1. The current of the single-phase transformer at no load is different from the main flux, and there is a phase angle difference aFe because of the iron current. In addition, the no-load current is a cusp waveform because there is a larger third harmonic.
2. The AC flows in the armature winding of the DC motor. However, the current flowing in the field winding is a direct current. The excitation mode of the DC motor includes other excitation, shunt excitation, series excitation, and compound excitation.
3. The back EMF expression of the DC motor is E = CE F n, and the electromagnetic torque expression is Tem = CTFI.
4. The number of parallel branches of a DC motor is always paired. The number of parallel branches of the AC winding is not necessarily the same.