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Block 27
Block 28
Block 29
Power supply LED
Fan
Consisting of: D10.
Indicates when the power source is correctly powered and
ready for use.
Consisting of: V1.
Powered directly by block 13 (flyback transformer) and cools
the power components.
Undervoltage safeguard
Consisting of: R39, R64, U2B .
If the main supply voltage falls below the minimum allowed
value this safeguard triggers (a tolerance of approx. ±15% of
the power supply voltage is allowed: outside this range the
safeguard triggers).
Block 19
Block 20
Block 21
Block 22
Block 23
Block 24
Adder
Alarm Block
Alarm LED
Current potentiometer
Maximum current adjustment
Power transformer thermostat
Overvoltage safeguard
Consisting of: U2C.
Gathers all the information from block 17 (primary current
reader and limiter), from block 20 (alarms) and from block 22
(current potentiometer), and produces a signal with a suitable
voltage for processing by block 18 (duty cycle maker).
Consisting of: Q3, R43, R44, R38, R36
When an alarm is detected the power source output current is
drastically reduced by making direct adjustments to block 18
(duty cycle maker) and directly changing the reference signal
obtained from block 22 (current potentiometer).
Consisting of: D12.
It is switched on by block 20 (alarms) in the event of:
1) Triggering of thermostatic capsule/thermostat on power
transformer.
Triggering due to undervoltage.
3) Triggering due to overvoltage.
4) Short circuit at output (electrode holder clamp and earth
cable connected to one another or electrode stuck to piece
being welded).
Consisting of: R23.
This is used to set the reference voltage needed to adjust the
output current: when the potentiometer knob is turned the
cursor voltage varies, thus varying the current from the
minimum to the maximum value.
Consisting of: JP1, JP2, JP3.
Used to adjust the maximum cutting current to be supplied by
the power source.
Consisting of: ST1.
When the temperature of the power transformer is too high,
this safeguard is triggered. It is reset automatically after the
alarm condition has ceased.
Consisting of: R1, R5, R14, R19, R24, R29, U2A.
If the main supply voltage exceeds the maximum value this
safeguard triggers (a tolerance of approx. ±15% of the power
supply voltage is allowed: outside this range the safeguard
triggers).
2)
Consisting of: ISO1.
The signal arriving from blocks 24
(power transformer
thermostat) is separated galvanically and sent to block 20
(alarms) for detection of a possible alarm event.
Block 25
Block 26
Galvanic separation
TECNICA 144 - 164
