Network over-voltage protection device for mains-operated load

摘要

The over-voltage protection device uses a bipolar power transistor (T1,T2) inserted into each supply line in series with the load (V) and an associated control device normally holding each transistor blocking path in the min. voltage condition. The control device responds to a mains over-voltage to provide a voltage drop across the transistor blocking path which ensures a max. voltage output, for switching the transistor to protect the load. The control terminal of the transistor is supplied via a voltage limiting element, e.g. a suppressor diode, or Zener diode (ZD1,ZD2), with a power resistance between the control terminal and the input terminal of the blocking path.