As there was no demand on galvanic separation, we chose a three phase auto transformer - due to this choice we could also redeem the size and weight requirements.
With the help of a transformer switch relais the current inrush at start up (also during load) is avoided. The usual mains fuses won’t blow because of the start up process.
The different output voltages were done on the transformer via taps on the coils. They are lead to the outputs by means of a power stage switch.
Accordingly to the switch position of the on-load tap-changer the set output voltage as well as the load depending output current is displayed on analog instruments. Conform to customer wish, we mounted off-the-shelf 5-pin CEE sockets that are used for the inputs and outputs. The complete unit is fastened in a steel metal sheet housing (protection class IP23) with rolls for an easy transport.