking operation) of the drive, energy is fed into the supply circuit. This may result in an increase of the voltage at the drive and at the output of the 48 V DC current supply.
A DC compound with multiple drives enables efficient energy exchange between different drives in different operating states. The regenerative braking energy of individual drives can be fed back to the other drives and be used for the motoring operation.
Many mobile applications in 48 V DC are powered by energy storage units. In these applications, no external brake chopper is normally required because regenerative energy can be fed back into the storage units. If this is not possible or cannot be done quickly enough, external brake choppers are used that switch just below 60 V DC.
The function of the brake chopper is to dissipate, in the form of heat, the regenerative energy that cannot be buffered during rapid speed changes or lifting applications. If the set voltage threshold is exceeded, the external resistor is switched on to prevent a damaging overvoltage.
INFORMATION
- The braking resistor and the brake chopper are not included in the scope of delivery.
- Configure the braking resistor and brake chopper according to the operating instructions. (Observe maximum power loss.)
The drive configuration determines whether the installation of a brake chopper module is required and how much energy must be dissipated. The power values can be doubled by using 2 braking resistors (parallel connection = 4.4 ohms) on a brake chopper module.
Possible values with the recommended braking resistor BW009-0005 (8.8 Ohm) and a 48 V DC voltage supply.
Property | Value |
|---|---|
Brake chopper response threshold | 54 V |
Current with active brake chopper | 6.2 A |
Peak power | 330 W |
Continuous power/effective output | 50 W |
Values when using 2 resistors on a brake chopper module (parallel connection = 4.4 ohms).
Property | Value |
|---|---|
Brake chopper response threshold | 54 V |
Current with active brake chopper | 12.3 A |
Peak power | 660 W |
Continuous power/effective output | 100 W |
The current flows through the braking resistor until the voltage drops below the switch-off threshold of the brake chopper. In the process, the braking energy is converted into heat. Optimum cooling is a prerequisite for the continuous power rating of the braking resistor.
After startup, the correct setting of the response threshold and the designated use must be checked.
