How the Plasma Power Supply Operates
Powermax65/85/105 SYNC Troubleshooting Guide 810430 169
Theory of operation
Powermax65/85 SYNC
200 V – 600 V CSA 1-phase or 3-phase functional description
AC power goes into 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 supplies
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 PCB (PCB3). The power PCB provides noise
suppression and spike protection. The power PCB resistors (RT4, RT5) and relays (K2, K3) do a
“soft start.”
The PFC boost converter has an insulated gate bipolar transistor (Q11), PFC choke, and control
circuit. It supplies a 760 VDC bus voltage when the input AC voltage is between 200 VAC and 540
VAC. At 600 VAC, the nominal bus voltage is 840 VDC.
The inverter has 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 bridge (D48 and D51) corrects the output of the isolation
transformer.
The output circuitry has 2 current sensors located on the power PCB, the pilot arc IGBT (Q13), and
the output choke.
The digital signal processor (PCB2) monitors and controls the system’s operation and safety
circuits. The amperage adjustment knob on the control PCB (PCB1) is used to set the output
current: 20 A – 65 A for the Powermax65 SYNC or 25 A – 85 A for the Powermax85 SYNC. The
system compares the setpoint to the output current by monitoring the current sensors and adjusting
the output of the inverter IGBTs (Q12).
380 V CCC / 400 V CE 3-phase functional description
AC power goes into the system through the power switch (S1) to the input diode bridge (D45). The
voltage from the bridge supplies a nominal 530 VDC 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 PCB
(PCB3). The power PCB provides noise suppression and spike protection. The power PCB
resistors (RT4, RT5) and relay (K2) do a “soft start.”
The inverter has 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 bridge (D44 and D46) corrects the output of the isolation transformer.
The output circuitry has 2 current sensors located on the power PCB, the pilot arc IGBT (Q10), and
the output choke.
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