What is a brake resistor and what is it used for?

A brake resistor is sometimes used with electric motors. But what does it actually do and what are its benefits?

The setup of an electric motor is very similar to that of a generator. A motor can, therefore, not only convert electrical energy into mechanical motion, but also generates electrical voltage at the same time. This appears contradictory at first glance as energy is supplied to the motor to generate rotary movement. However, this behaviour is a basic principle of electrical machines and based on electromagnetic induction. In technical terms, this generated voltage is known as the "counter electromotive force" (or CEMF). It counteracts the input voltage and builds up with increasing speed. This is one of the reasons why a motor's torque decreases at high speeds.

What does this have to do with the brake resistor?

In the braking process, the motor control system reduces the motor speed. In DC motors, this is done by reducing the motor voltage output. Inertia converts the kinetic energy remaining in the system into electrical energy (generator principle, as described above). This electrical energy can damage the control system or other voltage system components. The brake resistor creates a consumer for this energy and converts it to heat. Thus, a brake resistor allows for quick braking even with heavy loads.

When do we recommend a brake resistor for our control system?

Currently, a brake resistor can only be used with the D1 motor control system in conjunction with a BLDC or a DC motor. In the manual, we go into a great deal of detail about the brake resistor's design and make recommendations. A good rule of thumb is that you need a brake resistor if you want to brake high loads quickly.

If you require a precise analysis, please do not hesitate to contact us.

Can the motor be moved by hand if the control system is switched off?

It is possible to move the motor or linear axis when the control system is switched off. However, it might be necessary to re-reference the system. If the control system or the release is switched off, nothing can go wrong under normal circumstances. Referencing is only necessary if X1.3 was not under power.

How much does a brake resistor cost?

igus-compatible brake resistors cost between €6 and €12 per piece. Despite their low acquisition costs, the products make a big technical difference and protect the more cost-intensive components, such as the control system.

What brake resistors does igus offer?

We recommend the following brake resistors for the indicated motor sizes:

Motor	Resistance value	Power
MOT-EC-42-XXX	18 Ω	15W to 35W
MOT-EC-56-XXX	4.7Ω	25W to 65W
MOT-EC-60-XXX	3.3Ω	50W to 85W
MOT-EC-86-XXX	2.8Ω	50W to 100W

How do I hook up a brake resistor?

You can find a detailed description in the D1 motor control system manual. As a general rule, this is an output that the brake resistor can be wired to.