Universal Motor: An Overview of Design, Types and Working Principle

A universal motor is a type of electric motor designed to operate on both direct current (DC) and alternating current (AC). The term “universal” highlights its ability to function with either type of electrical power supply, making it a versatile choice for various applications.

Universal Motor Diagram

The construction of a universal motor shares similarities with a series-wound DC motor, but it incorporates modifications for AC power compatibility. Key components include a rotor (armature) and a stator. The rotor is the rotating part, while the stator remains stationary.

The diagram below illustrates the components of a universal motor.

The universal motor diagram typically shows:

• Stator: The stationary part containing the field windings.
• Rotor (Armature): The rotating part with armature windings.
• Commutator: A rotary switch that reverses the current direction in the armature windings.
• Brushes: Conductive elements maintaining electrical contact with the commutator.
• Power Supply: The external voltage source, either DC or AC.

Universal motors find common use in applications demanding compact, lightweight motors with high rotational speeds, such as power tools, vacuum cleaners, blenders, and certain household appliances. Speed control is easily achievable by adjusting the voltage or utilizing external control devices.

Universal Motor Working Principle

A crucial aspect of the universal motor is the series connection of both the field winding (stator component) and the armature winding (rotor component). This configuration enables operation with either DC or AC power. When connected to AC, the alternating current in the field and armature windings allows the motor to generate torque and rotate.

Upon voltage application (DC or AC), current flows through both the stator and rotor windings, creating interacting magnetic fields that produce rotational motion. The commutator, a rotary switch on the rotor, reverses the current direction in the armature windings at appropriate intervals, ensuring continuous rotation.

Universal Motor Types

Universal motors can be categorized based on design and application characteristics. Here are some common types:

1. Series-Wound Universal Motor
2. Compounded Universal Motor
3. Separately Excited Universal Motor
4. Permanent Magnet Universal Motor
5. High-Speed Universal Motor

Conclusion

Universal motors provide advantages like a high power-to-weight ratio and speed control capabilities. However, they can generate more noise and may have a shorter lifespan compared to some other motor types. Additionally, they may not be as energy-efficient as certain specialized motors in specific applications.