Hey there! As a supplier of 30KW VFDs, I often get asked about how to set the braking parameters of these drives. It's a crucial aspect that can significantly impact the performance and safety of the equipment they're used with. So, in this blog, I'm gonna walk you through the process step by step.
First off, let's understand why we need braking in a VFD. When a motor is running, it has kinetic energy. When you want to stop the motor quickly, you need to dissipate this energy. That's where braking comes in. There are mainly two types of braking methods for VFDs: dynamic braking and regenerative braking.
Dynamic Braking
Dynamic braking works by converting the kinetic energy of the motor into heat through a braking resistor. When the VFD decelerates the motor, the motor acts as a generator, producing electrical energy. This energy is then sent to the braking resistor, which dissipates it as heat.
Step 1: Determine the Braking Torque
The first thing you need to do is figure out the braking torque required. This depends on the load inertia, the deceleration time, and the motor's rated torque. The formula for calculating the braking torque is:
[T_b=\frac{2\pi J (n_1 - n_2)}{60t_d}+T_L]
Where:
- (T_b) is the braking torque (N.m)
- (J) is the total inertia of the load and motor (kg.m²)
- (n_1) is the initial speed (rpm)
- (n_2) is the final speed (rpm)
- (t_d) is the deceleration time (s)
- (T_L) is the load torque (N.m)
You can usually find the motor's rated torque in its datasheet. The load inertia might require some measurements or calculations based on the mechanical system.
Step 2: Select the Braking Resistor
Once you have the braking torque, you can select the appropriate braking resistor. The power rating of the braking resistor is calculated based on the braking energy and the duty cycle. The formula for the power rating of the braking resistor is:
[P_{br}=\frac{E_b}{t_d}]
Where:
- (P_{br}) is the power rating of the braking resistor (W)
- (E_b) is the braking energy (J)
The braking energy can be calculated using the formula:
[E_b=\frac{1}{2}J\omega_1^2-\frac{1}{2}J\omega_2^2]
Where:
- (\omega_1) is the initial angular velocity (rad/s)
- (\omega_2) is the final angular velocity (rad/s)
It's important to choose a braking resistor with a power rating that can handle the calculated power. You also need to consider the resistor's resistance value, which affects the braking current and the braking torque.
Step 3: Set the Braking Parameters in the VFD
After selecting the braking resistor, you need to set the relevant parameters in the VFD. These parameters typically include the braking torque limit, the braking frequency, and the braking time.
- Braking Torque Limit: This parameter sets the maximum braking torque that the VFD can apply. You should set it based on the calculated braking torque.
- Braking Frequency: This determines how often the braking function is activated. You need to set it according to the application requirements.
- Braking Time: This is the time it takes for the motor to stop. You can adjust it based on the deceleration time you calculated earlier.
Regenerative Braking
Regenerative braking, on the other hand, recovers the kinetic energy of the motor and feeds it back to the power supply. This is more energy - efficient than dynamic braking, especially in applications where there are frequent stops and starts.
Step 1: Check the VFD's Compatibility
Not all VFDs support regenerative braking. So, the first step is to check if your 30KW VFD is capable of regenerative braking. Some high - end VFDs, like our Synchronous Motor Drive, have this feature built - in.
Step 2: Install the Regenerative Unit
If your VFD supports regenerative braking, you need to install a regenerative unit. This unit converts the DC voltage generated by the motor during braking into AC voltage and feeds it back to the power supply.
Step 3: Set the Regenerative Parameters
Similar to dynamic braking, you need to set the relevant parameters in the VFD for regenerative braking. These parameters include the regenerative torque limit, the regenerative frequency, and the power feedback limit.
- Regenerative Torque Limit: This sets the maximum torque that the VFD can regenerate. It should be set based on the motor's capabilities and the application requirements.
- Regenerative Frequency: This determines how often the regenerative function is activated.
- Power Feedback Limit: This limits the amount of power that can be fed back to the power supply.
Tips for Setting Braking Parameters
- Test and Adjust: After setting the initial parameters, it's important to test the system and make adjustments as needed. You might need to fine - tune the parameters to achieve the desired braking performance.
- Consider the Environment: The ambient temperature can affect the performance of the braking resistor. In high - temperature environments, you might need to choose a braking resistor with a higher power rating.
- Follow the Manufacturer's Guidelines: Always refer to the VFD's user manual for specific instructions on setting the braking parameters. Our 30KW VFD comes with a detailed manual that can guide you through the process.
Conclusion
Setting the braking parameters of a 30KW VFD is a crucial task that requires careful consideration of various factors. Whether you choose dynamic braking or regenerative braking, following the steps outlined above will help you achieve optimal performance and safety.
If you're in the market for a reliable 30KW VFD or need more information on setting the braking parameters, don't hesitate to reach out. Our VF Control VFD is a great option for a wide range of applications. We're here to assist you with all your VFD needs and ensure that you get the most out of your equipment. Contact us today to start the procurement process and let's discuss how we can meet your specific requirements.
References
- VFD User Manuals
- Electrical Engineering Textbooks on Motor Drives
- Industry Standards for VFD Braking Systems