Power Supply

Question 1

What power supply is needed for electric arc welding

Answer 1

The power supply needed to create the arc for Arc Welding must be a high current A.C. or D.C. supply.

Question 2

Where is A.C supplied from and at what voltage is it?

Answer 2

Alternating current is supplied from the mains at 220V.

Question 3

Is current directly or inversely proportional to voltage?

Answer 3

Current is inversely proportional to voltage

Question 4

As current is inversely proportional to voltage, what must be done to the voltage to get an increased current suitable for welding?

Answer 4

A transformer is used to reduce the voltage from 220 volts AC to around 100 volts AC, thus giving an increased current suitable for welding.

Question 5

Why does a transformer have to reduce the voltage from 220 volts AC to 100 volts AC?

Answer 5

To get an increased current suitable for welding.

Question 6

If the process requires DC current, what needs to be used in conjunction with a transformer

Answer 6

If the process requires a DC current, a bridge rectifier is used in conjunction with a transformer.

Question 7

This transformer-rectifier circuit converts AC at high voltage to what?

Answer 7

This transformer-rectifier circuit converts AC at high voltage to DC at low voltage.

Question 8

This transformer-rectifier circuit converts what to DC at low voltage.

Answer 8

This transformer-rectifier circuit converts AC at high voltage to DC at low voltage.

Question 9

In the case of Tungsten Gas Shielded Welding, how many circuits are used?

Answer 9

In the case of Tungsten Gas Shielded Welding, two circuits are used, one high-frequency circuit to start the arc, and another circuit to maintain the arc while welding

Question 10

Name the two circuits used in the case of tungsten gas shielded welding

Answer 10

One high-frequency circuit to start the arc, and another circuit to maintain the arc while welding

Question 11

The transformer rectifier circuit does three key things to the 220 volts A.C. mains supply, list these three things:

Answer 11

1. Firstly the 220 volts A.C. is stepped down to around 100 volts in the step-down transformer, which creates a high current A.C. supply, as current is inversely proportional to voltage.
2. This A.C. supply is run through the bridge rectifier, as the diodes only allow current flow in one direction, this gives a D.C. output.
3. This D.C. output from the rectifier can be uneven, so a smoothing capacitor is used to ensure an even distribution of current flow to the electrode for welding.

Question 12

Safety precautions associated with Electric Arc Welding and equipment includes: (6)

Answer 12

1. Ensure that equipment is well maintained with cables secured and insulated properly to prevent electric shock.
2. Appropriate ventilation systems should be in place to minimise the inhalation of fumes while welding.
3. Protective clothing should be worn including leather gloves, apron, etc.
4. A good quality welding shield with darkened faceplates must be worn to protect the user.
5. Appropriate welding curtain or cubicle will ensure that others are not exposed to the UV light emitted from the welding process.
6. Ensure that work is appropriately secured.