Connecting the holding brake: protection against electric shock requires safe separation through reinforced insulation

Question:

What has to be considered when connecting a holding brake to a drive controller with regard to personal protection?

Answer:

To protect persons from electric shock, a safe separation of the existing potentials is prescribed.

Standards: EN 61800-5-1, EN 50178, EN 60204-1:2006.

In particular, there must be no conductive connection between the potential of the 24V electronic supply with its touchable components (plug,...) and the dangerous voltage of the mains, inverter or motor.

Parts of the unit that can be touched by people must never come into contact with a dangerous voltage. Not even if an insulation fault has occurred at one point. This means that a double safety, the so-called SAFE SEPARATION, is required.

The potential separation for a SAFE DISCONNECTION must therefore be designed as follows (over the entire circuit between the unit and the holding brake):

Reinforced insulation: Insulation is rated for twice the voltage required for single insulation (basic insulation).
Double base insulation: Series connection of twice a base insulation.

For units that only have functional insulation between the 24V electronics supply and the brake terminals (without additional base insulation), consider the following:

The required double basic insulation must be provided for the cable routing, the terminals/plug connectors and the installation of the holding brake within the motor.
If the holding brake is connected via cores in the motor cable, the connectors on the motor can form a "weak point".
The 24V power supply for the brake must be provided by a separate 24V power supply unit which itself has the required safe isolation (SELF/PELV).

Conceivable measures if the electronics and the holding brake are to be supplied only via a 24V power supply unit:

Connection of the brake via a separate wire outside the motor cable and plug.

In case of connection via cores in the motor cable: Use of a DC-DC transformer for potential separation between brake module and 24V line in the motor cable.

Automatic Translation

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