ESAB Powercut 1600 Service Manual page 78

SECTION 4
4.10.16 Power Board_PCB2 Filter Buss/IgbT Circuit (0558038315)
The Inverter blocks of the PC1600 is where the stored energy in the buss supply (DC power) is converted
to AC and supplied on to the output bridge. Two half bridge inverters are used (allows 230/460 switching)
and the output from them is combined at the secondary of the main transformers (T1-A and T1-B).
Components used:
The Filter Buss capacitors receive power from either the pre-charge of the inrush circuit or from the main
contactor K1. (See the inrush circuit for more detail) Once the bus is fully charged, each of the four filter
caps will have a nominal voltage of 162 VDC across it's terminals. The filter caps then reduce the ripple
on the rectified voltage and supply the filtered bus voltage to the IGBT circuits. Each IGBT circuit (or half-
bridge) will have a nominal buss voltage of 325 VDC, whether configured for 230 VAC input or 460 VAC
input.
4.10
The "buss capacitors" in the PC1600 will maintain a volt-
age charge for approximately 2 minutes after power is
removed from the input of the machine.
The arcing caused by discharging a capacitor into a short-
circuit can cause injury and component damage
To eliminate the voltage from the capacitor, connect the
"bleeder resistor" across the poles of a charged capacitor
and the stored energy will discharge harmlessly through
the resistor. The approximate discharge time is 30 sec-
onds.
When discharged, the cap can be partially tested by using a multimeter set to the ohms scale.
When checking a good capacitor...Connect the + meter lead to the + pole of the capacitor, and
the – lead to the – pole. The meter display will show a number that will change while the leads
are connected, if the meter leads are reversed, the display will change polarity and the value will
change in the opposite direction from the first test.
2- twin IGBT transistors, Q101 and Q102
4-Electrolytic Capacitors, C37, C40, C44 and C47
2- Main transformers T1-A and T1-B
Capacitor Information
Serious Shock Possible
DESCRIPTION Of OPERATION
78