Service for finding the right current sense transformers

Würth Elektronik has expanded its free design tool REDEXPERT to include the Current Sense Transformer Selector. It allows developers to select the appropriate current sense transformers based on parameters relevant to their application.

Current sense transformers for measuring alternating current provide unique advantages over other current-sensing solutions: galvanic isolation, low power loss, high immunity to signal noise, and simple circuit design. Selecting the right current sensor can be a challenge, depending on the application. This Current Sense Transformer Selector offers a unique design tool previously not available on the market in this form.

After entering the parameters – current, frequency, signal type, and desired maximum error rate – the Selector finds all available options in the company’s product database that match these criteria. The tool provides a list of components with the corresponding parameters and simulates the temperature rise and the error as a function of frequency and current. The tool also enables the direct comparison of different options in a simulation view and provides an overview page with all relevant information for the selected component. These simulations, based on actual measurements, save developers from having to conduct their own tests when selecting current sense transformers (CSTs).

The selection process without the REDEXPERT Current Sense Transformer Selector is as follows: First, the CST must be selected with a suitable ET constant to ensure it doesn’t reach saturation even under unfavourable conditions, i.e. low frequencies and high currents. It is also important to ensure that the CST doesn’t overheat at maximum current. Last but not least, the error characteristics required for the specific application must also be taken into account when selecting the component. As datasheets for CSTs don’t cover all possible application-relevant parameters, and can’t realistically do so in practice, it is often necessary to test several components to make the best choice.

Typical applications of current sense transformers include AC current measurement, switched-mode power supplies, overload detection, load shedding/shutdown detection, metering, load measurement, and high-frequency current sensing.