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Applications and How-Tos

AGV and Forklift Motor Brakes | Fail-safe brake technology

Jonathan Bullick | February 28th, 2018

An AGV is an Automated Guided Vehicle. The vehicle is typically motor-driven and rides on wheels. KEB’s brakes can be used as a fail-safe emergency stop brake. This post provides an overview of using KEB brakes in AGV applications.

failsafe springset brakes
See how KEB spring-set brakes work

AGV motor brake solutions: Why fail-safe brakes?

A fail-safe brake is one that works in the event that power is cut to the machine. In the KEB world, this is our COMBISTOP line of brakes.

In summary, a spring-applied brake works with springs pushing the armature across onto the friction surface causing the shaft to stop moving, or prevent it from moving. When power is applied, an electromagnet energizes and pulls the armature back, overpowering the springs. With the brake powered, the AGV would be allowed to move.

An example of when this fail-safe brake would be used is when a very heavy AGV is out in the field, and the motor loses power on an incline. This would make the AGV subject to gravity, and if anyone were standing lower on the hill, or behind the AGV, they could be in serious danger. The fail-safe spring-applied brakes would kick in as soon as the power is lost, and all dangers would be exhausted.


COMBISTOP spring applied brakes

Brake size

KEB brakes have the capability of producing a high amount of torque in a relatively small physical package. This way they can fit on even small applications. KEB spring-set brakes can be engineered and selected for both parking (holding) or dynamic brake applications. Additionally, KEB has engineered special solutions that are capable of high energy e-stops – these are used to stop AGVs with particularly large masses.

IP rating

KEB is capable of creating a brake with up to an IP 65 rating. This means that they can handle high humidity and dust infiltration.


OEX rectification

KEB offers an OEX rectifier for a fast response. As in the example listed above, we would like to prevent the AGV from rolling backwards at all and gaining momentum. Simple physics says that something with a lot of inertia is harder to stop. So the faster switching times we can obtain, the better. OEX rectification also reduces power consumption, and reduces heat generation.

KEB’s 24V powerbox actually provides both functions built into one switch. It overexcites to provide fast brake release, but then lowers the holding voltage which lowers power consumption and increases battery life.


AGV motor brake - microswitch option
An optional microswitch can be added to the brake.



KEB’s COMBISTOP brakes can be equipped with a built-in hand release so that you could manually transport the AGV even without power applied. KEB’s brakes can also be fitted with an optional microswitch. Microswitches can be used in two ways. First, the microswitch can be set so that it closes when brake engages. This gives the controller confirmation that power can be cut to the motor. Secondly, the microswitch can be used as a wear indicator for the friction lining. The switch will open, indicating that the brake should be proactively serviced before the airgap becomes too large and the brake stops operating.

As with the heart of KEB’s magnetic products, there is plenty of room for customization to your application. Whether you need high torque in a small physical footprint or you need a special flange, or almost any other adaption you require, we can customize for you.


If you have a question about AGV motor brake solutions – like the COMBISTOP line of brakes from KEB America – send us a note from the form below.


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