A Complete Guide to Electric Motors

The basics of electricity and its driving devices are essential for any electrician, whether a DIYer or a professional. Electrification and magnetism are combined to create electromagnetic forces that trigger electric motors to generate mechanical energy. To gain a deeper understanding of electric motors, read this article.

What Are Electric Motors? A Short History

Electric motors have revolutionised modern human society’s framework, accredited by Michael Faraday’s law of electromagnetic induction. For almost 200 years, electric motors have been widely used in multiple markets because of their robust applications. By definition, electric motors are electromechanical devices that transform electrical energy into mechanical energy due to their built-in, crucial components for powering electrical equipment. These durable devices use electromagnetic force to drive mechanical energy, produce rotational force, and are integral components for multiple industrial, commercial, and domestic applications.

Electric motors come in varied configurations and sizes that fit vehicles, toys, and other electronic devices. These powerful devices have become an integral part of around 45% of global usage in electric vehicles, and 70% of energy is used in industrial markets. Several electric motor suppliers across different countries market these durable and functional products for global users with user-desired applications. Functional designs, compact sizes, high efficiency, low power consumption, and reduced costs are some of the benefits of electric motors used in everyday and industrial settings.

The Working Principle or Physics of an Electric Motor

Electric motors follow simple principles for converting electrical energy into mechanical energy, triggering them to create motion. By following Ohm’s law, the force within electric motors increases with an increase in AC/DC by interacting with a magnetic field. In simple words, the magnetic field increases by increasing the current’s strength. Different components within a motor trigger the production and consistent flow of a magnetic field.

Mechanical Principles of an Electric Motor

As per the hyperphysics rule, force generation is directly proportional to the introduction of an electric current that produces a magnetic field. The built-in looped wires within an electric motor carry current, stationed in magnetic fields at right angles. Due to the dual polarity of the magnetic field, each wire end moves in an alternate direction, resulting in turning momentum. There are different ways to control the torque and magnetic field with an electromagnet and keep the electric motor operating for extended periods without any damage.

Key Parts of Electric Motors

Electric motors are comprised of key components that work in combination for effective applications. A typical or commercial motor consists of the following key parts, each with specific functions.

• Bearings – Bearings are the supporting materials for the rotor and casing/body of electric motors and minimise friction. They are made from materials that feature minimal friction, such as aluminium. These rotor- and shaft-supporting bearings are extremely robust and strong, with reduced resistance. The efficiency of bearings depends on the load, design, and environmental factors and is used to minimise energy losses.

• Rotors – Rotors are the fundamental parts of electric motors that transform electric energy into mechanical energy. Rotors are available in various designs, providing consistent torque. The latest-designed rotors incorporated in an electric motor are capable of producing maximum torque without any interruption.

• Stators – are the stationary components of electric motors that are made of metallic sheets or laminated cores to reduce energy losses. They feature either a fixed magnet or windings.

• Armature – located on the stator or rotor part of the electric motor, an armature is the energy-producing component with wire coils that interact with magnetic fields when electric current flows through them.

• Commutator – Commutators are switching components of electric motors that reverse the current direction in DC motors (less in AC motors).

• Air Gap – To our surprise, air gaps are not considered components of electric motors; they are, however, the crucial parts occurring between the device’s parts. Air gaps are used for electromagnetic induction and are compact. The smaller the air gap, the better the electric motor will perform.

• Carbon Brushes – Also known as motor brushes, are motor miniature parts made of one or more carbon blocks that allow electrical current to be transmitted between rotors and stators. These carbon brushes are available with terminals or shunts that conduct electric current as they rotate.

• Windings – In electric motors, windings are coiled conductive wires typically surrounding a metallic magnetic core designed to provide a current flow path for producing a magnetic field. The resultant magnetic field then spins the rotor, thus creating momentum.

• Frame or Casing – The frame or casing of an electric motor effectively protects the device’s internal and external parts from physiochemical factors of the environment. The frame is made of lightweight materials (like aluminium) and is regarded as the protective boundary for mitigating the parts of electric motors, such as rotors and stators, from temperature, humidity, and other challenging environmental conditions. They are also rust-resistant, depending on the materials used.

