Lincoln Electric IM924 manual Negative Electrode Polarity, Voltage Sensing

A-4 INSTALLATION A-4

CABLE INDUCTANCE, AND ITS EFFECTS ON PULSE WELDING

For Pulse Welding processes, cable inductance will cause the welding performance to degrade. For the total welding loop length less than 15.24m (50 ft.), traditional welding cables may be used without any effects on welding performance. For the total welding loop length greater than 15.24m (50 ft.), the K1796 Coaxial Welding Cables are recommended. The weld- ing loop length is defined as the total of electrode cable length

(A)+ work cable length (B) + work length (C) (See Figure A.3).

FIGURE A.3

POWER
WAVE	A

C

WORK

B

For long work piece lengths, a sliding work connection should be considered to keep the total welding loop length less than 50 feet. (See Figure A.4.)

FIGURE A.4

POWER	A		A
WAVE
	C	WORK	C

B	B
SLIDING WORK CONNECTION

K1796 COAXIAL CABLE

MEASURE FROM END

OF OUTER JACKET OF

CABLE

Output connections on some Power Waves are made via 1/2- 13 threaded output studs located beneath the spring loaded output cover at the bottom of the case front.

Most welding applications run with the electrode being posi- tive (+). For those applications, connect the electrode cable between the wire feeder and the positive (+) output stud on the power source (located beneath the spring loaded output cover near the bottom of the case front). Connect the other end of the electrode cable to the wire drive feed plate. The electrode cable lug must be against the feed plate. Be sure the connection to the feed plate makes tight metal-to-metal electrical contact. The electrode cable should be sized according to the specifications given in the work cable con- nections section. Connect a work lead from the negative (-) power source output stud to the work piece. The work piece connection must be firm and secure, especially if pulse weld- ing is planned.

When welding with the STT process, use the positive output connection labeled “STT” for STT welding. (If desired ,other welding modes can be used on this stud; however, the aver- age output current will be limited to 325 amps.) For non-STT processes, use the positive output connection labeled “Power Wave”, so that the full output range of the machine is avail- able.

Do Not connect the STT and Power Wave stud together. Paralleling the connection will bypass the STT circuitry and severely deteriorate STT welding performance.

For additional Safety information regarding the electrode and work cable set-up, See the standard "SAFETY INFORMA- TION" located in the front of the Instruction Manuals.

CAUTION

Excessive voltage drops caused by poor work piece con- nections often result in unsatisfactory welding perform- ance.

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NEGATIVE ELECTRODE POLARITY

When negative electrode polarity is required, such as in some Innershield applications, reverse the output connections at the power source (electrode cable to the negative (-) stud, and work cable to the positive (+) stud).

When operating with electrode polarity negative the "Electrode Sense Polarity" DIP switch must be set to the "Negative" position on the Wire Drive Feed Head PC Board. The default setting of the switch is positive electrode polarity. Consult the Power Feed instruction manual for further details.

VOLTAGE SENSING

The best arc performance occurs when the Power Waves have accurate data about the arc conditions. Depending upon the process, inductance within the electrode and work lead cables can influence the voltage apparent at the studs of the welder. Voltage sense leads improve the accuracy of the arc conditions and can have a dramatic effect on performance. Sense Lead Kits (K940-10, -25 or -50) are available for this purpose.

CAUTION

If the voltage sensing is enabled but the sense leads are missing, improperly connected, or if the electrode polar- ity switch is improperly configured, extremely high weld- ing outputs may occur.

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The ELECTRODE sense lead (67) is built into the control cable, and is automatically enabled for all semi-automatic processes. The WORK sense lead (21) connects to the Power Wave 455M/STT (CE) at the four pin connector locat- ed underneath the output stud cover. By default the WORK voltage is monitored at the output stud in the Power Wave 455M/STT (CE). For more information on the WORK sense lead (21), see "Work Voltage Sensing” in the following para- graph.

All constant current processes sense the voltage at the out- put studs of the POWER WAVE 455M/STT (CE) by default.

POWER WAVE 455M/STT (CE)