Effects of a Volt-ampere Curve On a Welding Arc Flashcards Preview

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Flashcards in Effects of a Volt-ampere Curve On a Welding Arc Deck (21)
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1

What happens to the volts and amps when you have a short arc vs a long arc?

Short arc= low arc voltages and high welding currents
Long arc= high arc voltage and low welding currents

2

What are 2 classifications for welding power sources and which one is better for SMAW?

Constant current (CC) and constant voltage (CV). Constant current is standard for SMAW

3

What is an open circuit called? (OCV) what is the OCV range?

Open circuit voltage (OCV) 50 to 100 v normally around 70V

4

What is the middle of the volt-amp curve called? And what is its normal range?

The normal voltage levels during welding also known as the "arc voltage". Its normal range is 18v to 36v

5

Explain the difference between CC and CV

CC has a "drooping" (or sloping") electrical characteristic. This drop indicates that the current of the arc will remain fairly stable across a wide range of voltage changes


Constant voltage power sources have a fairly flat volt-amp curve. Power sources of this type produce a very stable voltage regardless of the amount of current.

6

What happens to the volt-amp curve when you have a higher open circuit voltage (OCV) vs a lower (OCV)?

Low range is better for?
High range is better for?

Higher OCV slope is steeper and Lower OCV slope is flatter.

With a flat volt-amp curve, and change in arc length will be noticeably change the current level. With a steep volt-amp curve, any change in arc length will only cause minor current change


Low range is better for out of position welding
High range is better for flat and high-production welding

7

What control on a welding power source gives you some controls over the volt-amp curve?

Arc dig, crisp and soft or arc force control

8

Ac transformers used as welding power sources are also called _________. Line voltages for single phase and 3 phase are? The transformer converts these line voltages into open circuit welding voltages in the range of?

Step-down transformers
115v or 220v for single phase and 115v, 208v, 480v or 575v for 3 phase

Open circuit line voltages in the range of 60v to 80v with amps as high as 1500A

9

Explain a transformer/rectifier

The transformer part transforms the AC line current down into usable AC current and the rectifier converts it to DC. This can be used with either single phase (with a capacitor to get consistent currents) or 3 phase

10

Explain AC/DC transformer/rectifier

Works just like a transformer/rectifier but have a switch to bypass the rectifier circuit to produce AC currents

11

What part of an engine driven power source reduces and increases the engine speed when you're welding?

The governor

12

What are the dials on an engine driven welding power source that let's you control the volt-amp curve?

"Dual control welding power sources" also known as "job select dials"

Tapped type, the stepped type or continuous control type. The tapped and stepped type offer a range of prescribed settings. The continuous control type allows for infinite settings adjustment

13

Describe the steps an inverter takes

What is the efficiency of a transformer vs an inverter

•Takes in ACine power
•rectify it to DC
•Converts it to electronically to high-frequency (3 to 50 kilohertz) AC
•Transforms it to welding voltages
•Converts it back to AC

Conventional transformer at 60 Hertz would weigh 19.5 kg (42 Ib). It would have an efficiency of 90% and produce a heat loss of 10%

An equivalent inverter operating at 200 000 hertz would weigh 1.5kg (3 1/3 Ib). It would operate at 98% efficiency and produce only 2% heat loss

14

A standard transformer/rectifier can lose how much of its incoming power vs the energy loss of an inverter

55% and as low as 15%

15

What does NEMA and ASME stand for?

National Electrical Manufacturers Association
American society of mechanical engineers

16

Explain duty cycles and their grading system

Duty cycle is the length of time a welding power source can be used continuously at its rated capacity during any 10min period.

Grade 1 is 100%, grade 2 is machine and light industrial and grade 3 is light duty usually below 20%

17

What is the electrode holder called? And two most common types

Stinger
Jaw and twist type

18

4 types of ground clamps

Spring-loaded clamp , C-clamp, Rotary clamp and Magnetic clamp

19

The 4 layers around the copper wire in the welding cable.

A durable paper to allow the conductor to move easily inside the insulation when bent. A layer of rubber insulation surrounded by a layer of woven fabric reinforcement to provide additional wear resistance. The outer layer us a special composition rubber with a smooth finish, highly resistant to wear.

20

Name the different sizes of cables and the most commonly used

4 to 4/0

2 to 2/0 used 15m/50ft. 100A with 2 to 500A with 2/0

See chart on page 83 for longer length of cable

21

The connection to the electrode holder is usually a _________ while the connection to the ground clamp can be ________ or _________. What is used to increase cable (lead) length? What are the 2 main types of connectors that are used between welding cables and the welding power source?

Mechanical one, a mechanical one or uninsulated lug bolted to the clamp.

Twist lock quick connectors are the most convenient a "whip" (short length of cable) is also sometimes connected to the holder to increase flexibility and reduce fatigue.


Built in quick connectors or uninsulated lugs