Main Transformer, Output Board And Torch Connector - Lincoln Electric Tomahawk 1500 Service Manual

LINCOLN ELECTRIC Tomahawk® 1500 Service Manual
Figure E.3 – Main transformer, output board and torch connector

Main Transformer, Output Board and Torch Connector

The 400 volt pulsed DC output of the full wave bridge inverter (located on the inverter board) is coupled to
the primary winding of the main transformer. Each IGBT pair on the inverter board acts as a switch
assembly. Each switch assembly drives current through the primary winding of main transformer. When
the first IGBT pair is on (driving current in one direction) the other IGBT pair is off. When the first IGBT pair
is off the second IGBT pair turns on driving primary current in the opposite direction. Thus, the main
transformer is receiving AC current in the primary winding.
The secondary winding of the main transformer is coupled to the output board. The output of the
secondary winding is a 270 VAC square wave at 20 KHz.
All of the outputs (both pilot and cutting) go through the output board. The function of this board is to
manage the output currents and signals. Two diode modules configured as a full wave bridge, rectify the
secondary AC output of the main transformer to create the DC output. Two current sensors monitor the
current that flows through the work piece and the torch electrode. This feedback information is sent to the
input board. The output board also receives the parts-in-place and trigger information from the torch
connector. This information is passed onto the input board. The pilot arc (18 amps for 4 seconds) is
managed by an IBGT switch located on the output board.
The output choke, that is in series with both the pilot circuit and the cutting circuit, provides current
filtering to enhance arc stability.
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