• Shaft – The shaft is the extruded cylindrical component in an electric motor that connects all the rotating parts of the motor for the conversion of energy for end-use applications. Mostly, the shaft is designed to make contact with the motor’s bearings for a rotor carrier that rotates efficiently with minimal friction. The metallic shaft is extruded from the device’s housing for transmitting mechanical energy to end-load applications.

• Cooling Fan – As the name indicates, the motor is equipped with cooling fans for consistent motor cooling applications. Depending on the motor type, different cooling fans are attached to the motor’s rotors for the purpose of providing increased airflow to its internal and external parts as they spin with the motor.

Easy Electric Motor Installation: Things to Require

While you can install your motor types by yourself, it is crucial to consult a qualified professional for a smooth project and to avoid injury. When mounting or replacing, ensure to mount or properly install for longer service life. For a bespoke project, you would need different tools depending on the motor types. The tools include drills, screwdrivers, wrenches, torque wrenches, screws and bolts, electric screws, and many more.

Types of Electric Motors

With two basic types, electric motors can be broadly classified into various types, as illustrated in the diagram.

Induction Motors 

Induction motors or asynchronous motors are the most common alternating current electric motors that operate at higher speeds. These motors rely on and operate on the principle of producing the magnetic field of the stator rather than the rotor’s torque. The name “asynchronous motor” comes from the fact that they operate at a lower speed than their synchronous counterparts, which is the rotation speed of a magnetic field in a rotating machine. Induction motors are widely used in conveyors, hoists, elevators, crushers, compressors, and other load applications that require speed control. Single-phase and three-phase induction motors are the two types of induction motors based on the phases.

• Single Phase Induction Motor – These motors are designed to change single-phase AC power into mechanical forms by using the phenomenon of electromagnetic induction, where a rotating magnetic field induces electric current across an electrical conductor. These motors are mostly found in domestic appliances such as fans and other smaller loads.
• Three-phase Induction Motors – These motors convert three-phase alternating current power into mechanical energy induced by a magnetic field. They are extensively used in AC motors for the mechanical power generation industry and other domestic applications.

DC Electric Motors

DC motors are electric rotary machines powered by DC that are designed to convert electrical power into mechanical power output. These motors produce a magnetic field (mechanical rotation) in the stator by providing a power source. They are widely used in elevators, vehicles, rolling mills, conveyors, and other applications that require adjustable and low-speed torque. DC motors are further divided into separately excited and self-excited motors.

Separately Excited DC Electric Motors

These motors are energised and get their DC windings excited by a separate DC source, thus producing a flux. Their built-in field circuits (armature windings and fields) are supplied from a separate power supply (constant voltage) by using a field coil for stationary magnetic field generation. They are extensively used in trains as actuators and in automotive traction systems.

Self-Excited DC Motors

Self-excited motors with a single power source are excited by the power they produce. These motors boast field coils and armatures connected in parallel or partially parallel, in series/partly in series. Self-excited motors are classified into three types based on their field winding connection.

Other Electric Motor Types

Besides the abovementioned motors, other electric motor types are available on the market with unique specifications. These motors include:

Stepper Motors

Stepper motors, also called stepper or stepping motors, are high-precision DC electric motors that operate by stepping from position to position without consistency. These motors stop each time they reach a new position and operate in sequences due to their organised multiple coils, called phases. Due to their forward or backward movement, they are easily controlled by providing a feedback mechanism. The motor’s sequential and discontinuous operation sets it apart from the rest of the electric motors on the market. Stepper motors are extensively used commercially in various devices and consumer products, such as 3D printers, image scanners, plotters, computer printers, disc drives, CNC machines, and flatbed scanners. 

Servo Motors

Servo motors are electric motors or devices with a closed-loop system that provides feedback due to a built-in feedback device. They are all-in-one devices known for their high precision and positioning applications in various industrial markets. The motors are designed to push or rotate machinery parts with extreme accuracy. Servo motors are easy-to-control, smooth-running, compact, and highly reliable machines extensively used in food processing, robotics, printing, machine tools, pharmaceutics, elevators, and the defense sector.

