What is a Form Factor?

Definition

The Form Factor is defined as the ratio of the root mean square (R.M.S) value to the average value of an alternating quantity (either current or voltage). The average value of an alternating quantity is the arithmetic mean of all instantaneous values of current or voltage over one complete cycle.

Mathematically, it is expressed as:

Ir.m.s and Er.m.s are the root-mean-square values of current and voltage respectively, while Iav and Eav are the average values of alternating current and voltage respectively.

For a sinusoidally varying current, the Form Factor is given by:

The value of the Form Factor is 1.11.

There is an inherent relationship among the peak value, average value, and root mean square (R.M.S.) value of an alternating quantity. To characterize the relationship between these three quantities, two important parameters are introduced in engineering: Peak Factor and Form Factor.

The Form Factors for various waveforms are as follows:

• Sine wave: π/(2√2) ≈ 1.1107

• Half-wave rectified sine wave: π/2 ≈ 1.5708

• Full-wave rectified sine wave: π/(2√2) ≈ 1.1107

• Square wave: 1

• Triangle wave: 2/√3 ≈ 1.1547

• Sawtooth wave: 2/√3 ≈ 1.1547

This concludes the basic concept of the Form Factor.