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5 Commissioning
5.2 Setting the base load
34
A base load can be set, in addition to the analog current input and the potenti-
ometer input. Since these input signals are added together, the input signal
gain must be corrected by adjusting the "full wave" trimmer (7).
For instance, if a heating system is to be operated with a 33% base load, with
the other 66% of the output being regulated by the controller, then the proce-
dure is as follows:
Calculate the reduction factor of the controller signals.
In this example it would be 100% : 66% = 1.5.
Multiply this factor by the intended base load setting.
In this case: 1.5 x 33% = 50%.
The factor 0.5 means that the external potentiometer must be set to 50% of
the full-scale value.
Adjustment:
h Set the potentiometer to the calculated fraction of the full scale (e.g. 50%)
h Apply the maximum current (e.g. 20mA) to the current input
h Turn the "full wave" trimmer clockwise or counter-clockwise until the green
LED for "full wave" just light up in phase-angle control, and does not light
up in burst-firing mode.
Power units 05.01
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