WE-CST High Frequency Transformers Würth Elektronik WE-CST High Frequency Transformers offer a frequency up to 1MHz, 80V rated voltage, and 500VAC to 750VAC insulation test voltage. These transformers are created with an innovative manufacturing process making the transformers extremely small with better insulation. WE-CST Type EE4.4 transformers are offered in nine different winding ratios from 1:20 to 1:150. With an insulation voltage of 750VAC, type EE4.4 transformers are suitable for a broad range of high-frequency applications up to 1MHz with currents up to 7A. These tiny current sense transformers are ideally suited for high frequency current sensing applications where small component size and outstanding isolation are vital.