Hypertherm Powermax1650 Service Manual - Manual (Page 30)

Theory of Operation
General
Refer to Functional Description, Sequence of Operation and the system wiring diagram in Section 6.
Functional Description
AC power enters the system through the power switch S1 to the input diode bridge D24. The voltage from the diode
bridge supplies the Power Factor Correction (PFC) Boost Converter which provides a 750 VDC bus voltage. The
bus voltage then supplies the inverter and the flyback system 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 isolated gate bipolar transistor (IGBT) Q14, choke and control circuit. It provides
a 750 VDC bus voltage when input AC voltage is between 170 and 540 VAC. When the input voltage is above 540 VAC
the bus voltage will rise to Vin* 2.
The inverter consists of an IGBT Q13, the power transformer T2, a current sense transformer, and sections of the
power board. The inverter operates as a pulse-width, modulator-controlled bridge circuit, and is rectified by the
output diode.
The output circuitry consists of 2 current transfer sensors located on the power board, the pilot arc IGBT Q15 and
the output choke.
The control board’s microprocessor monitors and regulates system operation and safety circuits. The current is set
to the desired value by adjusting the current adjustment knob. 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 Q13.
The control board PCB3 includes a pilot arc control switch, allowing the operator to turn the pilot arc ON (useful
when cutting expanded metal), OFF (for maximum life of consumables), or increase the pilot arc to 30A (useful for
gouging or non-transferred-arc cutting).
MAINTENANCE
powermax1650 Service Manual
3-3
0