The peak voltage is the highest point or voltage value in any voltage waveform. A power quality issue arises when Pulse Width Modulation (PWM) devices, such as variable frequency drives, are added to a power system with a peak voltage equal to the square root of two times the RMS voltage. The peak voltage, for instance, if the RMS voltage is 85 V. The average voltage and maximum voltage of AC power coming from the wall are both about 110 V. Therefore, the real peak voltage is 120/0.707 = 170 V. The sinusoid's amplitude is divided in half by this. Peak-to-peak voltage (Vp-p), also known as the total amplitude, is 340 V, or twice the peak voltage.
