Engine Speed Control - Lincoln Electric Classic 300 MP Service Manual

LINCOLN ELECTRIC Classic® 300 MP Service Manual
Figure E.2 – Engine speed control

Engine Speed Control

The ECU monitors the engine speed and during high RPM conditions keeps the engine at a steady 1800
RPM regardless of the welding or auxiliary power loads. If the idle switch is set to the auto position the ECU
will, under no load conditions, regulate the engine speed to 1440 RPM. When at low speed, if at least 100
watts is drawn from either the 120 VAC or 240 VAC receptacles the current transformer will send a signal to
the control board and the control board will signal the ECU to put the engine into high speed.
The control board monitors the voltage across the DC generator brushes and if while at low speed a
welding arc is struck the voltage will drop and the control board will signal the ECU to put the engine into
high speed.
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