The DC vs. AC motors debate has been going on for years. When buying a motor, people often wonder whether AC or DC is preferable, but the answer is that it depends on the application and cost. Using the proper motor with high-quality parts and performing regular maintenance keeps your facility running smoothly and protects endpoint equipment from wear and power spikes.
This article will teach you the fundamentals of electric motors, as well as the many types and how to choose the right one.
What is an Electric Motor?
Electric motor is a machine which converts electric energy into mechanical energy usually by employing electromagnetic phenomena. . It works on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose magnitude is determined by F = BIl Newton and whose direction is determined by Fleming’s Left-hand Rule.Â
The various types of electric motor differ in the ways in which the conductors and the field are arranged and also in the control that can be exercised over mechanical output torque, speed, and position. The following are the two main types of electric motors:
- AC motors, which are powered by alternating current
- DC motors, which are powered by direct current
. Electric motors are available in a wide range of sizes and types. These motors can be selected based on their functioning, voltage, and applications.
How Electric Motors Work
An electric motor is a device used to convert electricity into mechanical energy which is opposite to an electric generator. The field winding and the armature winding are two key components of every motor. The field winding’s primary role is to generate a fixed magnetic field, whereas the armature winding resembles a conductor organised within the magnetic field. They work on the basis of electromagnetism, which states that when an electric current is present in a magnetic field, a force is applied. This force produces a torque on the armature winding in the magnetic field, which causes the armature on the rotor or stator to rotate around the shaft.
Main Motor Components
A simple motor has the following parts:
- A power supply – mostly DC for a simple motor
- Field Magnet – could be a permanent magnet or an electromagnet
- An Armature or rotor
- Commutator
- Brushes
- Axle
Components-In Detail
- Power Source: A basic motor’s power source is usually a DC power supply. It provides electricity to the armature or field coils of the motor.
- Commutator: It is the rotating interface of the armature coil with a stationary circuit.
- Field Magnet: By virtue of Fleming’s left-hand rule, the magnetic field helps to produce a torque on the rotating armature coil.
- Armature Core: The armature coil is held in position and mechanical support is provided.
- Armature Coil: It aids the motor’s operation.
- Brushes: It is a device that conducts current between stationary wires and moving parts, most commonly the rotating shaft.
Types of Electric Motor:
What is a DC Motor?
In DC Motors,Direct current electric energy is converted into mechanical rotational energy. You can also utilize the device in reverse to generate DC electrical power by turning a motor shaft (making the device function as a generator). The winding connections, in which how the two coils in the motor are coupled to each other, can be used to classify DC motors.
The different types of DC motors include DC shunt motor, separately excited motor, series motor, PMDC motor and compound motor.
What is AC Motors?
An alternating current is required for the AC motor to rotate. Using electromagnetic induction, this motor transforms alternating current to mechanical power. Magnetic fields generated by coils wrapped around the output shaft provide energy to an AC motor. A stator and rotor are two elements that make up an AC motor. AC motors are efficient, long-lasting, quiet, and adaptable, making them a suitable option for a variety of power generation applications.
Synchronous and induction motors are the two types of AC motors. There are two types of induction motors: polyphase and single phase. Hysteresis and Reluctance motors are two types of synchronous motors.
What’s the Difference Between AC and DC Motors?
The Magnetic Field
The stator coils of AC motors are subjected to an alternating current, which causes them to produce a rotating magnetic field (RMF). As a result of Faraday’s induction law, the RMF generates an electromagnetic field (EMF). Induction motors, on the other hand, have a higher synchronous speed than the rotor speed.
A non-rotating magnetic field is created by a set of coils or a permanent magnet in DC motors. The armature coils get all of the electricity, causing them to rotate.
Speed Control
In DC Motors, the current and voltage applied to the windings or armature coils determine the speed of DC motors. The device’s speed can be controlled by adjusting the current flowing into the field coils. DC motors have a proportionate speed-current relationship as a result.
Whereas in AC Motors,The alternating current frequency applied to the stator coils of AC motors controls their speed. If a result, as frequency rises, so does speed, and vice versa. The speed and current have a direct proportional relationship.
Performance
DC motors are crucial when you need speed control while AC motors are excellent when you need variable torque and high speed. However, note that the DC motors produce a stable and constant torque over different speed ranges compared to AC motors.
Ac motors experience the slip and induction current loss, thus suffer from efficiency problems. DC motors, on the other hand, are 30% more efficient because they use permanent magnets. Equally, note that DC motors don’t need to create an electromagnet by consuming power.
Startup Mechanism
Polyphase AC motors are self-starting and do not require any additional electronics in order to function properly. DC and single-phase AC motors each require a start-up system that regulates the conditions. To avoid burnout we have to regulate the first ramp-up input voltage while starting a large DC motor.
Input Power
A DC power source will provide a DC motor with a unidirectional current (no change in direction over time). AC motors, on the other hand, are powered with alternating voltage and current that changes in direction and amplitude once a wavelength is complete. The AC motors, therefore, can operate with a polyphase source or a single-phase source.
Which Motor Is More Powerful: AC or DC?
AC motors are typically thought to be more powerful than DC motors because they can create more torque with a higher current. DC motors, on the other hand, are more efficient and make better use of their input energy. AC and DC motors are available in a variety of sizes and strengths to satisfy the power requirements for any application.
AC Motor vs. DC Motor Advantages
Each motor type has its own set of benefits that make it ideal for a variety of commercial and industrial applications. AC motors, for example, are versatile and simple to use. The following are some of their other benefits:
- Low startup power demands that also protect components on the receiving end
- Controllable starting current levels and acceleration
- VFD or VSD add-ons that can control speed and torque at different stages of use
- High durability and longer life spans
- Capabilities for multi-phase configurations
- Controlled starting current
DC motors also offer their own advantages, such as:
- Simpler installation and maintenance
- High startup power and torque
- Fast response times to starting, stopping, and acceleration
- Availability in several standard voltages
AC Motor vs. DC Motor Disdvantages
AC MOTOR:
- The starting torque of this motor is very less
- At low speeds, it won’t operate
- Poor positioning control
- Limited speed through the frequency supply
DC MOTOR:
- The initial cost of a DC motor is high.
- Due to the existence of brushes and a commutator, maintenance costs are high and operation is increased.
- Due to sparking at brush DC motors cannot operate in explosive and hazardous conditions.
- As the speed increases, the shaft gets vibrated and the armature gets damaged.
- We need converters to supply power to the motor
Applications:
Both AC and DC motors find application in processes and facilities in almost every industry. Some of the most common industrial applications for AC motors include:
- Appliances
- Compressor drives and systems
- Computers
- Conveyor systems
- Fans and air conditioners
- Hydraulic and irrigation pumps
- Transportation equipment
Common industrial applications for DC motors include:
- Fabrication and production units
- Machinery that demands constant power such as vacuums, elevators, and sewing machines
- Warehouse sorting equipment