Siemens S5-135U/155U appendix Coupling, Mechanisms, Typical Interference Sources at a Glance

Models: S5-135U/155U

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Installation Guidelines

Coupling

Shown in the following table are the four different coupling mechanisms,

Mechanisms and

their causes, and possible interference sources.

Typical

 

Interference

 

Sources at a

 

Glance

 

Coupling Mechanism

Cause

Typical Interference Sources

 

 

SDirect Coupling

Interference

Direct Coupling

Path

Direct or metallic coupling always occurs when two circuits have a common conductor

SSwitched devices (supply affected by inverters and external power supply units)

SMotors being started

SDifferent potentials of component cases with a common power supplys

SStatic discharges

SIMATIC S5

SCapacitive Coupling

Interference

Capacitive Coupling

Path

SIMATIC S5

Capacitive or electrical coupling

S

Interference pickup via

occurs between conductors

 

parallel signal cables

 

which are at different potentials.

S

Static discharge of the

The degree of coupling is

 

operator

proportional to the voltage

S

Contactors

variation as a function of time.

 

 

 

 

 

SInductive Coupling

Interference

Inductive

Coupling Path

Signal

SIMATIC S5

Inductive or magnetic coupling occurs between two conductor loops through which current is flowing. Interference voltages are induced by the magnetic fluxes associated with the currents. The degree of coupling is proportional to the current variation as a function of time.

STransformers, motors, electric welders

SParallel AC supply cables

SCables whose currents are switched¤

SSignal cables with a high frequency

SUnconnected coils

3-4

System Manual

C79000-G8576-C199-06

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Siemens S5-135U/155U appendix Coupling, Mechanisms, Typical Interference Sources at a Glance