MAIN TRANSFORMER
The pair of IGBTs act as a switch assembly. This
assembly feeds a primary winding of the main trans-
former. When current is pulsed through this primary
winding, a resultant current is produced on the sec-
ondary winding of the main transformer. The DC cur-
rent flow through the primary winding is redirected or
“clamped” back to the filter capacitors when the IGBTs
are turned off. This is needed due to the inductance of
the transformer primary winding.
The primary current also passes through the current
transformer, which sends a signal to the control cir-
cuits of the inverter board. This signal and the control
circuits limit the maximum primary current flow
through the IGBTs. The pair of IGBT’s are fired at 15
microsecond intervals, creating a constant 66.6KHz
output.
The secondary portion of the main transformer is made
up of one winding. This winding supplies the
electrode-to-nozzle and electrode-to-work voltages
and the resulting currents. This high current winding is
capable of supplying maximum output current during
the cutting process. The output current is regulated
via pulse width modulation. The control circuitry, on
the inverter board, receives a signal from the control
board and regulates the output current to the desired
level.
