Lincoln Electric SVM135-B service manual Thermal Protection Over Current, UNDER/OVER Voltage

Return to Section TOC

Return to Section TOC

Return to Section TOC

Return to Section TOC

Return to Master TOC

Return to Master TOC

Return to Master TOC

Return to Master TOC

E-9	THEORY OF OPERATION		E-9
THERMAL PROTECTION		OVER CURRENT
Two normally closed (NC) thermostats pro-		PROTECTION
tect the machine from excessive operating		If the average current exceeds 590 amps,
temperatures. These thermostats are wired
		then the peak current will be limited to 100
in series and are connected to the control
		amps until the average current decreases to
board. One of the thermostats is located on
		under 50 amps.
the heat sink of the output rectifier and the
other is located near the fan. (On later pro-
duction machines this thermostat is located		UNDER/OVER VOLTAGE
on the output choke) Excessive tempera-
		PROTECTION
tures may be caused by a lack of cooling air
or operating the machine beyond its duty
cycle or output rating. If excessive operat-		A protective circuit is included on the
ing temperatures should occur, the ther-		control board to monitor the voltage across
mostats will prevent output from the		the input capacitors.	In the event that a
machine. The yellow thermal light, located		capacitor voltage is too high, or too low, the
on the front of the machine, will be illuminat-		protection circuit will de-energize the input
ed. The thermostats are self-resetting once		contactor. Machine output will be disabled
the machine cools sufficiently. If the ther-		and the “soft start” mode will be repeated.
mostat shutdown was caused by excessive		The protection circuit will prevent output if
output or duty cycle and the fan is operating		any of the following circumstances occur.
normally, the power switch may be left on
and the reset should occur within a 15-		1. Capacitor conditioning is required.
minute period.	If the fan is not turning or	(May be required if machine has been
the air intake louvers are obstructed, then		off for a long period of time and is con-
the power must be removed from the		nected for high input voltage operation.)
machine, and the fan problem or air
obstruction corrected. On later production		2. Voltage across a capacitor exceeds
machines (above code 10500) the cooling		390 volts. (High line surges or improp-
fan runs only when necessary. The F.A.N.		er input voltage connections.)
(fan as needed) system is controlled by the
control board via a solid state relay.		3. Voltage across a capacitor is under 70
		volts. (Due to improper input voltage

connections.)

PROTECTIVE CIRCUITS

4. Internal component damage.

Protective circuits are designed into the Power Wave 455 to sense trouble and shut down the machine before damage occurs to the machine's internal components.

POWER WAVE 455/POWER FEED 10