SOLUTION

If a particular application needs high-speed and high starting torque, then a universal motor will be preferred.

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.
• 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.

Universal motors are used in many small appliances and hand-held tools such as food mixers, blenders, vacuum cleaners, drills, grinders, saws, and weed trimmers.