I have a 220v motor stripped from a hair dryer that looks like a DC. How can I differentiate (visually or through tests) a DC motor from a AC / DC (universal) motor?
DC MOTORS ARE NOT 220V. It uses your wall without a large converter box that gets warm, so there isn't DC conversion. DC motors are usually 24 volts and under.
It could be a universal motor or a DC motor. I have seen some 240V hair driers with a permanent magnet DC motor and a single half wave rectifier diode. Some tests: If there is a rectifier diode in series with the motor it is almost certainly DC only (keeping in mind it could only be used to reduce the average voltage by 50%). If it has permanent magnets for the field it is DC only. There would be a rectifier somewhere. If it has a laminated core for the field winding that is universal meaning AC/DC. It has to be able to reverse the field and the armature at the AC rate. Generally the armature (rotating part) will look similar for all types.
The hair dryer motor is universal, ie it will run on AC or DC. The main difference between the two is that the AC motor has laminated field poles and is always a series connected motor. the only disadvantage of running a universal motor on AC is that you will get some sparking at the brushes.