Waterproof Electric Motors

As the name suggests, waterproof electric motors are machines that operate underwater, even under extreme conditions. They are widely used in industrial environments with varying water depths due to their waterproof capabilities. Waterproof motors are extremely resilient to a standstill, highly efficient, and provide high torques. They consume less energy and are economical with sea-water resistance. Depending on the motor types, they can withstand water depths up to 40 meters. 

Robotic Motors

Robotic motors are lightweight and powerful electric motors designed to power robotic equipment with high efficiency. They are easy to maintain and feature reduced noise and zero emissions. Depending on the users’ requirements, robotic motors provide movement mechanisms and can drive robots around by attaching them to the robot wheels. Robotic motors are widely used in a wide variety of robots. In portable and industrial robots, brushed and brushless DC motors are used, whereas permanent magnet DC motors are popular.

Special Magnetic Motors

Magnetic motors, also known as magnet motors, are specialised motion machines that use permanent magnets in the stator and rotor to generate rotational force without utilising an external power supply. Numerous hobbyists advocate this idea, both practically and theoretically; however, it remains a parascience and is unrealisable. These motors are sometimes used interchangeably with common permanent magnet motors; however, this is not the case. Permanent magnet motors operate by using an external energy supply. 

Electric Motors for Toys

Electric motors for toys are DC motors that are widely used in toys, tools, and other consumer appliances. Depending on the motor type, they are made from plastic or metallic materials with exceptional durability and strength. The speed of bespoke DC motors is controllable by changing their windings’ current or using variable supply voltage. Small DC motors are widely used in a variety of electronic and hobby devices, such as cars, airplanes, boats, toys, hand tools and fans . There are multiple DC motor manufacturers for toys on the market with an extensive range of products for educational, DIY toys, cars, and other scientific projects. 

Electric Clock Motors

Electric clock motors are miniature electric motors designed to provide motive force for proper clock functionality. These motors are coupled to the clock, driving reduction gearing at a precise rate with little power. The most recent electric wall quartz clocks use small stepping motors to convert electric input into mechanical output and drive seconds increment. There are a variety of different electric motors used in electric clocks, including:

• Lavet-type stepping motors, used in electro-mechanical clocks.
• Synchronous motors, used in clocks or timers.
• Impulse motors, used in pendulums.
• Miniature stepping motors, used in watches and quartz clocks.

Marine Electric Motors

Electric marine motors are high-efficiency, high-power-density motors designed for marine use. These motors operate at lower temperatures in a variety of boats and ships. Marine electric motors do not produce loud noises and run smoothly. In most ship machinery systems, induction motors are used, including miniature synchronous motors, blower motors, pump motors, propulsion motors, and crane motors that can withstand liquid environments. Marine electric motors include various types, such as:

• Electric motors for yachts
• Electric motors for houseboats
• Electric motors for sailors
• Electric motors for ships
• Electric motors for leisure boats.

The Difference Between AC and DC Motors

AC and DC motors are distinguished based on their current types, efficiency, and phase configurations. AC motors use alternating current for energy, whereas DC motors utilise direct current. A further difference lies in their speed, where high efficiency and increased output are the attributes of AC motors, while DC motors are known for their output range and speed control. Furthermore, DC motors are only available in single-phase configurations, while the others come in single- and three-phase configurations. Last but not least, AC motors can be driven over longer distances, which is more energy efficient than DC, which is restricted over long distances and loses efficiency.

Differentiation of Electric Motors Based on Phase

For effective applications, electric motors are also classified based on their phase power supply. These include:

Single Phase Electric Motors

Single-phase motors transform electrical energy into mechanical energy by using a single-phase power supply and producing power up to 10 hp (horsepower). These electric motors have limited torque capacities and feature two wires. These are compact and utilise a single AC voltage that typically requires a capacitor for startup. 

Three Phase Electric Motors

Three-phase motors convert electrical energy into mechanical energy by using a three-phase power supply and producing up to 400 hp. They achieve considerably high speeds, ranging from 900 to 3600 RPM (rotations per minute), and comprise four wires. Three-phase motors, as opposed to single-phase motors, use three identical-frequency alternating currents, and do not require capacitors for starting operations because they generate rotating magnetic fields. Additionally, bespoke motors can also serve as generators that convert mechanical energy into electric energy. 

