Why Do Some VFDs Have Brakes? A Complete Guide to Braking Methods in Industrial Drives

Variable Frequency Drives (VFDs) are essential in modern automation, offering precise motor control and energy efficiency. But if you’ve ever looked closely at VFD specs or wiring diagrams, you may have seen mention of “braking” or “brake resistors.”

So what’s the deal? Why do some VFDs need brakes—while others don’t?

In this guide, we’ll break down the purpose of braking in VFDs, when it's needed, and how different braking methods work to protect your equipment and improve control.

What Is Braking in a VFD?

Braking in a VFD refers to how the drive handles excess energy generated when a motor slows down or stops. During deceleration, the motor acts as a generator, feeding energy back into the drive.

If this excess energy isn't properly managed, it can:

• Overload the drive’s internal DC bus
• Cause faults or shutdowns
• Damage components over time

That’s where braking comes in—it safely dissipates this energy to prevent system failure.

When Do You Need Braking?

Not every VFD needs a brake. Braking is required in applications where the motor decelerates quickly, stops frequently, or needs to hold a load in place.

Common scenarios include:

• Rapid deceleration – Conveyor systems, elevators, and spindles
• High-inertia loads – Fans, centrifuges, or large flywheels
• Frequent start/stop cycles – Packaging lines, hoists, indexing tables
• Vertical loads – Lifting applications where motors must resist gravity

If the system has high momentum or the load needs to stop quickly, braking is often necessary.

Types of Braking Used with VFDs

There are three primary braking strategies used with VFDs, each suited for different needs:

1. Dynamic Braking (Resistor Braking)

The most common method for high-inertia systems.

A braking resistor is connected to the VFD’s DC bus. When excess energy builds up during deceleration, the VFD routes it to the resistor, which converts it into heat and safely dissipates it.

Advantages:

• Simple, effective, and low-cost
• Ideal for stopping large, fast-moving loads
• Doesn’t feed power back into the grid (no need for synchronization)

Common Use Cases: Elevators, presses, conveyors, centrifugal machines

More Info: Dynamic braking is especially useful when stopping a motor quickly is more important than reclaiming energy. The resistor converts electrical energy into heat, which is why resistor sizing is critical—too small, and it may overheat and fail; too large, and it may not activate effectively. Engineers must calculate peak braking wattage and duty cycle to ensure proper operation. Most modern VFDs have built-in chopper circuits to direct the energy, but the resistors themselves must be added externally. Dynamic braking is a cost-effective solution that’s easy to retrofit on existing systems.

2. Regenerative Braking (Line Regeneration)

The energy-conscious option.

Instead of wasting the braking energy as heat, regenerative drives convert it into usable electricity and send it back into the power grid.

Advantages:

• Energy-efficient—can reduce power consumption in high-duty-cycle applications
• Keeps control cabinet cooler (no heat dissipation required)

Limitations:

• More expensive
• Requires system compatibility and line synchronization

Best For: Cranes, escalators, and energy-sensitive operations

More Info: Regenerative braking offers significant energy savings by routing the energy generated during deceleration back to the facility’s power network. This approach is ideal for facilities with frequent, heavy-duty braking where power recovery offsets upfront cost. Regenerative units or drives include power-inversion technology to convert DC back to grid-compatible AC. It’s often used in multi-axis setups, test benches, and vertical transport systems. Although more complex than dynamic braking, the long-term savings on energy and cooling costs make it a sustainable choice in the right environment.

3. DC Injection Braking

Used for holding torque or low-speed stopping.

In this method, DC voltage is injected into the stator windings of the motor after the VFD turns off the AC power. This holds the rotor in place and slows it down smoothly.

Advantages:

• Simple to implement for small systems
• Useful for holding position on light vertical loads

Limitations:

• Not suitable for large or high-inertia systems
• Produces heat in the motor windings—can cause overheating if overused

Common Uses: Saw blades, vertical lifts, or tools that need controlled stopping

More Info: DC injection braking is often built into the VFD and activated via parameter settings. It works well for soft stopping or holding torque at zero speed, such as stopping a blade in woodworking or holding a lift motor in place. However, it should be applied cautiously—extended braking periods can cause the motor to overheat due to continuous DC current flow in the windings. For this reason, DC injection is typically limited to short bursts (a few seconds or less). It’s also unsuitable for high-inertia systems where more powerful braking is required.

How to Know If Your VFD Supports Braking

Most modern VFDs include internal braking choppers—circuits that manage the transfer of braking energy to an external resistor. However, not all drives come with this by default.

When evaluating a VFD for braking:

• Check if a braking chopper is built-in or needs to be added externally
• Review resistor sizing guidelines in the user manual
• Confirm whether regenerative options are supported (for energy feedback systems)

Always follow the manufacturer’s recommendations—improper braking setups can void warranties or damage your drive.

Braking and Safety Considerations

Braking systems aren’t just about performance—they’re about safety, too.

Proper braking improves:

• Machine control – Especially in emergency stop situations
• Load stability – Preventing drift or rollback in hoists and elevators
• Motor lifespan – By reducing stress and preventing overheating
• Drive protection – Avoiding overvoltage faults and unplanned downtime

If your system involves motion that must stop quickly or precisely, proper braking isn’t optional—it’s essential.

Final Thoughts

Braking in VFDs is a critical part of safe, responsive, and efficient motor control—especially in high-inertia, high-speed, or high-precision environments. While not every system needs braking, many do—and using the right method can make the difference between smooth performance and costly faults.

At Industrial Automation Co., we supply VFDs, braking resistors, and technical guidance to keep your systems running safely and efficiently. Whether you’re building a new system or retrofitting an old one, our experts are here to help.

Have a braking question or need help choosing a VFD? Contact us today.