How to measure AC voltage?

Answer: The measurement of AC voltage is divided into single-phase AC voltage measurement and three-phase AC voltage measurement.
(1) Single-phase AC voltage measurement:
Single-phase AC voltage measurement usually uses an AC voltmeter. When connected to the measured circuit, attention should also be paid to the selection of the range, but there is no requirement for polarity.
When measuring, the voltmeter can be directly connected; in order to expand the range, a voltage transformer is often used, but the transformer should not be short-circuited for secondary measurement to ensure safety.
The direct connection method of the voltmeter is shown in Figure 3-7.
The direct connection method with a voltage transformer is shown in Figure 3-8.

3-7, 3-8

〔2) Measurement of three-phase AC voltage:
Three-phase AC voltage can be measured with three voltmeters. The three meters read the measurement data at the same time, and the measurement accuracy is relatively high. However, for the sake of saving, one voltmeter is usually used to make three measurements to obtain the three-phase voltage data. A voltage conversion switch is also commonly used to measure the lower phase voltage data with one voltmeter. At this time, the voltmeter can be fixedly wired, which is more convenient to operate. Various connections for three-phase AC voltage measurement are shown in Figures 3-9.

3--9