Service manual

Edition 101222
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s1Cad160
DESCRIPTION OF OPERATION
Caddyr Mig C160i is a set of following modules:
S power PCB -- AP1
S control PCB -- AP2
S MMC panel -- AP3
S gas valve -- K1
S wire feeding motor -- M2
S fan -- M1.
The power PCB contains all the track of energy conversion. It is supplied from the 230V
50/60Hz mains. There is the EMI filter on the input, then half--controlled thyristor bridge.
Thyristor are not fired until DC bus capacitors are not charged via pre--charge circuit.
Between the rectifier and the DC bus capacitors the boost converter is placed. It contains
the high frequency inductor, the switch (MOSFET) and the diode. Control system of the
boost converter is placed on the control PCB (AP2). The switch in boost converter control
provides: a) sinusoidal shape of the input mains current, b) stabilised voltage on the DC
bus.
By the principle, the voltage is higher the amplitude value of the AC input voltage. In the
CaddyMigs it is 390...400V. The boost converter’s frequency is 70 kHz. The converter that
provides the power to welding has two switch forward topology. The switching frequency is
70 kHz. By the principle, the maximum converter’s duty cycle is less then 50%. Transformer
ratio is 5,5:1, what means that peak voltage in secondary winding of the power transformer
is about 70V. The high frequency rectifier + inductor are connected to the transformer’s
secondary winding. The control circuits of the forward converter are included in the control
PCB.
Beyond the both converters control circuits the control PCB contains also the rest of needed
circuits. On the primary side it includes voltage supervisor, auxiliary power supply, primary
circuits overheating and overvoltage protection. On the secondary side there are: process
sequence and control, short arc control, overheating protection, wire feed speed regulator,
and gas valve controller.