Monitoring The Dcs880 Power Section; Thermal Overload And Short-Circuit Protection; Mains Cable (Ac Line Cable) Short-Circuit Protection - ABB DCS880 H1 Hardware Manual

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Monitoring the DCS880 power section

The power part of converters size H1 ... H6 is monitored by means of a galvanic isolated PTC
thermistor. The PTC is installed on the heat sink in an isolated configuration. The PTC's resistance
and protective effect correspond to the maximum temperature defined by the type code.
The air entry temperature at the power part of converters size H7 and H8 is monitored by means of a
galvanic isolated PTC thermistor. The sensor measures the power part's radiated heat and any
changes in the cooling air temperature and volume.
The PTC's resistance change is proportional to the temperature. It is read and evaluated in the
drive's firmware. If the temperature increases above the preset value, then first a warning and - if the
temperature continues to rise - a fault message is generated. The preset value must not be set more
than 5 degrees above the permissible ambient temperature.
For converter size H7 and H8 the cooling air volume can only be detected indirectly. Thus,
additionally a differential-pressure switch has been installed at the unit's housing. It is always located
close to the power terminals.
The differential-pressure switch compares the pressure inside the drive with the normal air pressure.
If the fan is switched on, the drive's door is closed, no covers have been removed and the pressure
switch signals 'cooling conditions ok' it is possible to release the converter. There is no need to set a
specific differential pressure (recommendation: use the center setting). The differential pressure
switch should be connected to the converter fan acknowledge signal.

Thermal overload and short-circuit protection

The drive protects itself and the input and motor cables against thermal overload when the cables are
dimensioned according to the nominal current of the drive.

Mains cable (AC line cable) short-circuit protection

Always protect the input cable with fuses. Size the fuses according to local safety regulations,
appropriate input voltage and the rated current of the drive (see chapter
Technical data).
High-speed semiconductor fuses provide short-circuit protection, but don't provide thermal overload
protection.
Planning the electrical installation
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