Hypertherm Powermax65 Service Manual Rev.1 - Manual (Page 130)

TroubleshooTing and sysTem TesTs
5-4
powermax
65/85 Service Manual
Theory of operation
General
Refer to “Sequence of operation” below and Section 8, Wiring diagrams.
200 – 600 V CSA 1- or 3-phase power supply functional description
AC power enters the system through the power switch (S1) to the input diode bridge (D50). The voltage from the
bridge supplies the power factor correction (PFC) boost converter, which provides a nominal 760 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 relays (K2, K3).
The PFC boost converter consists of an insulated gate bipolar transistor (IGBT Q11), PFC choke, and control circuit. It
provides a 760 VDC bus voltage when the input AC voltage is between 200 and 540 VAC. At 600 VAC, the nominal
bus voltage is 840 VDC.
The inverter consists of a dual IGBT package (Q12), the power transformer, an output 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 (D48 and D51).
The output circuitry consists of 2 current sensors located on the power board, the pilot arc IGBT (Q13), 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 (Q12).