If one of the windings, the primary, is connected to an alternating voltage source, an alternating flux will be produced in the magnetic circuit whose amplitude depends on the primary voltage.

• 如果给其中一个绕组（称为原绕组）施加交流电压，则它将在磁路中产生交变的磁通，磁通的大小取决于所加电压的大小。