Hypertherm MAX200 Service Manual - Manual (Page 46)

MAX200 Service Manual 3-5
MAINTENANCE
Filter Inductor and Chopper Module Diode Circuit
During the off interval of the chopper module output cycle, the magnetic fields of L1 and L2 will collapse, and their
polarity will reverse (looking at page 1 of wiring schematic inductors L1 and L2 will now be negative on their left
side). This action of the inductor will forward bias the chopper output diode causing current flow to pass through it
from bottom to top. L1 and L2 then maintain the cutting arc current flow during the “off” chopper cycle.
Current Sensor Circuit
The current sensor coil CS1 is a magnetic device that produces a voltage when current is sensed from the cable
passing through it. The cable is directly attached to the workpiece, and the sensing of current will occur when the
arc is transferred. This type of sensing phenomena is known as the Hall effect. This voltage is transmitted from pin
3 on PL12, to pin 14 of REC2 on the Control PCB (PCB7).
Shunt Circuit
R1 and R2 are shunt resistors for choppers CH1 and CH2, respectively. R3 carries the sum of the currents flowing
to R1 and R2. The voltage taken across R1 and R2 is sent to Control PCB7. This shunt voltage will be compared
with the current control voltage. Any difference between the two voltages is sensed, and the output control signal to
the chopper module is adjusted to correct any error.