Series and Parallel Motors: The Difference

Series motors are DC motors with a high starting torque and two series windings with a similar current. These motors are extensively used in demanding applications where high speed is indispensable, such as elevators, trains, and hoists. They are also effective for dragline excavators that, when unloaded, move rapidly while having heavy loads, moving slowly. In contrast, parallel motors are suitable for high-velocity applications that maintain torque at a higher velocity, though at a lower speed than series motors. Wiring in parallel produces four times the resistance and inductance of wiring in series, which results in more current and heat.

What is the RPM of a Motor?

RPM (rotation per minute) is a motor’s measurement that refers to the speed of the motor, or the rotating speed of the motor. Basically, it describes the number of times the rotor shaft completes or revolves a full rotation per minute. It is the basic criteria for ascertaining the speed measurement of various equipment, such as turbines, conveyors, and centrifuges, for required monitoring and controlling applications. It is also crucial for selecting the right motor type for repair and replacement applications. 

What is the Efficiency of a Motor?

The efficiency of the motor refers to the performance of the device and is the ratio between its input and output ranges, represented as “%” and denoted by the symbol “η”. Basically, efficiency informs us about the motor’s performance and is the ratio between input & output power at the motor shaft. The efficiency of the motor can be enhanced by reducing the motor’s losses, which are affected by various parameters, such as mechanical losses, resistance losses, and magnetic energy dissipation losses. 

Common Watts and Dimensions of Electric Motors

Mostly, the wattage or motor power is provided with the device, for instance, 12 V electric motors. However, it is easy to calculate the given wattage of your device. For estimating the motor’s horsepower quickly, use measuring tools such as a clamp meter for determining the motor’s voltage or current. For manual calculations, simply multiply motor voltage (V) by current (A), which results in output power. For instance, for a motor running at 30 V and 6 A; its resultant output power will be 30 V x 6 A = 180 W. Regarding the motor’s dimensions, there are standard horsepower ratings for electric motors ranging from 1 to 4000 hp. Some of the common electric motors with their voltages are given as under:

• Servo Motor, 7.5 kW, 400 V.
• Three-phase induction motor with 115V, 230V, 460V, 575V.
• Single-phase motors with 115V, 208V, and 230 V.
• Asynchronous motors up to 13.8 kV.
• Reversible Synchronous AC Motor, 110 V.
• High-voltage slip-ring motors with power up to 15000 kW.
• High-Voltage squirrel-cage motors with power up to 25000 kW.
• HV motors up to 13800 Volts.
• Squirrel Cage Motor AC motor with 1,5 kW, 230V, 400V, 415V.
• Servo Motor, 1 Phase, 230 V.
• DC Motors with 120 and 240 volts.
• Small electric motors 240V.
• Induction AC Motor, 230 V, 400 V.
• DC Motors with 230 and 440 volts.

Choosing the Right Electric Motors Type

Though a huge variety of electric motors are available on the market today, it is often confusing to select the right motor for your applications. It is crucial to ascertain several important parameters before buying a specific motor, including:

• Motor Type – Considering the right type of motor is the foremost factor when selecting a motor for your desired applications. Of the various motor types, choose the exact motor type that suits the environment and applications. 
• Voltage – Consider the required voltage for motors in your applications. For instance, choose the voltage requirements for DC motors to run at an efficient voltage. Applying the recommended voltage is essential for smooth operation and avoiding damage or power loss. 
• Configuration Designs – Electric motors come in varied configurations, i.e., single-phase, or three-phase configurations. For optimal performance, determine your specific motor configurations.
• Applications – Each motor suits specific applications, and it is important to verify the desired applications of your specific motor type.
• Size – The size of the electric motor is also important because it represents the space occupied by the motor and how it will be mounted on the system.
• RPM/Speed – Speed, velocity, or RPM is a crucial factor when considering a specific motor for your applications. High speeds do not correlate with the device’s efficiency, especially when gearing is needed. Consider the RPM of the motor before buying your desired motor. 
• Environment – Choosing the typical environment is vital because the motor types determine the suitable type of environment, such as waterproof, industrial, shock-resistant, high-temperature, or corrosive.
• Load of the Motor – Selecting the right motor that can hold specific loads in industrial, commercial, or domestic applications.
• Power/Current – Choose the motor type that has the required amount of current to avoid any damage. The maximum amount of current can damage the motor and melt the motor’s built-in coils. For instance, check the operating power for DC and AC motors at typical torque. 
• Operating Torque – Choosing a motor with a fixed amount of operating torque and speed is also crucial. Different motors are designed to operate at different torques, such as high torque low speed electric motors. The resultant torque triggers the device’s performance for particular applications to handle the weight or loads. 

