CABLE CONNECTORS AND RETURN CLAMPS

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CABLE CONNECTORS AND RETURN CLAMPS
A connector is fitted to a cable in order to
connect the cable to the power supply unit, to
connect two cables together, or to connect the
cable to the work
Lug Used to make a permanent connection such as
to the welding bench
Screw type return clamp used when return is moved
occasionally.
Spring return clamp useful when the return is
moved frequently
Any high resistance in the return circuit may
cause overheating The contact area should be
cleaned before attaching the connection.
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The three most important connections in the
external welding circuit are
A The welding lead B The welding return C The
welding earth
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Electrode Holders
Tong type electrode holders
This type of holder gives much quicker electrode
changing than the screw type but does not grip
the electrode as securely. The partially
insulated type is only suitable for bench-work

• Maintenance checks
• Check insulation for damage at jaws
• Check jaws for wear and grip all sizes
• Check spring has not lost tension due to
  overheating
• Check cable is secure

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Screw Type Holders
Screw type holders are fully insulated and should
provide a firm grip on a wide range of diameters

• Maintenance checks
• Check insulation for damage and cracks
• Check for grip grip all sizes of electrode
• Check screw thread for wear
• Check cable is secure
• N.B. Do not apply oil or grease to screw thread
  as this will pick up abrasive grit and cause wear.

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Manual Metal Arc Welding Equipment Inspection and
Maintenance
Cables and connections
The general maintenance of cables covers two main
areas, cables which are used to connect the mains
supply to the welding power source unit and
cables which are used on the output side, i.e.
welding lead, welding return and welding earth.
Mains cables A welder needs to check the mains
lead regularly, but this must be done when it is
NOT connected to the mains supply. If a fault is
found, it must be reported to a responsible
person who should designate an electrician to
carry out repairs.
Typical faults are - defective insulation, cut
or burned or cracked, loose connections at plug,
isolator or power source. May be caused by moving
the power source when still connected. Hazard
Electric shock, fire risk. Action Do not switch
on if insulation is damaged, report to
responsible person.
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Welding Cables These are made from stranded
copper or aluminium and covered in an insulating
material usually a rubber compound. Copper and
aluminium are used because they are good
conductors of electricity. The welding lead and
welding return may trail on the floor and are
likely to become damaged. Typical Faults Damaged
Insulation Cuts, burns, cracks. Hazards
Electric shock, stray arcing, burns Action
repair by vulcanising insulating tape is used for
temporary repairs only.
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Damaged or cut conductors Damaged conductors may
not be able to carry the full welding
current. Hazards Overheating cables, fire,
electric shock, current may find alternative path
e.g. through other equipment. Action damage at
either end of a cable can be repaired by making a
new connection. Damage in the middle of a cable
can be repaired by cutting in two and fitting an
insulated plug and socket.
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The Welding Earth
In addition to the welding return, the work
should be earthed with a cable of sufficient
cross section to carry the welding
current. Reasons for earthing the work If the
return lead makes a bad connection or falls off.
The electrode may make the work live. Welding
current mayfind another path through the earth
wire in portable equipment such as drills or
grinders resulting in a fire.
Persons coming into contact with the work which
is live may be electrocuted.
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MANUAL METAL ARC WELDING POWER SOURCES

• THESE MAY BE CLASSIFIED INTO TWO GROUPS
• ALTERNATING CURRENT A.C.
• DIRECT CURRENT D.C.

SINGLE OPERATOR MAINS TRANSFORMER SETS.
THESE MAY BE OIL COOLED OR AIR COOLED. THE OPEN
CIRCIUIT VOLTAGE IS NORMALLY 50 OR 80 VOLTS
Maximum permitted O.C.V. 80V THE ELETRICAL
INPUT TO POWER SOURCES IS CALLED SINGLE PHASE.
IF THE MACHINE USES 415 TO 440 VOLTS IT WLL BE
CONNECTED TO A PAIR OF LINES ON THE 3 PHASE
SYSTEM.
Air cooled Annually remove panels and blow out
with dry compressed air Oil cooled Annually
Check oil level and top up as necessary.
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BALANCING THE LOAD
When a number of single operator welding machines
are in use, it is usual to connect them so that
the load on the three phase system is balanced as
far as is possible. In practice the supply will
never be in perfect balance. The best way to
achieve this balanced load is to use a multi
-operator transformer.
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MULTI - OPERATOR 3 PHASE TRANSFORMER SETS.
Multi -operator sets are available to supply 3,
6, 9 or 12 current regulators (chokes) ADVANTAGE
OVER SINGLE OPERATOR This type of system always
draws a balanced load from the three phase supply
even if only one welder is working. Open circuit
voltage is 80 volts maximum
Advantages of A.C. Mains Power Sources over D.C.
Generators

• Lower cost of equipment
• Less maintenance
• Higher efficiency
• Very little power consumed when idling
• Arc blow does not occur when using A.C.

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D.C. POWER SOURCES
D.C. GENERATORS
ELECTRIC MOTOR DRIVEN GENERATOR
DEISEL ENGINE DRIVEN
The engine driven type is generally used for site
work.
The d.c. generator is a rotating machine which
can be driven by an electric motor, petrol or
diesel engine.
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TRANSFORMER RECTIFIER SET

• This type of power source is operated from the
  mains supply.
• The transformer steps down the mains voltage to a
  suitable welding voltage,
• The rectifier changes the alternating current
  into direct current.
• Very often this type of machine can be switched
  to give either alternating or direct current as
  required.
• This type of machine is more efficient than a
  generator, running costs and maintenance is much
  less.

ADVANTGES OF D.C. OVER A.C.

• . Smoother flow of current.
• . Engine driven type are portable.
• . Choice of polarity 2/3 heat positive 1/3 heat
  negative.
• . Easier welding of thin sheet (electrode
  positive)
• . Better control of penetration.
• . Aluminium electrodes can be used.

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Moving Core Transformer

• A SINGLE OPERATOR A.C. TRANSFORMER WITH A MOVING
  CORE.
• Advantages
• Step-less current adjustment
• Current can be adjusted during welding.

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D.C.Inverter Set

• ADVANTAGES
• Portable weighing only six kilograms
• Very smooth output
• Designed for Manual Metal Arc or Tungsten Inert
  Gas.
• Does not cause surge on power supply when
  striking arc (compared to transformer set)

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• ADVANTAGES OF A.C. MAINS POWER SOURCES OVER D.C.
  GENERATORS
• . Lower initial cost of equipment
• . Less maintenance.
• . Higher efficiency
• . Very little power consumed when idling.
• . Arc blow does not occur when using a.c.

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Welding Cables These may be made from stranded
copper or aluminium and covered in an insulating
material usually made from a rubber
compound. Copper and aluminium are good
conductors of electricity The welding lead and
welding return may trail on the floor an are
likely to become damaged.
Typical faults Damaged insulation, cuts burns
cracks etc, damaged insulation should be repaired
by vulcanising, insulating tape is only to be
used for temporary repairs. Hazards Electric
shock or stray arcing Damaged or cut
conductors if the conductors are broken the
cable may not be able to carry the full welding
current. Hazards Overheating cables, current
finding alternative paths through other
electrical equipment, electric shock