# Construction of Universal Motors

- Link: https://studyelectrical.com/2014/12/construction-of-universal-motors.html
- Published: 2014-12-03T07:41:00+00:00

A universal motor is one of the [single-phase motors](https://studyelectrical.com/2014/05/single-phase-induction-motor.html)
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 in household
appliances such as vacuum cleaners, food mixers, drills, sewing machines, and power
handsaws. 

![universal motor construction](https://studyelectrical.com/wp-content/uploads/2014/
12/universal-motor-construction.jpg)

Universal Motor

Universal motors are series-wound and have a high starting torque and a variable
speed characteristic. They run at dangerously high speed without a load, and because
of this, they are usually built into the device they drive. 

 

[⌊Untitled 3⌉⌊Untitled 3⌉[

Series Connection of Armature and Field in Universal Motor

There are several types of universal motors in use today. 

 * 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

Different parts of Universal Motors are discussed here. The main parts of the concentrated
field universal motor are,

 1. **frame**
 2. **field core**
 3. **armature**
 4. **endplates.**

[⌊Parts of a Universal Motor⌉⌊Parts of a Universal Motor⌉[

Parts of a Universal Motor

The frame is a rolled steel, aluminum, or cast-iron shell similar to that in Figure
2 and large enough to hold the field core laminations comfortably.

The field poles are generally held in the frame by means of thru-bolts.

Very often the frame is constructed to form an integral part of the machine it supports.

[⌊Untitled 1⌉⌊Untitled 1⌉[

Frame of Universal Motor

The field core is constructed of laminations that are tightly pressed together and
held by rivets or bolts. As shown in Figure, the laminations are designed to contain
both field poles of a two-pole motor.

[⌊Untitled 1⌉⌊Untitled 1⌉[

Field Core

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.

[⌊Armature of Universal Motor⌉⌊Armature of Universal Motor⌉[

An armature of Universal Motor

As in other motors, the endplates are located on the ends of the frame and held 
in place by screws.

[⌊Untitled 3⌉⌊Untitled 3⌉[

End Plates of Universal motor

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 endplate.

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