And what was the first thing you did when you drove off again? That’s right, you probably applied the brakes a little harder—to “brake” the layer of rust off the pads.
And exactly the same phenomenon occurs with holding brakes for electric motors – for example, permanent magnet brakes.
In practice, this results in the following:
The nominal braking torque of a brake does not always correspond to the actual braking torque. The nominal torque is the ideal case when the brake is perfectly synchronized – i.e., as in a car, the friction surface is completely free of oxidation, etc. In practice, the holding torque can drop to up to 50% of this nominal torque. This is then the minimum static holding torque. Conversely, this means that you should pay particular attention to this minimum static holding torque! It gives you a reliable indication of how far the braking torque can drop. You can carry out maintenance runs on your machine – as with the car above – then you can also work with higher values. But then it depends on how often you can perform the maintenance runs.
So, in conclusion, as a rule of thumb: the holding torque of a brake can drop to 50% of the nominal torque.
Note:
In applications, people often only talk about the nominal torque (i.e., the ideal case), not the lowest braking torque of a brake.
Now you know that you should always ask about the minimum braking torque – without maintenance run-in. 😎
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