Externally mounted, half controlled 3-phase field exciter, with single quadrant operation. This field supply is current regulated with a max output current of 35 amps. With 1-phase input, an autotransformer is recommended for voltage adaptation. An input line reactor is required when supply voltage is over 400 Vac. Fuses are always required. DSL communication cable is required. Communication to the converter unit is required via the SDC-DSL-4 board, standard in D5-D7 and all drives 600 Vdc or greater, otherwise optional.