slip ring motor working principle

As we embark on the pathway of technological advancement, a keen understanding of the machinery that drives our progress becomes all the more important. Among the diverse plethora of machines, electric motors play an undeniably critical role. Not all motors are created equally, however, and a question that often arises in engineering circles is the comparative analysis between Slip Ring Motors and Squirrel Cage Motors. This forms the context of our exploration in this article.

The article is meticulously structured to present a comprehensive overview of these two types of motors. We will journey through different aspects, tracing their histories, understanding their functional characteristics, appreciating their key features, and diving into their respective benefits. We will explore the nuances of their functionalities that set them apart, as well as the similarities they share.

A core section of the article will be a detailed comparison between the two types of motors. This head-to-head comparison will cover their design, structural aspects, performance characteristics, cost, and maintenance requirements. It will provide an in-depth understanding of their operational efficiencies, lifespan, speed control, starting torque, and power factor. We will look into how these characteristics influence their suitability for various applications, and the environmental considerations associated with each.

The aim of this article is not merely to provide a dry comparison, but rather to take you on an informative exploration that illuminates the essence of these two motor types. As we delve further into the subject, we wish for you as a reader to develop an intuitive understanding that extends beyond technical jargon and complex mechanical interplays.

This understanding will have practical implications, enabling you to make informed decisions in your respective fields, be it industrial manufacturing, mechanical engineering, equipment procurement, or even academic research. With this context set, let us begin our exploration.

Introduction to Slip Ring Motors

History of Slip Ring Motors

Slip Ring Motors also referred to as wound-rotor motors, trace their origins back to the twilight years of the 19th century. It was a period of profound leaps in electrical engineering, witnessing inventions that would lay the groundwork for modern-day industries. Amidst this backdrop, the Slip Ring Motor took shape, its evolution propelled by engineering visionaries who championed the power of electromagnetism and its innovative uses.

Basic Functionality and Design

The functionality of Slip Ring Motors might seem daunting at first glance, but at its core, it involves fundamental principles of electromagnetism. The motor consists of two primary components: a stationary stator and a rotating rotor. The stator generates a rotating magnetic field when a three-phase AC current is passed through it. It eventually transmits electrical energy to the rotor with the help of the motor’s namesake – the slip rings.

These are rotating electrical connections composed of conductive materials, which provide power to the winding on the rotor through brushes made usually of graphite. As electricity passes through the wound rotor windings, it’s influenced by the magnetic field from the stator, which causes the rotor to rotate and deliver mechanical power.

Key Features and Benefits

Slip Ring Motors has some distinctive features and benefits that have ensured their relevance in the ever-evolving landscape of electric motors. Firstly, thanks to their construction with variable resistance, they can handle high starting torque requirements, making them a suitable choice for applications that require a significant power surge to kick-start operations.

The ability to control and adjust their speed and torque under load is another major benefit. This flexibility allows for greater power optimization based on the specific requirements of an operation, aiding in energy-efficient practices.

Additionally, the changeable resistance presented in its rotor circuit can lead to an improved power factor, which leads to more effective power usage. These qualities provide the Slip Ring Motor with a distinct place among electric motors, proving its worth across a spectrum of heavy-duty applications.

As we delve deeper into the journey of Slip Ring Motors, we make a transition from understanding its past and basic functionality, to appreciating its inherent features and benefits. This sets up a scaffolding of knowledge that aids us as we explore further parallels and distinctions in the world of electrical motors.

slip ring motor working principle

Introduction to Squirrel Cage Motors

History of Squirrel Cage Motors

Squirrel Cage Motors, also known as Induction Motors, owes its existence to the brilliant mind of Nikola Tesla, a pioneer in electrical engineering. In the late 19th century, Tesla invented the first AC induction motor, a transformative addition to the field of electrical engineering. The intriguingly christened ‘Squirrel Cage’ motor draws its name from the unique cylindrical structure of its rotor, reminiscent of the exercise wheel found in a squirrel’s cage.

