KUHNKE Automation
37
7.5.4
Half sine wave control
Half sine wave control is intended to separately control each of multiple con-
tinuously operated IR lamps. After the soft start stage, the thermo-controller
automatically sets itself to the specified heat output.
As opposed to phase-fired control, half sine wave control is based on com-
plete half-cycles. Interconnecting 3 output channels allows complete sine
waves to be picked off the mains, thereby substantially reducing harmonic
perturbations of the electrical power mains.
Load power variation between 0...100% in steps of 1%.
7.5.5 Mains Voltage Correction
In order to accurately adjust the heat output, the controller verifies the supply
voltage of each of the phases and automatically adapts the setpoint heat
output to each change in voltage. Parameter "
NominalVoltage
" is available
to set the "nominal voltage".
The phase-to-phase voltage is computed from the phase voltages measured
separately.
Several cycles are measured to obtain an average phase-to-phase voltage
which is then compared to the value computed previously. Where the aver-
age voltage differs by more than 3V from the voltage determined before,
each channel's heating power will be computed again and the control values
of all channels adapted to the mains voltage.
The control value set for every channel is sent to the control unit as "
Actu-
alControlValue
" for verification.
System constraints do not allow mains voltage correction to obtain control
values above 100%. This particularly applies to high control values at low
mains voltages.
If the thermo-controller fails to correct the mains voltage, channel state bit 12
"power correction error" of the affected channels will be set.
