Electromagnetic Brakes

Electromagnetic brakes are devices that rely on electromagnetic force to hold loads in place. There are several variations available, all of which operate on the same principle—applying an electrical current through an electromagnetic coil to create a magnetic field strong enough to move an armature on or off of a magnetic face. The friction surface is what generates the necessary braking torque. These braking systems are used in aerospace and defense applications, robotics, medical systems, and many others that require quick response times and consistent performance. SEPAC is a clutch and brake solutions provider specializing in the design and manufacture of spring-engaged and magnetically-engaged electromagnetic brakes for a range of high-performance and safety-critical applications.

Types of Electromagnetic Brakes Available at SEPAC

Spring-engaged or power-off brakes and magnetically-engaged or power-on brakes are two distinct categories of electromagnetic brakes that differ in design and operation. With spring-engaged or power-off designs, the brake is designed to be engaged when power is turned off. In this spring engaged state, the compression springs apply pressure to the armature plate, pushing it into the friction disc to prevent rotation. When power is returned to the coil, the brake disengages and the shaft can then rotate freely.

SEPAC offers the following spring-engaged power-off brake designs:

• Tooth Brake (SETB) Series: Spring-engaged tooth brakes use springs to force the armature’s teeth into engagement when current is removed.
• Spring Engaged Brake (SEB) Series: Standard friction brakes utilize friction discs to transmit torque upon compression, stopping or holding a load when power is off. The SEB product line can be customized based on the application and friction material can be selected for the highest performance.
• Thin Spring Engaged Brake (TSEB) Series: Our low-cost thin spring designs feature a thinner profile relative to standard spring-engaged designs, giving them an excellent torque-to-size ratio.
• Ultra Thin Spring Engaged Brake (UTSEB) Series: The ultra thin brake  features the thinnest profile of our power-off brakes, making it well-suited for accommodating space limitations and utilizes a PWM to step down the voltage.
• Manual Release Spring Engaged Brake (MSEB) Series: Our manual release brakes are equipped with a lever that provides a manual override in the absence of power.

In contrast to power-off brakes, magnetically-engaged or power-on brakes are designed to engage when the power is turned on. In the absence of power, the armature is disengaged from the body of the magnet and can rotate freely. Release springs positioned between the armature and output plate help hold the armature in this disengaged position. When power is supplied to the coil, the armature engages with the magnet body, and the attached load can be held. SEPAC’s magnetically-engaged power-on tooth brakes come in a range of sizes with various torque ratings and speed capacities.  

Electromagnetic Brake Capabilities & Specifications

Electromagnetic brakes are sophisticated assemblies that provide fast response times; high torque; and can be designed for smooth, zero-backlash operation. Regardless of their specific designs and features, however, all electromagnetic brakes can perform one or all of the following basic functions:

• Decelerating a load
• Stopping a load
• Static holding

The electromagnetic brake’s specific design and engagement method will dictate the types of applications for which it is best suited. For example, while tooth brakes are excellent for static or holding-only applications, their positive locking nature makes them unsuitable for operations requiring dynamic engagement. Electromagnetic brake designs utilizing friction discs, on the other hand, provide the controlled, gradual deceleration required to accommodate dynamic engagement or stopping. Specific electromagnetic brake designs and their engagement mechanisms are explored in more detail below.

Spring-Engaged Power-Off Brakes

Spring-engaged friction brakes rely on spring pressure to force the armature plate into the friction disc when power is turned off and the electromagnetic field has dissipated. The resulting compression of the friction disc between the armature plate and pressure plate transmits torque which allows the brake to halt or hold attached loads in the absence of power.

Spring-engaged power-off brakes are often used in applications that require an emergency stop function in the event of a power failure. Other common applications include:

• Actuators
• Robotics Arms
• Motors
• Hoists
• Flight control surfaces

Magnetically-Engaged Power-On Brakes

In magnetically-engaged power-on tooth brakes, interlocking teeth between the armature and output plate enhance the brake’s torque capability and holding properties. These power-on brakes are activated when current is applied to the coil. The current generates a strong magnetic attraction that allows the armature to override the release springs, slide into the output plate’s splines, and engage with the magnet body. As the teeth engage, the attached load can be stopped or held. 

The strength and friction of the magnetic field generated in power-on brakes provide the force necessary to halt rotational motion. This type of braking action is required in the following applications:

• Elevation actuators
• Valve actuators
• Positioning systems
• Doors

Electromagnetic Brake Advantages & Benefits 

Electromagnetic brakes provide many benefits over alternative braking solutions, including:

• Reduced wear. The amount of friction required to slow or stop loads in mechanical braking systems can create significant wear and tear on the components of the brake over time. By using electromagnetic force and the properly selected friction material to provide the slowing/stopping action, electromagnetic brakes help reduce wear.
• Enhanced performance. An electromagnetic brake can be customized to provide fast action, precise engagement, and smooth, backlash-free operation.
• Lower costs. By reducing component wear and improving brake efficiency, electromagnetic braking solutions last longer and require considerably less maintenance.
• Improved heat dissipation. Well-designed electromagnetic braking systems can be highly effective at dissipating heat compared with mechanical systems and other alternatives.

Permanent Magnet Brakes

The integration of permanent magnets in permanent magnet brakes allows for the continuous generation of magnetic fields without the flow of current. These fields force the armature plate to engage with the brake’s friction surfaces in the absence of power. The application of sufficient power enables the brake to create a flux path that counters the one created by the permanent magnets, allowing the armature to disengage from the friction faces.

The commercial permanent magnet brakes we offer are suitable for dry applications. They provide a high torque density to size ratio (static torque capabilities range from 0.3 to 103.3 lbs per foot.) While they are primarily used for static holding operations, they can also be used for dynamic braking with zero backlash.

Electromagnetic Brakes from SEPAC

When properly matched to its application, an electromagnetic brake can enhance the efficiency and safety of an operation while reducing wear, maintenance, and downtime. At SEPAC, we understand the often-critical nature of braking applications, and we work closely with customers from diverse industries to provide high-performance, reliable electromagnetic braking solutions that can withstand the most demanding environments. In addition to our wide selection of off-the-shelf products, we also have the design experience and manufacturing capabilities to custom-design solutions for unique or specialized braking applications.

To learn more about our electromagnetic brakes and how they can be tailored to meet your needs, please contact us or request a quote today.