Basic Functionality and Design

Just like Slip Ring Motors, Squirrel Cage Motors operates based on the principles of electromagnetic induction. However, a striking difference lies in their rotor design. Instead of copper bars or winding linked by end rings, the motor’s rotor is built with a ‘cage’ of conductive bars laid into slots, connected at each end by metallic rings that form a shape akin to a squirrel’s cage.

When a balanced three-phase AC supply is provided to the stator, it creates a rotating magnetic field. This field cuts across the bars of the rotor, inducing an electromotive force, and consequently, an electric current. This current generates its magnetic field that interacts with the stator’s magnetic field, causing the rotor to rotate and, thus, convert electrical energy into mechanical energy.

Key Features and Benefits

Squirrel Cage Motors comes with a portmanteau of features and benefits that make it a popular choice in various applications. Their standout trait is their robustness, reliability, and simplicity of design. They have fewer moving parts with no brushes or slip rings, which results in lower maintenance requirements, a pivotal aspect in many industrial scenarios.

Notably, these motors possess high-speed capabilities and exhibit high efficiency in the conversion of electrical energy to mechanical energy. Additionally, their rugged design makes them highly durable, contributing to a longer lifespan with fewer chances of breakdown or failure.

The absence of brushes or slip rings also lessens the chances of sparking, thereby making Squirrel Cage Motors safe for use in hazardous environments. This suitability across a range of applications, coupled with their overall efficiency and robustness, positions Squirrel Cage Motors as a mainstay in the domain of electrical motors.

In essence, our discussion helps us understand the change of guard from studying one type of motor to another, from the historical underpinnings of the Squirrel Cage Motors to their fundamental workings, and then to their key features and advantages. This time, the context broadens, blending our foundational knowledge of Slip Ring Motors to appreciate the strengths and differences found in Squirrel Cage Motors.

squirrel cage rotors

Key Differences between Slip Ring Motors and Squirrel Cage Motors

As we unwrap the functionalities and intricacies of Slip Ring and Squirrel Cage Motors, we naturally gravitate towards understanding their core differences. By focusing on their structural aspects, performance characteristics, and cost and maintenance requirements, we can better grasp their distinctions and appreciate their unique strengths.

Structural Aspects

The primary structural divergence between Slip Ring Motors and Squirrel Cage Motors lies in their rotor design, particularly their rotor windings. A Slip Ring Motor incorporates a ‘wound rotor,’ which includes slip rings and brushes intentionally added to the rotor assembly for external resistance control. This gives the motors a higher degree of flexibility and control, albeit at the expense of increased complexity.

Conversely, a Squirrel Cage Motor employs a ‘squirrel cage’ rotor – a simple, robust design known for its durability. This design involves shortening the rotor conductors, eliminating the need for brushes and slip rings. This results in less complexity but at the cost of reduced control of speed and resistance.

Performance Characteristics

Performance characteristics stand as another differentiation point. Slip Ring Motors, with their wound rotor, offer high starting torque and adjustable speed control, making these motors ideally suited for high inertia loads or applications requiring high torque for startup.

On the other hand, Squirrel Cage Motors are known for their high operational speeds, efficiency, and reliability, tailored for applications where constant speed is requisite, and lower starting torque will suffice.

Cost and Maintenance Requirements

Cost and maintenance requirements are crucial considerations in any operational setting. Due to their simpler design structure, which involves fewer components and eliminates the need for brushes and slip rings, Squirrel Cage Motors tend to be less expensive and require less maintenance.

In contrast, the intricacies of the wound rotor with slip rings in Slip Ring Motors make them more expensive to purchase and maintain since the additional components require regular inspections and replacements to ensure optimal function.

As we juxtapose these key factors in the context of our narrative, we form a more rounded understanding of both Slip Ring Motors and Squirrel Cage Motors. This understanding goes beyond basic knowledge, assisting us in making informed decisions based on specific application needs and budgets. Over the following sections, we will delve deeper into these differences, increasing the granularity of details to paint an even clearer picture of these motors’ unique capabilities.

