6
THC1
for more information
05
04
The design of the automatic torch height control system using THC1 set differs from other
similar systems. In addition to standard «Torch UP” and «Torch Down» signals, the THC1
transmits the effective arc voltage signal over Ethernet. The PLCM series CNC controller
received this information, adjusts the torch height and then sends the current adjustment
status to the CNC system (PUMOTIX, MACH3, etc.). It allows to eliminate any Z axis auto-
oscillations, as the PLCM knows not only the required adjustment direction, but also the
overrange value from which the required Z axis offset at a time can be determined. During
«classical» control carried out using «Torch UP» and «Torch Down» signals without PLCM
controller some Z axis oscillations may occur. It will affect the cutting quality adversely. In
addition to the main measurement function the THC1 set controls torch firing process and
transmits the current ARC OK signal status to the PLCM. The torch firing process is monitored
by the classical ARC OK signal and the current transformer. The ARC OK input is galvanically
isolated from optocoupler. The plasma source switches it by means of a relay. The CT (current
transformer) input is used if the plasma source is not equipped with a torch firing process
monitoring circuit. A current transformer (100А:5А) inductively coupled with plasma source
power supply phase conductor is connected to this input (see the connection diagram).
Almost all currently known plasma systems provide an interface for connecting a sensor for
measuring current arc voltage. Some of them provide with a low voltage signal with a division
ratio.
Such a method of connection to the plasma system is preferable, as the output voltage is
safe for human and imposes lower requirements to insulation, which allows arranging a more
convenient connection of THC sensor (LV input). If the integrated plasma system voltage divider
is unavailable, then THC sensor can be connected directly to special terminals inside plasma
system (HV input).
The available ТНС sensor connection methods shall be described in a plasma system
operation manual. The choice of a connection input depends on a plasma system in use. The
measurement circuit inside the divider module THC1-DV1 is switched using Control switch
(see part 6. Outputs, display and connection purpose).
Operating principle
5
5
Differences between LV and HV
inputs of THC1-DV1 module
4
4
