Instruction manual

NGA 2000 MLT Hardware
INSTALLATION
5 - 34
Emerson Process Management GmbH & Co. OHG
Instruction Manual
90002929
07/2006
WIRING SIGNAL TERMINALS: WIRING INDUCTIVE LOADS
5.5.2 Wiring Inductive Loads
Switching inductive loads is a standard application generating electromagnetic disturbances:
The moment an inductive load (e.g. relay, valve, etc.) is switched off, it‘s magnetic field defies the
change of current flow, generating high voltages (up to hundrets of volts) at the coil‘s contacts. This
impulse reproduces on connected wires and may influence electrical equipment nearby or destroy
signal inputs and/or outputs on electronic boards.
A simple measure helps to avoid such effects:
❏ Shunt a silicon diode to the inductive load‘s contacts shorting the voltage impulse just at it‘s
source.
The diode‘s cathode needs to be connected to the positive side of the coil, the anode to the
negative side (fig. 5-25).
Suitable filter components are available on request for standard valves.
Fig. 5-25: Suppressor Diode for Inductive Loads