Welders & Filters

Question 1

What are the most important ratings when replacing resistors

Answer 1

Power
Resistance
Tolerance
The maximum voltage

Question 2

What does the fourth band of a resistor represent?

Answer 2

Tolerance

Question 3

Three characteristics that affect the capacitance of the capacitor:

Answer 3

Surface area of the plates
Distance between the plates
Dielectric constant between the plates

Question 4

Electrolytic capacitors are polarity sensitive. T or F?

Answer 4

True

Question 5

A capacitor can be used as what sort of device to block dc and pass ac if placed in series?

Answer 5

Coupling device

Question 6

Inductors are sometimes used in electrical circuits where a sudden rise or fall of current is undesirable. T or F?

Answer 6

True, the application must be able to withstand the spikes (noise or dirty power)

Question 7

What are the two most important ratings of a coil?

Answer 7

Inductance
Current

Question 8

What is the ripple formula?

Answer 8

Vrms of the ripple / Vdc average x 100

Question 9

When dealing with the L-Section filter, the capacitor provides good filtering with large loads While the choke is more effective with small loads. T or F?

Answer 9

False. Capacitors are good with small loads, and chokes are good with large loads.

Question 10

What does a filter do?

Answer 10

Used on the output of rectifiers to produce smooth dc.

Question 11

What does ‘MIG’ stand for in respect to welding?

Answer 11

Metal Inert Gas

Question 12

Describe the basic GMAW process.

Answer 12

Involves feeding a wire electrode through a tube onto the surface to be welded.

Question 13

The three main components of a GMAW welder are:

Answer 13

Step-down transformer
The rectifier
The filter

Question 14

GMAW welders weld with:

Answer 14

DC source

Question 15

What is the simplest filter?

Answer 15

A capacitor filter is the simplest

Question 16

You can change heat settings on a welder by using which taps on a Transformer

Answer 16

Primary or Secondary

Question 17

Name the values of these resistors:

R1: R22
R2: 22K
R3: 2M2

Answer 17

R1: 0.22 ohms
R2: 22k ohms
R3: 2.2M ohms

Question 18

Mica capacitors are temperature stable. T or F?

Answer 18

True. Mica is also a good insulator.

Question 19

When a capacitor is connected to a dc supply, what occurs?

Answer 19

The cap acts as a short circuit as the opposite charges are attracted to each other on the plates of the capacitor. Resulting in maximum current flow in the circuit.

Question 20

When testing a charged capacitor, treat it as a ______ _______.

Answer 20

Charged battery

Question 21

Describe Lenz Law

Answer 21

The direction of the induced emf is such that any current resulting from it develops a flux that opposes any change in the original flux.

Question 22

What is the formula for time constants dealing with Inductors?

Answer 22

T = L / R

Question 23

If you get an OL reading with an inductor coil, what is the problem?

Answer 23

Its become open-circuited- several windings may be shorted together because the insulation has broken down.

Question 24

A variation in the magnitude of voltage is called

_______ , and is sometimes reffered to as the the ac component of ________.

Answer 24

1. Ripple
2. Voltage

Question 25

A power supply with a low percent ripple has a more constant (or cleaner) dc voltage than one with a high percent ripple. T or F?

Answer 25

True.

Question 26

To prevent the metal from oxidizing or burning when its molten during welding, what is applied to the arc area?

Answer 26

An inert shielding gas is supplied to displace air containing oxygen

Question 27

What does the welding machine control?

Answer 27

The amount of current The rate of electrode feed The amount of shielding gas

Question 28

What is the definition of Welding?

Answer 28

The process of joining metal components by heating them until they become liquid, letting the metal pieces fuse together and then allowing them to cool to form a strong joint.

Question 29

Seam welding machines, spot welding machines and box welding machines are resistance welders. T or F?

Answer 29

True

Question 30

How is a choke filter connected?

Answer 30

An inductor coil connected in SERIES with the output of a rectifier and in series with the load.

Question 31

How is a capacitor filter connected?

Answer 31

The capacitor is connected in parallel with the output terminals of a rectifier and in parallel with the load.

Question 32

How is an L-Section Filter connected?

Answer 32

With the capacitor connected across the output after the choke. Reducing the possibilty of voltage spikes at the load produced by the choke. Also called a choke-input filter because the choke inputs to the capacitor.