ESAB Aristotig 405 AC/DC, Service Manual

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A1-6 DC-OUTPUT VOLTAGE BUFFER AND OVERVOLTAGE PROTECTION
Two separate cables convey the output voltages to connectors X9-1 and X9-3. The safety circuit
16 monitors whether an excessive positive, an excessive negative, or an excessive AC voltage is
applied to the output. If any of these cases occurs, a memory signal 5 is set. It switches off the
complete inverter supply.
Cf. GENERAL DESCRIPTION, 4 Protection against Excessive Output Voltage.
A1-7 PRIMARY MOSFET DRIVER
Warning! The circuit and its parts are connected to mains voltage potential.
The Figure only shows the Low side; the High side is controlled in a similar way.
The PWM clock signal is sent from A8 to A1. A1 causes potential isolation 14 and amplifies the
control signal for the MOSFETs (A5, A12, A4, A11). In the event of a MOSFET defect, also per-
form a function test for the driver stage A1-7 after repair on A5, A12, A4, A11 is complete. The
suppressor diode (a) protects the MOSFET inputs from high voltages, and the driver stages from
pulse overload in case of faulty MOSFETs. The resistor (b) provides 1 k
Ω
for each MOSFET
group. The gate series resistors (c) have a value of 8.2
Ω
for each MOSFET.
a1-6.pcx
a1-7.pcx