Hypertherm Powermax30 Service Manual - Manual (Page 42)

MAINTENANCE
powermax30
Service Manual 3-3
Theory of operation
General
Refer to the Functional description and Sequence of operation sections below, and to Section 5, Wiring diagrams.
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 2 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 amps
adjustment knob is used to set the output current to the desired value between 15 and 30 amps. 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).