The type of motor that operates on both DC and single phase AC supply is called Universal Motor. The universal motor is also called an ac series motor. The universal motor works at approximately the same speed and output on either DC or AC single-phase supply.
The universal motor is a series-wound motor which means field winding and armature windings are connected in series. It has high starting torque and variable speed characteristics. It runs at dangerously high speed when running at no load.
Universal motors are designed for commercial frequencies from 50Hz or 60Hz to DC zero frequency and for voltage rating 250V to 1.5V.
Universal motors are generally used in Electric hand drills, vacuum cleaners, electric shaver, sewing machines, and in many more applications.
This motor is a commutator type motor.
If an ac series motor is connected to an AC supply it will rotate and exert one-directional torque because the current flowing in both field and armature is the same and reverse at the same time.
The direction of torque developed in DC series motor is determined by both field polarity and the direction of current flowing through armature winding.
Construction Of Universal Motor
The construction of a universal motor is identical to the construction of a DC series motor. It is a series-wound motor that means field and armature windings are connected in series. the universal motor diagram is shown below
Types of Universal Motor
Generally constructed in two types
- Non compensated with concentrated pole type
- Compensated with distributed field type
Non compensated with concentrated pole types
The non-compensated type universal motor has 2 salient poles like DC series motor except the laminated core. The laminated stator is constructed to reduced eddy current losses because the flux is alternating when it is operated on AC supply.
The armature is wound type same as a small DC motor, it has a laminated core having straight or skewed slots and a commutator to which armature winding leads are connected.
Compensated with Distributed field type
It has a stator same as the split-phase motor and wound type armature similar to that small dc motor.
In compensated type motor, compensating winding is used to reduced reactance voltage drop in armature when it operated on AC supply. This voltage is caused by the transformer action due to alternating flux.
If compensated winding connected in series with armature and field winding in such a case motor is called a conductively compensated motor. the connection diagram is shown below.
Working Principle of Universal Motor
Universal motors working principle is the same as the DC series motor works.
Let,
DC series motor connected to single-phase ac supply and the same current flowing through the field and armature windings., hence the ac reversal from positive to negative cycle or from negative cycle to positive will simultaneously affect both field flux polarity and the current direction through armature winding.
This shows that the direction of torque developed will remain positive and rotor rotation will continue in the same direction. Thus, independent of supply fed. universal motors working principle is the same as the DC series motor works.
The nature of the torque developed will be pulsating and the frequency will be twice the supply frequency. thus universal motor(ac series motor) can run on both DC and single phase AC supply.
AC series motor specially designed to run on DC supply suffers the following drawbacks when it operates on a single phase AC source.
- Its efficiency is low due to hysteresis and eddy current losses.
- Its Power factor is low due to the large reactance of field and armature winding.
- Sparking at the brushes is more.
To overcome the above drawbacks of DC series motor to run efficiently on ac supply following constructional modifications are done.
Field core is constructed using a material that has low hysteresis losses and it laminated to reduced eddy current.
The field winding is constructed with small numbers of turns due to this pole area increase and flux density decreases this reduced iron losses and reactive voltage drop.
The number of armature conductors increases to achieve the required torque with low flux.
Compensation winding is used to reduce armature reaction and increase commutation.
Universal motors are electric motors that can be driven by either AC or DC electricity. in this article, we are going to see the Advantages and disadvantages of universal motors.
They are also known as series-wound motors and are used in a wide range of applications due to their unique design and versatility.
Advantages of Universal Motor
These motors have a number of advantages over other types of electric motors, such as being able to operate at higher speeds and with greater efficiency.
- They also have the ability to be operated on both AC and DC power, making them an ideal choice for many applications.
- Universal motors are also relatively low-cost and generally easier to maintain than other types of electric motors.
- They are typically found in household appliances, industrial equipment, and even some automobiles.
- They also have higher torque and better speed control than other types of motors.
- Additionally, they are smaller than traditional motors, making them ideal for applications where space is limited.
- Finally, universal motors are relatively inexpensive and easy to maintain.
- This makes them an attractive option for many users.
Disadvantages of Universal Motor
Despite their popularity, there are a few limitations associated with universal motors that should be considered when deciding if they are the right option for your application.
- As these motors are designed for use in a wide range of applications, they cannot always offer the best performance for specific tasks.
- Even though Universal Motors can handle a variety of voltages, their maximum output power is limited; this means that for particularly demanding applications, such as those requiring high torque or speed, an alternative may be necessary.
- Additionally, Universal Motors require more maintenance than other motor types and generate higher levels of noise when running at high speeds.
- Furthermore, they have a shorter lifespan than dedicated motors and need to be replaced more frequently.
Applications of Universal Motors
- Universal Motors have a broad range of applications and can be used in many different ways.
- They are commonly found in vacuum cleaners, power tools, blenders, food processors, electric drills, and lawnmowers.
- In addition, they are also used in medical equipment such as dental drills and laboratory mixers.
- used in industrial applications such as conveyor belts and material handling systems.
- In addition to their traditional uses, Universal Motors are being used in an ever-growing number of renewable energy applications.
- Solar-powered motors and wind turbines often rely on Universal Motors for their power.
- Furthermore, Universal Motors are also used in hybrid vehicles to provide additional power when needed.
- it is used in a variety of other applications, including robotics, aerospace engineering, and home automation.
- With their versatility and durability, Universal Motors are becoming increasingly popular in a wide range of industries.
This motor is a kind of motor which construction is done to work on both DC and Ac single-phase supply. The working principle is the same as the dc series motor and has an advantage as the dc series motor like high torque.
