How to ensure greater efficiency with electric motors
The first industrial electric motor was probably considered a breakthrough in its day, even when there was much room for improvement. As technology has advanced, motor manufacturers have developed better motors …
The first industrial electric motor was probably considered a breakthrough in its day, even when there was much room for improvement. As technology has advanced, motor manufacturers have developed better motors that use less energy and reduce costs.
While it is natural for manufacturers to employ the latest technology in the creation of electric motors, they have been the best in production methods who have been instrumental in improving the efficiency of these motors.
Consider the following statistics:
- The global electricity market was valued at more than $70 billion in 2015 and is expected to grow at a compound annual growth rate (CAGR) of 4.2% from 2017 to 2025.
- The world’s electricity use is estimated to reach 35 trillion kilowatt hours by 2035, and nearly 28% will be used by electric motors.
- Ninety percent of the installed motors run continuously at full speed and use mechanical systems to regulate output power.
The future looks promising!
Before entering into the efficiency of electric motors, it is important to understand more about the motors commonly used in industries.
A simple DC motor converts direct electrical current into mechanical energy. It is usually equipped with a high number of coils, which make it efficient.
However, it can result in a large amount of wasted energy due to friction between the switch and the brushes, as well as loss of torque at certain angles.
On the other hand, if the motor gets stuck when trying to lift a heavy load, the rotor coils can easily overheat and melt. This is why many heavy industrial appliances use electric motors.
How can manufacturers save electricity with electric motors?
The shape of an electric motor is designed and the way it is used are the two determining factors that can help save electricity. Let’s look at the design aspect first.
The use of copper in stator coils
As far as the conductivity of the motor is concerned, it is always better to go for copper coils rather than aluminium coils. This is because the conductivity of aluminium is lower than that of copper.
To keep up with copper coils, aluminum magnet cables may need larger cross sections to provide the same level of conductivity. Aluminum wire windings may have a higher volume compared to a copper wire motor of the same size.
If you are still using aluminum windings, make sure the ends of the aluminum magnet wire are connected properly. Aluminum oxidizes much faster than other metals, and if aluminum powder is exposed to air, it will completely oxidize in a few days and leave behind very fine white powder.
To make a proper connection that guarantees good conductivity, the oxide layer of the aluminium magnet wire must be perforated to prevent the aluminium from coming into additional contact with the air.
Achieving the highest motor efficiency is more than just deciding between the aluminium and copper windings. Several manufacturers have developed high-pressure crimp connectors to allow for greater efficiency. This has been done to help the aluminum windings keep pace with their copper counterparts.
While it is possible for motors with aluminum windings to reach the power of copper windings, it takes time and money. Aluminum also requires more turns and a larger diameter wire, which may not always be more economical.
If the motor is required to work occasionally or for short durations, and not when efficiency and volume are of the essence, the use of enamelled aluminium wires may make sense. Otherwise, copper windings should always be preferred.
The use of copper bars on the rotor
When it comes to rotors, copper offers the efficiency advantage. Copper rotors are preferred for industries focused on better energy management, in developed and developing countries where electricity is often scarce and expensive.
Copper rotors are a better bet compared to aluminium in terms of motor quality, reliability, cost, efficiency and service life.
Precision Machining for Moving Parts
Machining involves the removal of material from another part to a minimum tolerance. Precision machining is absolutely necessary to achieve the required tolerance.
Whether it’s metal cutting or coal mining, precision machinery can provide the accuracy needed to produce materials in the desired quantities.
Moving parts of the machine will require timely maintenance for maximum performance and efficiency. Maintenance should only be performed by experts, and an inspection of all parts should be required.
The use of high quality steel for rotors and stators
High-tech electric steel is essential for the manufacture of economical stators and rotors used in a variety of electric motor applications. This type of steel ensures high magnetic permeability and low power losses and first class performance.
However, power losses can still occur in electrical steel. Eddy currents come into play when a magnetic field alternates. Lamination of steel to a finer gauge controls these eddy currents and reduces current losses. This happens especially at application frequencies beyond the standard of 50 or 60 Hz.
Keep the rotor and stator as close as possible.
Through precision manufacturing, manufacturers can keep the rotor and stator as close as possible without touching each other. When the rotational speed reaches several thousand revolutions per minute, the electrical steel in the rotor can experience tremendous stress. High voltage is especially felt in areas near magnet slots, where the equipment holds the magnets in place.
With induction motors, energy transfer takes place through the air space between the stator and the motor, the air space is necessary to minimize resistance. A small air space will lead to less energy loss and greater efficiency.
The total flow link between the stator and rotor widens as the air space decreases. A better flow link results in decreased energy losses and increased efficiency. A smaller tolerance also helps prevent noise.
More coils = more efficient motors
The cables of the phase coils of small power motors are thinner, however, the number of turns must be greater to increase the magnetomotive force or current density. The resistance of the phase windings and the density of the power loss are also higher than in high power motors.
Therefore, low power motors with high speeds require more magnetomotive force. This means more coils will be required along with a greater number of turns with a thin wire producing a higher current density.
The use of variable speed controls
Variable speed drives (VSDs) or variable speed drives are heavy industrial electric motors. Their speed can be adjusted with an external controller. These units are used in process control, as they help conserve energy in plants that use numerous electric motors.
VSDs are typically used as energy savers in pumps and fans, as they improve process operations, especially when flow control is required. They also provide soft start capabilities that reduce the electrical stresses and line voltage dips typically encountered when starting a motor, especially with high inertia loads.