Response of the new version:
If the 24V-electronics supply fails or is interrupted for a short time, the brake output switches immediately without delay.
I.e. the holding brake is applied as soon as possible.
What happens? After response of the 24V-electronics supply monitoring, the brake output is only controlled after a certain time delay.
Accordingly, the holding brake is applied correspondingly later. During the time delay, the inverter is already inhibited, so that the motor is no longer energised and can no longer generate any torque.
The duration of the time delay depends on whether the 24V-electronics supply has permanently failed or has only been interrupted for a short period of time:
Case 1: Permanent failure of the 24V-supply (for at least 200 ms and longer): Time delay of approx. 0.2 s
Case 2: Short-time interruption of the 24V-supply (interruption of less than 200 ms): Time delay of approx. 2.5 s
When does this problem occur? - The controller is enabled and the brake is released, and
- in this operating status, the 24V-electronics supply monitoring responds and as a result of this, the inverter is inhibited immediately.
Which products are affected?
- i700 servo Inverter ≤ V01.06.03.9953
Short-term measures/recommendations:
In the case of an intended switch-off of the 24V-electronics supply (like case 1):
- First, inhibit the controller to ensure that the brake can properly accept the load,
- only after this, switch off the 24V-supply.
In the case of an unpredictable short-time interruption of the 24V-electronics supply (like case 2):
- The user must ensure an uninterruptible and stable 24V-electronics supply. The 24V-supply must not be interrupted, see i700 hardware manual.
- The 24V-power supply unit must be powerful enough and adequately buffered to ensure that the 24V-voltage supply will be stable with a maximum ripple.
- The 24V-electronics supply and the 24V-supply for the brakes should be separated using separate power supply units (see documentation for i700).
On the one hand, separate power supply units are required to ensure the electrical isolation (double basic insulation) required for the protection of persons, and, on the other hand, to avoid interfererences of the 24V-electronics supply by switching the brake coils (inductances).
Evaluation:
The additional time delay occurring when switching the brake may have an effect on the behaviour of the application and must be considered, in particular in the case of active loads, such as hoists, which may be sagging while the brake is not applied.
Important note for hoist applications and other applications where major damage may arise if the brake fails or is only applied with delay:
- It is up to the mechanical engineer to carry out a risk analysis and, if necessary, to provide for a second independent brake system to avoid potential damage.
