Question:
Which aspects are to be considered when a DC-bus connection with 230 V devices is to be established if the devices are supplied via the phase voltage of a 400 V TN system?
Answer:
If 230 V devices (L, N) are connected to a 400 V TN system the devices are supplied with the phase voltage (230 V). In most cases the devices are distributed on the different phases in order to achieve an even mains load.
If a DC-bus connection is established it is in case of this connection constellation only allowed interconnecting those devices to the DC bus which are supplied by the same phase. If devices which are supplied by different phases are interconnected to a DC bus a three-phase bridge connection results from the single-phase bridge connection of the devices and the DC-bus connection. As a result, the 400 V mains is rectified and 560 V DC is applied at the DC bus of the devices.
This situation inevitably leads to the destruction of the device.
This restriction does not occur if the devices are supplied via a 230 V system (single phase or three-phase).
