A universal motor is one that can be operated on either direct current or single-phase alternating current at approximately the same speed. This motor is most popular in the fractional-horsepower size and is used on household appliances such as vacuum cleaners, food mixers, drills, sewing machines and power handsaws.
- The most popular type is similar to the small two-pole series motor with two concentrated field poles.
- Another type of universal motor has a field winding distributed in slots, much the same as the split-phase motor.
These motors are generally made in sizes varying from 1/200 to 1/3 hp, but are obtainable in much larger sizes for special applications.
Construction of Universal Motors
- field core
- end plates.
The armature is similar to that of the small DC motor. It consists essentially of a laminated core having either straight slots or skewed slots and a commutator to which the leads of the armature winding are connected. Both the core and commutator are pressed on the shaft.
As in other motors, the end plates are located on the ends of the frame and held in place by screws. The plates house the bearings, usually of the ball or sleeve type, in which the armature shaft revolves. Many universal motors contain an end plate that is cast as part of the frame. Only one plate can be removed from this type of motor.
Brush holders are usually bolted to the front end plate.