Hobart Welding Products TM-944C manual Theory of Operation

SECTION 5 − THEORY OF OPERATION

1 Circuit Breaker CB1

Protects unit from an over-current condition by opening primary power line.

2 Power Switch S1

Turns unit and fan motor FM on and off.

3Fan Motor FM And Transformer

Controlled by power switch S1. Fan cools internal components, and transformer supplies control voltage to PC1.

4 Thermostat TP1

If unit overheats, TP1 opens stopping all weld output.

5 Gun Trigger Receptacle RC3

Connects gun trigger circuit to welding power source.

6 Control Board PC1

Controls weld output by connecting primary power to main transformer T1 through a board-mounted contactor that is activated by pressing the gun trigger. PC1 also regulates wire feed motor speed with a motor control circuit. Speed is set by feedback from Wire Feed Speed Control R1.

7 Gas Valve GS1

Controls shielding gas flow. Pressing gun trigger opens valve.

8 Wire Speed Control R1

Controls wire feed motor speed by providing a reference voltage to motor control circuit on PC1.

9 Range Switch S2

Allows selection of weld output voltage.

10 Main Transformer T1

Supplies power to weld output circuit.

11 Main Rectifier SR1

Changes the ac output from T1 to full-wave rectified dc output.

12 Output Capacitor C1

Smooths dc weld voltage from main rectifier SR1.

13 Stabilizer L1

Smooths dc weld current from main rectifier SR1.

14 Polarity Changeover Block

Terminals allow changing between DCEP and DCEN processes.

15 Wire Drive Motor

Feeds wire at a speed set by R1. Pressing gun trigger activates wire drive motor.

3	4	5
Fan Motor FM	Thermostat	Gun Trigger
And Transformer	TP1	Receptacle RC3

2

Power Switch

S1

		6
	1	Control Board
		PC1
	Circuit
Line	Breaker CB1
L1
	Single-Phase
	Line Input
	Power
Neutral Line
(115 VAC Model)
	Line L2
(230 VAC Models)

7

Gas Valve

GS1

8

Wire Speed

Control R1

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