Key Similarities between Slip Ring Motors and Squirrel Cage Motors

While the differences between Slip Ring Motors and Squirrel Cage Motors are fundamental to understanding their unique qualities, their similarities draw them together as part of the wider category of Induction Motors. By focusing on their shared operating principles, component similarities, and common use cases, we illuminate the areas where these two types of motors converge.

Shared Operating Principles

Slip Ring Motors and Squirrel Cage Motors both operate on the principles of electromagnetism. They utilize the interaction of a rotating magnetic field with induced currents to deliver torque. This underlying principle of operation, based on Faraday’s law of electromagnetic induction, unites the two motor types despite their contrasting characteristics.

Component Similarities

The basic structure of both types of motors incorporates a stator and rotor. The stator, which is the stationary part of the motor, houses windings that, when energized with a three-phase AC supply, induce a rotating magnetic field. The rotor, which is the rotating part of the motor, is acted upon by the magnetic field to produce torque. Despite differences in rotor design, the presence of these key components exemplifies a fundamental unifying characteristic.

Use Cases Where Either Could be Utilized

Both types of motors have made their way into several industries due to their efficient operation. Common applications include pumps, fans, blowers, and general-purpose industrial machinery. Both types can be used where there is a need to convert electrical energy into mechanical energy, and specific selection between the two is generally based on application-specific requirements like starting torque, speed control, maintenance considerations, and cost.

By appreciating these shared characteristics and common usage scenarios, our exploration of these motors lends itself to a broader understanding. The context weaves a narrative where despite inherent differences, common themes and principles arise. This understanding allows us to fathom more fully the role and application of these motors across a range of industries.

Comparison Between Slip Ring Motors and Squirrel Cage Motors

As we journey further, our knowledge of the two motor types broadens, inviting us to delve deeper into their construction and design aspects. By contrasting the nuances of their design, we clarify the unique features and applications that set them apart even further.

Slip Ring Motors vs. Squirrel Cage Motors: Construction and Design

While both Slip Ring Motors and Squirrel Cage Motors share the foundational components of stator and rotor, the differences in rotor design remain the most distinguishable factor between them, showcasing each type’s unique capabilities.

Slip Ring Motors:

  • The rotor design in Slip Ring Motors consists of three separate windings connected in a ‘Y’ configuration. The free ends of these windings are connected to external slip rings mounted on the rotor shaft.
  • Graphite or metallic brushes, which are in contact with these slip rings, facilitate the passage of electrical energy into the rotor windings. This allows for external resistors to be inserted into the rotor winding circuit.
  • The ability to adjust the external resistance during operation grants the user control over varying speed and torque properties. However, this increased complexity in design raises the need for regular maintenance and monitoring.

Squirrel Cage Motors:

  • The signature design element in a Squirrel Cage Motor lies in its rotor, which is essentially a cylinder of laminated iron cores with short-circuited conductive bars, giving it an appearance similar to a squirrel’s cage.
  • Instead of utilizing external slip rings and brushes, these copper or aluminum bars run the length of the iron cores, and they are short-circuited by end rings.
  • While lacking control over external resistance adjustments, this simplified design leads to higher efficiency, lower maintenance needs, and reduced costs. The Squirrel Cage Motors are designed for applications that demand constant speed and dynamic performance throughout.

In the context of this comprehensive comparison, we uncover the intricate details that set the construction and design of Slip Ring Motors and Squirrel Cage Motors apart. This deep understanding enables us to make informed decisions, ensuring the most suitable motor is chosen based on the specific requirements of a given application.

Slip Ring Motors vs. Squirrel Cage Motors: Efficiency

Understanding the efficiency of these motors involves delving into the transformation of electrical energy into mechanical energy and their overall operational performance.

Slip Ring Motors:

  • Slip Ring Motors tend to be less energy-efficient compared to Squirrel Cage Motors. This is primarily due to the presence of slip rings and brushes, which introduce some energy losses.
  • Furthermore, the ability to adjust the external resistance results in greater control over starting torque and speed, but this advantage comes at a cost: increased energy consumption during operation.
  • In applications that demand high starting torque and continuous speed adjustments, the trade-off between efficiency and functionality becomes more acceptable, justifying the usage of Slip Ring Motors.

