1. Low frequency transformer is used to transmit signal voltage and signal power, but also can realize the impedance matching between the circuit, has isolation effect on DC. High frequency transformer and low frequency   transformer principle no difference. But because the frequency of high frequency and low frequency is different, the iron core used in the transformer is different. Low frequency transformers generally use high permeability silicon steel sheet, high frequency transformers with high frequency ferrite core.

2. In general, the low-frequency transformer refers to the "power frequency transformer". It is used to change the voltage at the power frequency (50Hz). That's the kind of transformer you're talking about with silicon steel sheets.

3. About the high frequency transformer, refers to the transformer working in high frequency, plays the role of energy conversion. Because the frequency of the magnetic field is very high, eddy current will be generated in the silicon steel sheet (the conversion speed of the small magnet in the silicon steel sheet can not keep up with), so the high-frequency transform generally uses "high-frequency ferrite" for the magnetic core.

4. Be cause the high frequency current through the high frequency transformer, most of it is "non-sine wave", therefore, it is customary to call "transducer" more accurate.