Chapter 4
– Further Notes
4-1
Chapter 4
– Further Notes
Influence of ground fault monitoring devices
In the line filter, capacitors are placed between the phases and ground, which can cause larger
charge currents to flow to ground when the filter is first switched on. The amount of this flow has
already been minimized by constructional circuit details. Nevertheless, ground fault monitoring
devices possibly present may be triggered. Ground currents with high-frequency components and
DC components may also flow under normal operating conditions. If faults occur, large DC-
carrying ground currents may flow, possibly preventing the ground fault monitoring device from
responding. For this reason, the use of ground fault monitoring devices is not recommended.
But should they be prescribed in certain applications for safety reasons, you should choose
monitoring devices which are suited for DC, AC and HF ground currents. In addition, you should
ensure that their responsiveness and time characteristics are adjustable, so that a disturbance is not
immediately caused the first time the frequency inverter is switched on.
Components susceptible to interference
The following components must be classified as particularly susceptible to interference from
electromagnetic fields. Special attention should therefore be paid to them during installation
:
Sensors with analog output voltages (< 1 volt)
Load cells
Tractive force meters
Torque measuring hubs
Resistance thermometer PT100
Thermoelements
Anemometers
Piezoelectric sensors
AM radios (only long and medium wave)
Video cameras and TV sets
Office PCs
Capacitive proximity switches and filling level sensors
Inductive proximity switches and metal detectors
Ripple control transmitters, baby talkers, etc., i.e. all communication devices which use low-
voltage systems as transmission medium
Devices which do not comply with the pertinent EMC requirements
