Lincoln Electric SVM161-A service manual Figure E.3 Main Igbt Inverter Board

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E-3 THEORY OF OPERATION E-3

FIGURE E.3 - MAIN IGBT INVERTER BOARD

Fan

Superimposition

board

24 VDC

Bus board

AC DC Gate drive signals

Input

HF

board

board

Voltage Feedback

15,+5-+24,+15,48,-

info.reconnect

.ACcktturnon

supplyvolthigh

feedbackvoltage

feedbackcurrent

Current Feedback

Output

IGBT

Diode

Thermostat

Output

Thermostats

Filter bd.

(bypass)

Main IGBT

& Power board

4

_

IGBT's

Output

RF coil

Choke

+

infothermostat

metervoltinput

metercurrentinput

DC blocking

Current

ckt.AConturn

+515,-+15,

infoset

PWMonturn

capacitor board

Input

Hall

Main

Output

Choke

Output

Device

Transformer

board

Transistor

Module

24 VDC Remote 2/4 path (D + E)

HF control signal

888

+48, +24

Control board

Display & LED

board

Control	(D + E)
	Remote 2/4
Knob

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48 VDC

Gas

Solenoid

MAIN IGBT INVERTER BOARD

The filtered input voltage, from the Input Board, is applied through an input choke to the Main IGBT Inverter Board. This input voltage is rectified, regulat- ed and a unity power factor output is developed for the main welding IGBTs. This unity power factor circuit provides several advantages over a traditional bridge rectifier circuit. Among these advantages are that the UPFR operates over a wide range of voltages, there is no need for any manual circuit changes when the input voltages are changed from 115VAC to 230VAC and there is absolute voltage stability maintained on the IGBT electrolytic capacitors. The four main welding IGBTs are located on a large center mounted heat sink assembly.

The pre-charge and auto reconnect circuits are posi- tioned on the Main IGBT Inverter Board. When power is first applied to the V205T the rectified DC input volt- age is applied to the input capacitors through a current limiting circuit. The capacitors are charged slowly and current limited for approximately five seconds. After five seconds a relay closes and the pre-charge circuit is bypassed and a controlled DC input voltage is applied to the weld capacitors and IGBTs making them ready for welding output demands when the IGBTs are gated on. The auto reconnect circuit receives and processes a low-level voltage signal from the Bus Board. This low level signal is utilized to adjust for the

Remote 75, 76, 77 A, B, C

different voltage requirements needed by the weld IGBT circuits. A signal is also sent to the Control Board so that when the input voltage is reduced the output of the machine will be limited accordingly.

The Auxiliary power portion of the board generates several voltages through flyback topology and a 50KHZ switching frequency. These various voltages (+24, +15, +5, +48 and –15) are utilized to operate the control and protection electronics, the gas solenoid, the trigger circuit and the fan motor.

The Main IGBT Inverter Board receives command and pre-set signals from the Control/Display board. It also receives feedback information, both voltage and cur- rent, from the Output Filter Board and Hall Effect Device via the Bus Board. It processes this informa- tion and generates the correct pulse width modulation signal (PWM) that is applied to the gates of the weld IGBTs. This controls and regulates the output of the machine. The thermostats signals are connected to the Main IGBT Inverter Board. This status information is passed on to the Control Board. In the case of an over temperature condition the Control Board will prevent output until the machine cools and the thermostats reset.

Low-level analog signals are generated on the Main IGBT Inverter Board and sent to the Control/Display Board for meter set and actual display values.

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

INVERTEC® V205-T AC/DC™