Hypertherm Powermax30 XP Service Manual - Manual (Page 55)

Powermax30 XP Service Manual 808150 Revision 1 55
Section 5
Troubleshooting and System Tests
Theory of operation
Functional description
AC power enters the system through the power switch (S1) to the input diode bridges (D24, D30). The voltage from the
diode bridge supplies the power factor correction (PFC) boost converter, which provides a nominal 375 VDC bus
voltage. The bus voltage then supplies voltage and current to the inverter and the flyback circuit power supply (DC to DC
converter) on the power board (PCB2). The power board provides noise suppression and spike protection. A “soft start”
is implemented via the power board resistor and relay (K1).
The PFC boost converter consists of an insulated gate bipolar transistor (IGBT Q1), choke, and control circuit. It
provides a 375 VDC bus voltage when the input AC voltage is between 120 and 240 VAC.
The inverter consists of an IGBT (Q2), the power transformer, a current-sense transformer, and sections of the power
board. The inverter operates as a pulse-width, modulator-controlled bridge circuit that is rectified by the output
diode (D27).
The output circuitry consists of two current sensors located on the power board, the pilot arc IGBT (inside the
D27 module), and the output choke.
The control board’s microprocessor monitors and regulates the system’s operation and safety circuits. The amperage
adjustment knob sets the output current to the desired value between 15 A and 30 A. The system compares the
set-point to the output current by monitoring the current sensor and adjusting the pulse-width output of the inverter
IGBT (Q2).