Monitoring the voltage with the MDP92A-..

The brake chopper can be parameterized here for the MDP92A-.. power supply module.

The device has a connection for an external discharge resistor on the A-side. This is actuated by the internal brake chopper, and can be used to discharge the DC link connected on the A-side.

The resistor on the A-side can be activated using control word 8809.9 "External resistor – control word".

If automatic mode is activated via parameter 8809.13 "External resistor – automatic mode" (default value is "On"), the external resistor fulfills a brake chopper function.

It is activated automatically if the voltage that is set via the parameter 8809.11 "Brake chopper switch-on threshold" has been reached on the A-side.

It is switched off if the voltage has dropped below the value set via parameter 8809.12 "Brake chopper hysteresis". It can still be activated manually with a higher priority using control word 8809.9 "External resistor – control word".

However, the resistor is only switched off if automatic mode and the control word signal that deactivation has taken place.

If an overcurrent occurs in the brake chopper branch, the brake chopper is inhibited by the device. Fault E4.1 "Brake chopper overcurrent" is executed.

If connector X7 signals a fault of an external braking resistor, the brake chopper and the output stage are inhibited. Fault E26.4 "External braking resistor fault" is executed.

The status of the external resistor can be read via parameter 8809.112. If a fault is present, the status bit for connection is deleted or the bit for disconnection is set. If necessary, these can be used to disconnect the external resistor from the system using a switch. For example, this is useful if a storage unit is installed which then also remains connected to the resistor in the event of a fault, and discharges its energy content via the resistor. The bit which activates the brake chopper is also deleted in the event of a fault.

• Bit 0: Active: the brake chopper has activated the external resistor.
• Bit 1: Connect: the external resistor is to be connected, e.g. via an external switch.
• Bit 2: Disconnect: the external resistor is to be disconnected, e.g. via an external switch.