I have a data sheet that gives the coil pickup voltage as "0.85…1.1 x Us] and coil dropout voltage as "0.3…0.6 x Us".

I am assuming that Us refers to the nominal or specified coil voltage, but why is it "Us"?


  • 1
    \$\begingroup\$ U is commonly used as as symbol for voltage on German schematics ... what make is the contactor? \$\endgroup\$
    – user16324
    Commented May 29, 2015 at 20:34
  • \$\begingroup\$ @BrianDrummond Here is a Siemens contactor spec. It uses exactly that nomenclature. \$\endgroup\$ Commented May 29, 2015 at 20:39
  • \$\begingroup\$ The data sheet I have is from Rockwell (Allen-Bradley). \$\endgroup\$
    – frog_jr
    Commented May 29, 2015 at 20:58

1 Answer 1


Subscript S in \$U_S\$ symbol stands for German word die Spule which means the coil. So \$U_S\$ is the coil voltage.


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