The issue of multiplier factors for electricity meter readings
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This post was last edited by zyz8438 on 2010-10-14 at 10:35. Here, the reading on the meter in the three-phase electrical cabinet needs to be multiplied by 60 to get the actual amount of power used. Could someone explain why it’s necessary to multiply by 60?
The turns ratio of the current transformer is 300/5A, which means that the actual current consumed is 60 times the measured current flowing through the meter. So the meter reading should be multiplied by 60.
This post was last edited by zyz8438 on 2010-10-14 08:52. Meters (including wattmeters, active power meters, reactive power meters, etc.) are connected directly to the primary circuit only in low-voltage circuits with low current levels (usually below 100A). In most cases, it is connected to the secondary circuits of current transformers and voltage transformers. Since both current transformers and low-voltage transformers involve transformation of ratios (K1 and K2), attention must also be paid to the multiplier factor (K3) when selecting electricity meters. The meter reading must be multiplied by 60 to obtain the actual amount used; obviously, this is because the multiplier setting on the electricity meter was not chosen correctly, resulting in K1*K2=60K3.
Low-voltage electricity meters generally do not use voltage transformers; therefore, there is no voltage transformation ratio. I do not understand what the moderator meant by saying \"Obviously, it is because the transformation ratio of the electricity meter was not chosen correctly, resulting in K1*K2=60K3\"“
In low-voltage circuits with low current, current transformers and voltage transformers are not required; we can assume that K1=1 and K2=1. For low-voltage, high-current circuits, a voltage transformer is not required, but a current transformer is needed; it can be assumed that K2=1, while K1 is a constant different from 1. For high-voltage circuits that require both current transformers and voltage transformers, K1 and K2 are constants that are not equal to 1. Since the original poster didn’t specify whether it was high voltage or low voltage, I talked about both together!
There is an issue related to the multiplication factor. For circuits that provide voltage directly (usually 380V or 660V), the value can be calculated by multiplying the electricity consumption figure by the multiplication factor of the current transformer. Based on the figures you mentioned, if the multiplication factor is 60, then the transformer used is of the 300/5 type. In cases where the voltage is 6KV or 10KV or higher, it’s not possible to connect the voltage directly to the meter; instead, a voltage transformer is used for voltage transformation, with the usual secondary voltage being 100V. In such cases, the electricity consumption value is calculated by multiplying KW·H by the current transformation ratio and the voltage transformation ratio. The voltage transformation ratio is easy to calculate as well: 6000/100 gives a multiplication factor of 60, while 10000/100 gives a multiplication factor of 100. Thus, the result is straightforward.