Squirrel Cage Motors:

  • Squirrel Cage Motors boasts higher efficiency rates compared to their counterparts. By eliminating the need for slip rings and brushes and employing the simple, robust cage design, they reduce energy losses and promote robust performance.
  • These motors are designed for constant-speed applications, and they perform well in situations where high starting torque is not a primary requirement.
  • As energy efficiency becomes a crucial factor in various industry applications, the inherent efficiency of Squirrel Cage Motors provides a clear advantage.

Taking stock of the context, we see that this comparison of motor efficiencies sheds light on their suitability in different applications. It equips us with even more knowledge to discern the right type of motor for any given scenario and tailor our choices according to the energy consumption requirements and the specific performance needs.

Slip Ring Motors vs. Squirrel Cage Motors: Maintenance Requirement and Ease

The requirement and ease of maintenance are crucial in dictating the lifetime of the motor as well as the resources assigned to their upkeep. Each type of motor, given its unique construction and design, has different maintenance necessities.

Slip Ring Motors:

  • Due to their more complex design thanks to the slip rings and brushes, Slip Ring Motors usually demand more rigorous maintenance. The slip rings and brushes, being subject to wear and tear, require regular inspection and replacement.
  • Additionally, they need periodic cleaning to prevent dust or dirt from interfering with the electrical contacts. The wound rotor also needs regular checks to inspect any deterioration in the winding insulation.
  • While these regular maintenance requirements might add to the overall operational costs, the flexibility provided by a slip ring motor in control of speed and torque can often offset these incremental costs.

Squirrel Cage Motors:

  • Squirrel Cage Motors has a reputation for being low maintenance, which is largely due to its simplified design. The lack of slip rings and brushes reduces the number of components that could wear out or fail, thereby increasing the motor’s overall reliability.
  • Regular maintenance generally involves basic motor practices such as periodic inspection and cleaning, along with checking the bearing lubrication. However, these requirements are relatively low compared to those for Slip Ring Motors.
  • As a result, Squirrel Cage Motors are often favored in applications where regular intensive maintenance is not feasible, or the simplicity and reliability of operation are prime considerations.

In the broader context, our detailed comparison has navigated the intricate pathways of the Slip Ring Motors and Squirrel Cage Motors, offering us rich insights into their unique characteristics. The exploration of their maintenance requirements and ease further equips us to make informed motor selection choices, mapping the long-term resources, labor, and cost implications against the expected performance and application necessities.

Slip Ring Motors vs. Squirrel Cage Motors: Cost-effectiveness

Given their contrasting design constructs and operational characteristics, these two motors present differing cost implications, both in terms of initial capital investment and incurring costs over the motor’s life cycle.

Slip Ring Motors:

  • The more complex design of Slip Ring Motors makes them typically more expensive to manufacture, leading to a higher initial purchasing cost.
  • Additionally, this complexity demands more rigorous maintenance, which contributes to higher ongoing operational costs over the lifetime of the motor. Frequent replacement of components like brushes and slip rings also adds to costs.
  • However, in terms of performance and interface, there is a trade-off. Applications requiring high starting torque and control over speed variations, despite the higher costs, may find Slip Ring Motors more cost-effective in the long run because alternative motor types might not meet their needs.

Squirrel Cage Motors:

  • Squirrel Cage Motors, by contrast, are simpler and cheaper to manufacture, which results in lower purchasing costs.
  • The significantly lower maintenance requirements underpin their cost-effectiveness across their lifecycle. Also, their robust design contributes to a longer lifespan, reducing the frequency of complete motor replacements and further enhancing their economic viability.
  • Their higher operational efficiency translates into energy cost savings over the lifetime of the motor, further strengthening its economic case.
  • Though their performance features might not be as versatile as Slip Ring Motors, for constant-speed applications they represent a cost-effective choice.

