The "Overvoltage protection" OVP serves to protect the connected load for
overvoltage, which may be caus ed by either a faulty regulation system or
by abusive adjustment of the controls on the front panel.
The protection obh-:ins own reference voltage fron Z lOO.
The voltage divider Rl0l+P105, R102+ Pl00 is designed so that, as long as
the output voltage is lower than the OVP is set to (PlOO), the voltage at the
bas e of TlOO is positive. If the output voltage exceeds the OVP limit, TlOO
is actuated and thyristor SCR lOO is fired. The out· ut is cons equently short
circuited. If the OVP is actuated e. g. by abusive setting of the controls and
RAC PAC operates normally, the power supply switches over to current limit
with output voltage near zero .
The power supply is reset by setting the ;; . •ntrols on the front panel in
correct position and switching off the line.
If the current limit does not function e. g. in case of a sh'.'Jrt-circuit in the
series regulator, fr e fus e F2 (OV P fuse) is blown.
Then the fault has to be located and F2 is to be replaced.
When P95 is in full CW position, switch 83 is opened and the OVP is not
working.
37
