Appendix
116 Operating instructions RLD
ELTROPLAN
-
REVCON
Elektrotechnische Anlagen GmbH
3. The quality of the mains voltage is visibly reduced by commutation breakdowns, which
are caused by e.g. neighbouring I-inverters. As the value of the feedback current is mainly
determined by the difference between the actual values of DC-bus voltage and mains volt-
age this current increases rapidly caused by the commutation breakdown of the mains volt-
age. Possibly this leads (without current control) to an overcurrent tripping of the power
feedback unit. With current control this tripping is prohibited reliable.
All three events have the same result on the reaction of the power feedback unit: As soon
as the current control is in action, the DC-bus voltage increases from its prior value up to
the tripping value (DC-bus overvoltage) of the controller. Together with the DC-bus volt-
age the switching frequency of the power feedback unit increases from 150 Hz in standard
operation up to 10 kHz.
In this operational mode the switching losses of the IGBT’s increase rapidly. This heat
cannot be transmitted from the active zone of the semiconductor to the heat sink fast
enough and therefore a continuous operation in this mode is not possible. To protect the
IGBT’s nevertheless, the current control is superimposed by an I²t-control, which measures
the height of the switching frequency (mark for the current) and its duration and which
stops the power feedback unit before a critical state is reached. This means, that depending
on duration and height of the overload situation a tripping of the power feedback unit oc-
curs.
3.
Option IL (Isolating lacquer)
To protect the electronic components of the power feedback unit from pollution of the
cooling air, all printed circuit boards may be coated with an isolating lacquer. This option
improves the service reliability, but it doesn’t release the user from the duty to observe the
in chapter 3.2 specified application conditions.
Содержание RLD B
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