X20 system modules • Digital output modules • X20DO2633
1096
X20 system User's Manual 3.10
4.15.6.13 Operation with inductive loads
As inherent to its functional principal, the triac output is cleared when the current crosses zero. Because zero
crossing for current is delayed with inductive loads, it is possible that the triac will be fired again even though it is
not completely cleared at higher output values (between 50 and 100% depending on the inductance of the load).
In this case, a full-wave is output. This causes the available control range (0 to 95%) to be changed.
For open line detection (LowCurrentStatus), a pause in control is required where the triac is not permitted to be
fired. The full wave that is created with inductive loads causes open line detection to be triggered even though
the load on the output is sufficient.
This behavior can be used to detect the full wave and properly adjust the control range (Example: If open line
detection is triggered at a control value of 70%, that means that 0-
70%
corresponds to 0-
100%
output).
Switch-off delay caused by
Inductive load
CfO_SwitchOffValue in %
Zero crossing: Voltage
Zero crossing: Current
Input voltage
Output voltage
Output current
Internal firing signal for the triac
With inductive loads, a suitable varistor must be provided between the output DO x and the phase L (e.g. a varistor
with 275 V
RMS
at 240 VAC).
GND
+24 VDC
GND
+24 VDC
DO
L
N
L
N
Ac
tu
at
or
VDR
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