Lincoln Electric 355M, 405M service manual 1TABLE of CONTENTS-THEORY of Operation Section E-1

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E-1TABLE OF CONTENTS-THEORY OF OPERATION SECTION E-1

Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .E-1

General Description	E-2
Input Line Voltage, Auxiliary Transformer and Precharge	E-2
Switch Board and Main Transformer	E-3
DC Bus Board, Power board and Control Board	E-4
Output Rectifier and Choke	E-5
Thermal Protection	E-6
Protective Circuits	E-6
Over current Protection	E-6
Under/Over Voltage Protection	E-6
Insulated Gate Bipolar Transistor (IGBT) Operation	E-7
Pulse Width Modulation	E-8
Minimum/Maximum Output	E-8
FIGURE E.1 BLOCK LOGIC DIAGRAM

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		Main Switch Board
Input switch	Input	Primary
	Rectifier
		Current
		Sensor
		Reconnect
		Switch
		Primary
		Current
		Sensor
		Fan

		115VAC Fan Supply			Primary Current Feedback(2)			I
				lntroCoFan	Input Relay Control			GBTDriveSigna
		Auxiliary			Soft Start Control
220 VAC Transformer					V/F Capacitor Feedback (2)
								l
		40VDC	Machine Control Supply
			+15VDC, -15VDC, +5VDC
		Power
		Board	RS232 Supply +5VDC					Control Board
220	42VAC
			Can Supply +5VDC
Receptacle	65VAC
		DC			Arc		Electrode
		Bus			Link	Wire	Sense
		Board	40VDC
						Feeder
						Recp.		Thermostats
								2

To

Feeder

POWER WAVE 355M/405M

To Control

Board

FeedCurre backnt

Choke

seen

ltoV Sage

O ututp

21 Lead

Voltage

Sense

Recp.

Positive

Output

Terminal

Negative

Output

Terminal

Yellow

Thermal

LED

Status

Red/Green

LED

R232

Connector