Lincoln Electric SVM158-A service manual Switch Board Main Transformer

Return to Section TOC

Return to Section TOC

Return to Master TOC

Return to Master TOC

E-3		THEORY OF OPERATION							E-3
	FIGURE E.3 – SWITCH BOARD & MAIN TRANSFORMER
			Main Switch Board					To Control
								Board	urrentC
								Feedback
	Input								Positive
Input switch				Primary					Output
	Rectifier								Terminal
				Current
				Sensor
		Reconnect						Choke	Negative
									Output
		Switch							Terminal
				Primary				Sense
				Current
				Sensor
		Fan	ControlFan				IGBTDriveSignal	VoltageOutput
24VAC		115VAC Fan Supply		Primary Current Feedback
				Input Relay Control
Auxiliary				Soft Start Control
115VAC, 42VAC Transformer				V/F Capacitor Feedback (2)
		Machine Control Supply
		+15VDC, -15VDC, +5VDC
		Power
28VAC		Board SPI Supply +15VDC +5VDC					Control Board
	40VDC
14 Pin		RS232 Supply +5VDC
									RS232
Amphenol
				SPI Communications				& +15VDC, +5VDC Supply
		Remote Control & Trigger Remote				Mode		Advanced
						Panel		Display	Process
				Board				Panel
						(Not used if APP			Panel
						is in place)
6 Pin				12
				VDC
Amphenol
			Output	Weld	Optional Solenoid
			Control	Terminals

Output

Potentiometer

Return to Section TOC

to Section TOC

Return to Master TOC

to Master TOC

SWITCH BOARD &

MAIN TRANSFORMER

There is one switch board in the Invertec V350-Pro. This board incorporates two pairs of input capacitors, two insulated gate bipolar transistor (IGBT) switching circuits, a fan motor drive circuit, and a voltage/fre- quency capacitor feedback circuit. The two capaci- tors in a pair are always in series with each other. When the reconnect switch is in the lower voltage position the capacitor pairs are in parallel . Thus two series capacitors in parallel with two series capacitors. When the reconnect switch is in the high voltage posi- tion the two capacitor pairs are in series. Thus four capacitors in series. This is required to accommodate the higher input voltages.

When the input capacitors are fully charged they act as power supplies for the IGBT switching circuits. When welding output is required the Insulated Gate Bipolar Transistors switch the DC power from the input capacitors, "on and off" thus supplying a pulsed DC current to the main transformer primary windings. See IGBT Operation Discussion and Diagrams in this section. Each IGBT switching circuit feeds current to a separate, oppositely wound primary winding in the

main transformer. The reverse directions of current flow through the main transformer primaries and the offset timing of the IGBT switching circuits induce an AC square wave output signal at the secondary of the main transformer. The two current transformers (CT) located on the switch board monitor these primary currents. If the primary currents become abnormally high the control board will shut off the IGBTs, thus dis- abling the machine output. The DC current flow through each primary winding is clamped back to each respective input capacitor when the IGBTs are turned off. This is needed due to the inductance of the transformer primary winding. The firing of the two switch boards occurs during halves of a 50 microsec- ond interval, creating a constant 20 KHZ output. In some low open circuit Tig modes the firing frequency is reduced to 5KHZ.

The Invertec V350-Pro has a F.A.N. fan as needed cir- cuit. The fan operates when the welding output ter- minals are energized or when a thermal over tempera- ture condition exists. Once the fan is activated it will remain on for a minimum of five minutes. The fan dri- ver circuit is housed on the switch board but it is acti- vated from a control board signal.

Return

Return

NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.

V350-PRO