The AC/DC sensitive MRCDB300 device series is used as additional protection (protection against indirect contact) in earthed systems (TN and TT systems) in which AC or DC fault currents may occur.
Part of these systems are particularly loads containing six-pulse rectifiers or one-way rectifiers with smoothing, such as converters, battery chargers, construction site equipment with frequency-controlled drives. When the response value IΔn2 (alarm) is reached, the output relays K1 and K2 switch.
By using an MRCDB300 module and a switching element with isolating properties, the device combination fulfils the requirements of IEC 60947-2 Annex M for an MRCD protective device.
The application is specifically intended for protection goals such as protection of persons, fire protection and plant protection. The switching element must not exceed a switch-off time of 20 ms.
The residual current monitoring modules each consist of the MRCDB300 evaluation electronics and a CTBC20(P)…210(P) series measuring current transformer core. To assemble a complete module, both the electronics and a measuring current transformer core are required; if ordered separately, these two components must then be plugged together and calibrated during commissioning.
The CTBC20P…210P series measuring current transformers feature an integrated magnetic shield and are suitable for applications with high load currents or inrush currents.