Where Does It Say Saturation on the Datasheet?
Unfortunately, most transformer datasheets are not much help in providing specifications for low frequency performance. Some provide a vague ‘Frequency Response’ range. Our tests indicate that this is usually hopelessly optimistic if not dishonest: the power bandwidth at the low end is generally much lower than the specification. Fortunately, since no secondary load is required to observe saturation, bench measurements are easy. Connect a sinewave source to the primary with a small-value resistor in series. Measure the rms voltage across the primary with a voltmeter or an oscilloscope. Similarly measure the voltage across the resistor. Start at 1 kHz and sweep downwards. Across the resistor, you should measure a small voltage (proportional to primary current) that increases slowly as you decrease frequency. At some frequency, you will observe an abrupt increase in resistor voltage, indicative of the onset of saturation. Change the drive voltage and repeat the sweep. You should be able
