ESAB Origo Feed 304 M12 Series, Service Manual

Page: 26 / 40

DESCRIPTION OF OPERATION
0740 800 144 - 26 - © ESAB AB 2018
13AP1:9 Motor driving / braking
The motor is powered by the sm60 V supply. Pulse width modulation, controlled by
transistor Qd, is used to vary the motor voltage. The pulse frequency is 39 kHz, the old
version of the board has a pulse frequency of 12 kHz. The maximum conducting time of the
pulses is 99% of the pulse cycle time. Free-wheel diode D11 maintains motor current during
the pulse breaks.
Feed 304: At a drive roller speed of 273 r/min, the wire feed speed is 25 m/min.
Feed 484: At a drive roller speed of 166 r/min, the wire feed speed is 25 m/min.
If the wire speed deviates from the set value by more than 1.5 m/min for more than 5 s, wire
feed will be stopped. From circuit board, print no. 487165-003 (see
"13AP1 Component
positions" , page 32), the maximum speed deviation is ±0.9 m/min.
Pins D and E in the remote control unit connector 13XS13 provide power for the motor in an
intermediate wire feed unit or for a PKE (push/pull) welding torch. If an intermediate wire feed
unit is being used in extreme applications (low mains voltage and long cables), an additional
4700 µF smoothing capacitor 13CXX must be connected (ordering number 0193 141 048).
Current limit
The voltage drop across resistor R92 provides a signal that is proportional to the motor
current. When the current exceeds the current limit, IC6:2 turns off the gate pulse to Qd.
When the current drops, Qd conducts again at the next gate pulse. The first version of the
control board (0486 205 886) has a fixed current limit at 15.4 A. The current limit is related to
the pulse peak current.
The new version of the control board (0487 166 8xx) has a dynamic current limit controlled
by the processor.
Feed 304: The current limit is 20 A on starting. When the set speed is achieved, this is
reduced to 13 A.
Feed 484: The current limit is 20 A on starting. When the set speed is achieved, this is
reduced to 15 A.