TroubleshooTing and sysTem TesTs
powermax
65/85
Service Manual 5-5
380/400 V CE 3-phase power supply functional description
AC power enters the system through the power switch (S1) to the input diode bridge (D45). The voltage from the
bridge provides a nominal 530 to 560 VDC bus voltage. The bus supplies voltage and current to the inverter and the
flyback circuit (DC to DC converter) on the power board (PCB3). The power board provides noise suppression and
spike protection. A “soft start” is implemented via the power board resistors (RT4, RT5) and relay (K2).
The inverter consists of a dual IGBT package (Q9), the power transformer, a current sensor, and the control circuit.
The inverter operates as a pulse-width modulated half-bridge circuit driving an isolation transformer. The output of the
isolation transformer is rectified by the output bridge (D44 and D46).
The output circuitry consists of 2 current sensors located on the power board, the pilot arc IGBT (Q10), and the output
choke.
The digital signal processor (PCB2) monitors and regulates the system’s operation and safety circuits. The amperage
adjustment knob on the control board (PCB1) is used to set the output current to the desired value: 20 – 65 amps for
the Powermax65 or 25 – 85 amps for the Powermax85. The system compares the set-point to the output current by
monitoring the current sensors and adjusting the output of the inverter IGBTs. (Q9).
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