**Heat Input Formula**

Under arc welding process, heat input and arc energy are the measures of energy that has been supplied to the piece to form a weld. Both are measured in units of energy per unit length.

It refers to a characteristic or dimension such as weld length, a bead, the diameter of a weld spot or cross section. The amount of heat input which goes into a weld is determined as a function of time.

The heat input formula is given by,

Heat input = Voltage(V) × current(A) x time / distance travelled×1000

The accurate measurement of arc voltage is the difficulty here, but we mostly measure load voltage at the output terminals of the current source.

**Example1**

Determine the heat input of the engine which operates in 2000 V with a current of 5500 calories. The distance is 10 ft with time 40 sec.

**Solution:**

Given data parameters are

Voltage = 2000 V

Current (A) = 5500

Distance travelled = 10 ft

Time = 40 sec

Substitute all the values in the given formula.

Heat input = Voltage × current × time / distance travelled × 1000

= 2000×5500×40 / 10 ×1000

Therefore, Heat input = 44000 Joules / ft.

**Example 2**

A heat engine operates at a voltage of 1500 V with a current of 3400 A. Determine the heat input if the distance is 24 ft with time 80 sec.

**Solution:**

Given parameters are

Voltage = 1500 V

Current (A) = 3400 A

Distance = 24 ft

Time = 80 sec

Substitute all the values in the given formula.

Heat input = Voltage × current ×time / distance travelled×1000

= 1500 × 3400 × 80 / 24 x 1000

Therefore, Heat input = 17000 joules / ft.