PEAK VALUE

The maximum value attained by an alternating quantity during one cycle is called ‘peak value’. This is also called ‘maximum value or crest value or amplitude’. A sinusoidal alternating quantity obtains its maximum value at 90° as shown in Figure 6.7. The peak of an alternating voltage and current is represented by E_m and I_m. The knowledge of peak value is important in case of testing dielectric strength of insulating materials.

6.12  AVERAGE VALUE

The arithmetic average of all the instantaneous values considered an alternating quantity (current or voltage) over one cycle is called average value.

In case of symmetrical waves (such as sinusoidal current or voltage wave), the positive half is exactly equal to the negative half; therefore, the average value over a complete cycle is zero. Since work is being done by the current in both the positive and the negative half cycle, average value is determined regardless of signs. Hence, to determine average value of alternating quantities having symmetrical waves, only (positive half) cycle is considered.

Divide the positive half cycle into ‘n’ number of equal parts as shown in Figure 6.8. Let i₁, i₂, i₃, …, i_n be the mid-ordinates.

Average value of current, I_av = mean of mid-ordinates.

Fig. 6.8  Positive half cycle divided into n equal parts