SOLUTION

A universal motor is a motor that can work with either AC or DC, although it is almost always used with AC. It is sometimes called an AC commutator motor since it has a commutator and brushes like a DC motor. It is a commuted series-wound motor where the stator’s field coils are connected in series with the rotor windings through a commutator. Therefore they produce high starting torque. The universal motor is useful because it can work from the AC mains supply, but has some characteristics of a DC motor. These characteristics are

• High starting torque, which means the motor can reach full speed very quickly.
• The high running speed of between 10 000 and 30000 rpm (revolutions per minute).
• It can provide a wide variety of speeds when used with speed controllers.
• The universal motor works on the same principle that the DC series motor works. DC series motor has the characteristics of operating at high speed when there is no load and operating at low speed when the load is applied. It has high starting torque characteristics.
• So universal motor is used in mixers, where initially we put some load at starting.