- on Test & Measurement
- Published in issue 4/2014 on page 38
Current Transformer Calculations
Understanding in-circuit current measurement
To calculate current we normally use a shunt to turn it into a voltage and measure the latter instead. But if we wish to measure the current in isolation, then a current transformer is the thing to use. How you actually do this is what we shall now describe. This method has the disadvantage that direct currents (DC) cannot be measured. Nevertheless there are numerous applications, for example in switch-mode power supplies, where the curve shape is the item of interest and we can dispense with the DC component.