During power on powerful supply, there is a high charging current. This current can to destroy the components. To exclude those troubles - this Step-Start Unit is intended.Rectifier diode protection, must be for charging big capacity capacitors. High charging current is arises in the moment of switching on. The scheme of gradual start\" (\"soft start\") was developed for decrease initial charging rate at the switching on moment. After switching on - 220V comes to the power supply unit through powerful resistor that can limits starting current. After some time - this resistor will be closed, by the relay contacts and the power supply is ready to use.Step-Start Unit is used in a linear amplifierDN-600.You can see on this picture what is inside the DN-600:

1.Power supply SE-1000-48, 2.Heat sink, 3.Step-Start Unit, 4.Fan EEC02151B1, 5.LPF600 Unit, 6.PA Unit, 7.ATT Unit

---