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KEB Technology

Permanent Magnet Servo Motor Brakes

Jonathan Bullick | December 18th, 2021

Servo motor applications often need integrated servo motor brakes for applications that require power-off static (holding) braking or the occasional emergency stop.


brake in servo motor
KEB offers servo motor brakes up to 145Nm


Integrating the brake into the servo motor housing rather than externally mounting saves on overall system design work, space, and ease for the customer. The servo motor industry is getting smaller (motor design-wise), but still expects the same or better performance in regards to efficiency and torque.


KEB’s Permanent Magnet Brake also referred to as a PM brake, is a proven solution to work effectively and safely when integrated inside a servo motor.  If you are not yet aware of how a Permanent Magnet Brake operates, this video gives an overview.



Advantages of KEB PM Brakes

KEB’s permanent magnet brakes have many advantages over the traditional spring-set type that is sometimes used. To name a few, KEB PM brakes have the following characteristics:

  • Lower inertia
  • High maximum speeds
  • Backlash free operation
  • Quicker brake engagement
  • Highest torque density (torque to diameter ratio)
  • ISO Class F or H insulation
  • Flexible design for integration purposes


Zero Backlash, Dynamic performance

KEB PM brakes were designed with servo motor applications in mind. For servo motor efficiency and dynamic operation, our brakes have a very low inertia compared to the motor and the more traditionally used spring-set brake.

Our PM Brakes also do not limit the servo motor speed; depending on the size they can operate up to 10,000 rpm. We use a riveted connection, allowing the brake to be backlash free.


servo motor brake
Permanent Magnet brakes can be rated for use up to 10,000 RPMs


This is important for applications requiring no movement, like robotics or medical machines, when the brake is applied. It can also deliver the needed braking torque almost instantaneously (a few milliseconds), which is crucial for those occasional emergency stops.


Compact – Best-in-class Torque Density

As I previously said, the servo motor envelope is always getting smaller with the same or better performance, which in return means the brake needs to do the same. Our PM brake solution is our highest torque density brake (high torque in small package) we offer, which is ideal for these servo motor designs.


Compared to spring-set types, KEB PM brakes are approximately 33% smaller for an equivalent torque rating.


It should be stated that if the application absolutely requires a fail-safe brake, then you would need a KEB Spring-Set Brake. However, KEB Permanent Magnet Brakes have been used for applications requiring the highest degree of safety, an example being medical surgical robots, and are reliable when installed and operated correctly. They are currently installed in thousands of servo motors from different manufacturers worldwide in a wide array of applications.


Customized – For your motor and assembly

Applications are getting more and more complicated and often require customization to do exactly what the customer requires. We understand that and can work with you on designing an integrated PM brake for your Servo Motor to make the assembly and design as simple as possible, while still maintaining a high degree of safety and performance.


We have proven this technology in the market and there are certain advantages to why a Permanent Magnet Brake is the correct brake technology for varying Servo Motor applications.


custom servo brakes
KEB offers special brake designs that ease assembly


Contact a KEB America engineer if your Servo Motor needs an integrated brake and we will work with you to find the right solution for your application.


(First published Jun 18, 2015) 

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