Best Electric Motor Market and Accessories

Enrgtech is one of the biggest electronic and electrical product suppliers in the UK that houses robust electric motors and their accessories. Motor accessories are essential components required to complete the motors’ assembly for their proper functionality. Enrgtech stocks branded motor controllers, motor starters, inverters, and motor accessories that include connectors, cables, adapters, and many more for use with servo and drive motors and other motor series. The company also carries electric motors’ peripherals, including motor protection circuit breakers, motor protection accessories, DOL & Star Delta starters, gearboxes, and linear actuators, at economical rates.   

Safety Considerations for Electric Motors

Electric motors can cause serious injuries in various settings and are prone to electric shocks and fires. To avoid these risk factors, there are certain concerns, safety practices, and precautions that need to be taken, including:

• Always consult with experts when deploying motors or moving parts to avoid injury.
• Do not open or wind the motor if you are not a professional.
• Use safety goggles and gloves for protection to avoid personal injury.
• Short-circuit or damaged motors should not be touched.
• Ensure proper motor inspection before operation.
• Use the recommended voltage for the motor type you want.
• Do not use short-circuited or damaged batteries to avoid their explosion. 
• Avoid leaving motors unattended and keep children away.
• Remove plugs or power sources when motors become hot and cause fires.
• Avoid using motors in flammable, wet, or explosive environments. 
• Remove all wires before inspecting or touching motors.
• Shut down the device during any faults or unusual operations.
• If possible, provide fuse protection circuits to avoid injury and electric shocks.
• Always use a particular motor for specific applications.

Top Ten Electric Motor Manufacturers in the United Kingdom

In international markets, electric motor manufacturers are in greater demand because electric motors are frequently used in everyday applications and industrial markets. Within the UK, Enrgtech stocks an extensive collection of different electric motor types from the leading manufacturers in the world. Among the top manufacturers, WEG electric motors, parvalux electric motors, Clarke electric motors, and Tesla electric motors have a leading position and are distributed across different regions worldwide. Enrgtech ranks over other manufacturers due to its speedy delivery, guaranteed quality, and reduced product costs. Among the leading market specialists and suppliers for electric motors include:

• Bosch
• AEM (Advanced Electric Machines)
• Mini Electric Motor
• Tec Motors
• Remco
• AC Electric Motor
• ABB
• T-T Electric
• Siemens
• Amtecs.

Applications of Electric Motors

Electric motors are extensively used in industrial, commercial, and domestic settings in different ways. They have become integral parts of various industrial and residential markets due to their compact size, designs, durability, efficiency, and functionality. Some of their effective applications in bespoke fields include:

FAQs

1. What should I do if an electric motor burns out or overheats?

Overheating an electric motor reduces its lifespan, resulting in the deterioration of its winding insulation and bearings. Overheating is the result of excessive current flow that can burn an electric motor. If the device is overheating, remove the power source and ensure the ventilation holes are clear enough, as practically, the motor cannot be repaired. 

2. Is it possible for electric motors to be waterproof?

In the majority of cases, electric motors are not waterproof due to their respective applications and environments. However, there are waterproof electric motors designed for particular underwater applications. For instance, waterproof motors are used in pool cleaners, pumps, and off-road vehicles that require motor exposure to liquids. 

3. What are the parts of a simple electric motor?

With three basic parts-a rotor, a stator, and a commutator-other parts of a simple electric motor include an axle and a power supply. 

4. What are the benefits of electric motors?

Of the various benefits, high efficiency, durability, compact size, reduced costs, and low maintenance are remarkable benefits of electric motors.

5. Are there any other types of electric motors?

Aside from the electric motors mentioned above, the market also has cooling tower motors, brake motors, generator motors, agricultural motors, air compressor motors, electric motors for motorcycles, crusher duty motors, instant reversing motors, and repulsion motors.