WIKA 851 - Manual (Page 16)

WIKA operating instructions magnetic snap-action contact model 821
GB
16
2003325.03 03/2011 GB/D/F/E
9. Contact protection measures
9.1. Inductive load with DC voltage
With DC voltage the contact protection can be achieved via a free-
wheeling diode, connected in parallel to the load. The polarity of the
diode must be arranged so that it closes when the operating voltage is
on.
Example:
Contact protection
measure with free-
wheeling diode
Contact
Diode
Contact
Contact
9.2. Inductive load with AC voltage
With AC voltage two protection measures are possible:
Example:
Contact protec-
tion measure with
voltage-depend-
ent resistor VDR
Example:
Contact protection
measure with RC
element