Manual
www.schaeferpower.de
Options & Accessories  Options & Accessories  
for Switch Mode Units
Options & Accessories  
Schaefer offers the industry’s most 
complete range of input and output 
voltages, combined with a selection 
of package style, mounting solutions, 
options for input and output as well as 
various possibilities of programming & 
monitoring.
Configuration of model designation:
Add the designation of options to 
the type number of the power supply 
module, e.g. C 3674-w-dr-eu1. 
Input
i inrush current limiting
A thermistor is connected in series with the input lines which changes its resistance from 
high to low when it gets hot. It does not reduce the surge current if the input power 
is interrupted for a short period of time not allowing the thermistor to cool down. 
Thermistors are fitted as standard to all mains input models except for 1-phase input 
of models > 2.5 kW. Thermistors are available up to 45A. For higher input current an 
electronic inrush current limitation can be offered.
ie electronic inrush current limiting
An electronic circuit limits the high inrush current caused by built-in capacitors. Switch- 
on time may increase to 5s.
This is realized by a series pass transistor or depending on the input voltage by thyristor 
softstart.
sd reverse polarity protection for DC input by series diode
A series diode protects the module against DC input voltage of wrong polarity. However, 
this also causes extra losses and reduces the overall efficiency.
calculation formula: I
Diode
= 2 x P
out
max
 / U
in min
ad reverse polarity protection for DC input by anti parallel diode
To avoid the power losses a diode is provided with opposite polarity in parallel to the 
input blowing an internal or external fuse if the module is connected to a supply of wrong 
polarity.
calculation formula: I
Diode
= 2 x P
out
max
 / U
in min
au auto-ranging
For standard dual AC input models the range of 115 / 230 V AC is to be selected by 
connecting the input line to different pins on the connector. With auto-ranging the unit 
senses the input voltage and provides automatically the correct connection.
OUTIN
OUTIN
time
delayed
IN OUT
OUT
L
N
1
15V AC
o
r
2
30V AC
OUT
IN










