please answer with construction idea.
A universal motor is similar to a DC motor with the armature connected in series with the field. If DC is supplied it works like any DC series motor. If AC is supplied, the stator and rotor field strengths will vary exactly in phase with each other. When the AC current changes direction, the stator and rotor fields will reverse at the exact same instant. Therefore, the torque will always be in the same direction even though the fields change direction because the stator and rotor fields always have the same relationship with each other. When connected to AC, torque magnitude pulses at twice the line frequency. Comparing operation at a given AC RMS voltage and an equal DC voltage, the torque at any given speed is lower for AC operation. That is due the higher impedance with AC and magnetic saturation at the peaks of the AC waveform. To avoid overheating due to eddy-current losses, series motors intended for use as universal motors are constructed with laminated stator and rotor cores.
