A universal motor is a type of electric motor that is capable of running on both AC (alternating current) and DC (direct current) power sources. It is called a “universal” motor because it can be used in a wide range of applications, including both domestic and industrial use.
Construction of universal motor:
The construction of a universal motor is similar to that of a DC motor. It consists of a stator (stationary part) and a rotor (rotating part). The stator typically consists of laminated steel cores with slots to hold the windings. The rotor contains a commutator and brushes, which make contact with the commutator. The rotor windings are wound around the laminated steel cores.
Working of universal motor:
The universal motor operates on the principle of electromagnetic induction. When an electric current flows through the windings, it creates a magnetic field that interacts with the field produced by the permanent magnets or electromagnets in the stator. The interaction between these magnetic fields causes the rotor to rotate.
In AC mode, the direction of current in the windings changes periodically, causing the magnetic field to alternate. The brushes and commutator help in reversing the direction of current in the rotor windings, allowing the motor to run on AC power.
In DC mode, the current flows in one direction only, and the commutator and brushes help in maintaining the direction of the magnetic field and rotor rotation.
Types of universal motor:
- Series Universal Motor: In this type, the field windings and armature windings are connected in series. It provides high starting torque and is commonly used in applications requiring high power, such as vacuum cleaners and power tools.
- Shunt Universal Motor: Here, the field windings and armature windings are connected in parallel. It offers a more constant speed characteristic and is often used in applications like blenders and food processors.
Advantages:
- Wide power supply compatibility: Universal motors can run on both AC and DC power sources, making them versatile for various applications.
- High power-to-weight ratio: Universal motors have a high power output relative to their size and weight, making them suitable for compact devices that require high performance.
- High starting torque: Universal motors provide high torque at startup, making them ideal for applications requiring initial heavy loads.
Disadvantages:
- Limited efficiency: Universal motors are generally less efficient compared to specialized AC or DC motors, leading to higher energy consumption.
- Higher maintenance: The brushes and commutator in universal motors wear out over time and require periodic replacement, resulting in increased maintenance needs.
- Electromagnetic interference: Universal motors can generate electromagnetic interference (EMI) due to the brushes and commutator, which can affect other electronic devices nearby.
- Shorter lifespan: The combination of high speed, friction, and mechanical wear in universal motors may result in a shorter operational lifespan compared to other motor types.
Applications
- Household Appliances: Universal motors are commonly found in household appliances such as vacuum cleaners, blenders, food processors, and electric mixers. These appliances require high rotational speeds and the ability to operate on both AC and DC power sources.
- Power Tools: Universal motors are widely used in power tools like drills, circular saws, routers, and electric screwdrivers. Their compact size and high power-to-weight ratio make them ideal for handheld tools.
- Hair Dryers and Electric Shavers: Universal motors are used in hair dryers and electric shavers due to their ability to provide high-speed rotation for airflow or blade movement. These motors can operate on both AC and DC power, making them suitable for use in various countries.
- Portable Equipment: Universal motors are often employed in portable equipment such as portable fans, electric trimmers, and portable vacuum cleaners. Their compact size, lightweight design, and ability to operate on different power sources make them suitable for portable applications.
- Automotive Applications: Universal motors can be found in certain automotive applications, particularly in older vehicles. They are used in windshield wipers, electric fans, and power windows due to their ability to operate on the vehicle’s DC electrical system.