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ANALYSIS OF THE BLOCK DIAGRAM
NOTE:
Unless indicated otherwise, it should be assumed that
the components are assembled on the power board.
Consisting of: C1, T4, C8, C15.
Prevents noise from the machine from being transmitted along
the main power line and vice versa.
Consisting of: PD1, R4.
Prevents the formation of high transitory currents that could
damage the main power switch, the rectifier bridge and the
electrolytic capacitors.
When the power source is switched on the relay PD1 is de-
energised, capacitors C21, C22, C27 are then charged by R4.
When the capacitors are charged the relay is energised.
Consisting of: PD1.
Converts the mains alternating voltage into continuous pulsed
voltage.
Consisting of: C21, C22, C27.
Converts the pulsed voltage from the rectifier bridge into
continuous voltage.
Consisting of: Q5, Q8.
Converts the continuous voltage from the filter into a high
frequency square wave capable of piloting the power
transformer.
Regulates the power according to the required welding
current/voltage.
Consisting of: T2.
The C.T. is used to measure the current circulating in the
power transformer primary and transmit the information to
block 17 (primary current reader and limiter).
Consisting of: T3.
Adjusts the voltage and current to values required for the
welding procedure. Also forms galvanic separation of the
primary from the secondary (welding circuit from the power
supply line).
Consisting of: D32, D33, D34 .
D34 converts the current circulating in the transformer to a
single direction, preventing saturation of the nucleus.
D32, D33 recirculate the inductance output current (block 9)
when the IGBT's are not conducting, bypassing the power
transformer (block 7).
Block 1
Block 2
Block 3
Block 4
Block 5
Block 6
Block 7
Block 8
EMC Filter
Pre-charge
Rectifier bridge
Filter
Chopper
Current transformer
Power transformer
Secondary diodes
Block 9
Block 10
Block 17
Block 18
Inductance
Secondary EMC Filter
Primary current reader and limiter
Duty cycle maker
Consisting of: L1.
Levels the secondary board diodes’ output current making it
practically continuous.
Consisting of: C28, C33.
Prevents noise from the power source from being transmitted
through the welding cables and vice versa.
Consisting of: D2, R25.
Reads the signal from block 6 (current transformer) and scales
it down so it can be processed and compared in blocks 18 and
19.
Consisting of: U1.
Processes the information from block 19 (adder) and block 17
(primary current reader and limiter) and produces a square
wave with variable duty cycle limiting the primary current to a
maximum pre-set value under all circumstances.
Block 11
Block 12
Block 13
Block 14
Block 15
Block 16
Voltage rectifier
Auxiliary power supply trigger
Auxiliary power supply
Driver
Separator transformer
Transformer Pilot
Consisting of: D11,C18.
Rectifies and filters the voltage from the tertiary winding of the
power transformer (block 7).
Consisting of: R18, R35, C20.
Via the resistors, the power source supplies the necessary
voltage to power block 13 (power supply).
Consisting of: U3, C17.
Stabilises the voltage at 12Vdc for the power arriving from
block 12 (auxiliary power supply trigger) and from block 11
(voltage rectifier).
Consisting of: Q6, D19, D23, Q7, D27, D26
Picks up the signal arriving from block 15 (separator
transformer) and under the control of block 17 (transformer
pilot) adjusts it to suit piloting of block 5 (chopper).
Consisting of: T1.
Supplies two signals, which are separated galvanically from
one another, that will be sent to power block 14 (driver).
Consisting of: Q4, D20, D22, D24.
Amplifies the signal arriving from block 18 (duty cycle maker),
needed to pilot block 15 (separator transformer).
TECNICA 144 - 164
