If a watt-hour meter has a disk constant of 3.6, what is the primary Kh when used with 600:5 ampere current transformers and 20:1 potential transformers?

To determine the primary Kh (kilowatt-hour per revolution) of a watt-hour meter when used with specific current and potential transformers, it's essential to understand the relationship between the meter's disk constant and the transformations provided by the current and potential transformers.

The disk constant of the meter is 3.6 whr per revolution, meaning for each revolution of the disk, the meter records 3.6 watt-hours.

When employing current transformers, the primary current transformation ratio needs to be considered. In this case, the current transformer has a ratio of 600:5, which signifies that for every 600 amps on the primary side, the current transformer sends 5 amps to the meter. Therefore, the factor for the current transformer is:

600 / 5 = 120.

For the potential transformer with a transformation ratio of 20:1, it indicates that for every 20 volts on the primary side, the transformer sends 1 volt to the meter. Thus, the potential transformer factor is:

20 / 1 = 20.

To find the primary Kh, these factors are multiplied by the disk constant:

Kh = Disk Constant × Current Transformer Factor × Potential Transformer Factor.

Substituting the values we have:

Kh = 3