Within the grand context of our comparison, cost-effectiveness presents a culmination point, inviting users to evaluate both motors not only based on performance characteristics but also through a finance-centric lens. The comprehensive understanding we’ve built through this journey allows us to assess the implications of initial outlay, maintenance, energy efficiency, and expected service life, ensuring the motor chosen delivers the best balance of performance and cost-effectiveness for the application at hand.

Slip Ring Motors vs. Squirrel Cage Motors: Lifespan and Durability

The lifespan and durability of a motor generally correlate with its construct, maintenance parameters, and operational efficiency. With their unique designs, both Slip Ring Motors and Squirrel Cage Motors exhibit differing lifespans and degrees of durability.

Slip Ring Motors:

  • Slip Ring Motors, with their elaborate design incorporating brushes and slip rings, encounter more wear and tear due to the inevitable frictional losses and heat generation under operation. This could potentially shorten their lifespan compared to Squirrel Cage Motors.
  • However, with proper maintenance and timely replacement of brushes and slip rings, the service life of these motors can be considerably extended.
  • Their robust design allows them to endure harsh operating conditions, providing durability when used in suitable applications with sufficient maintenance provisions.

Squirrel Cage Motors:

  • Squirrel Cage Motors are renowned for their longevity, notably due to their simplified construct, low wear and tear, and reduced heat generation.
  • Their design eliminates the need for brushes and slip rings, reducing the chance of failures and extending the lifespan of the motors significantly.
  • They are known for their robustness under a wide range of operations, rendering high durability and making them a favorite for heavy-duty, continuous applications.

In sum, when we consider the comprehensive comparison of Slip Ring and Squirrel Cage Motors from the lifespan and durability perspective, the ability to understand each motor’s strengths and potential pitfalls grows. This analysis plays a vital role in selecting the right motor for any application, taking into account long-term reliability and performance over potentially many years of service.

Slip Ring Motors vs. Squirrel Cage Motors: Speed Control and Versatility

The level to which a motor can control speed and its operational versatility are crucial factors in applications that demand varying speed levels or adapting to different operational scenarios.

Slip Ring Motors:

  • Slip Ring Motors features a unique advantage in the arena of speed control. Their construction allows for inserting additional external resistance in the rotor circuit, which enables the control of rotor current and thereby the speed.
  • This feature presents a high level of operational versatility, making Slip Ring Motors suitable for applications that require variable speed and high starting torque, such as in driving lifts, cranes, and compressors.
  • However, this advantage comes with a trade-off of higher maintenance requirements and less energy efficiency, as discussed before.

Squirrel Cage Motors:

  • Squirrel Cage Motors, on the contrary, are typically designed for constant-speed applications. They offer less speed control compared to Slip Ring Motors due to their inherent design.
  • Nevertheless, their robust design and high-efficiency operation make these motors extremely versatile in their application. They are suitable for a wide range of constant-speed applications such as pumps, fans, blowers, conveyor systems, and many general machinery drives.
  • The speed control in these motors can be achieved but usually requires complex methods like variable frequency drives, which can add to the cost.

Understanding the speed control and versatility of both these motors offers valuable insights into their suitability in diverse scenarios. It helps in identifying the right motor for specific application environments, ensuring better alignment with performance requirements and subsequently, improved overall operational efficiency.

Slip Ring Motors vs. Squirrel Cage Motors: Starting Torque

Starting torque is an important factor affecting the performance of a motor. It is the force that the motor generates at the very beginning of its operation to overcome the inertia of the load. Both Slip Ring Motors and Squirrel Cage Motors have different properties when it comes to starting torque.

Slip Ring Motors:

  • Slip Ring Motors inherently have a high starting torque, courtesy of their wound rotor design. They produce a high torque per ampere of rotor current thanks to the additional external resistance inserted in the rotor circuit.
  • This high starting torque makes Slip Ring Motors particularly useful in applications that require a significant amount of torque to begin operation, such as lifting heavy loads or driving accelerators.
  • However, the stress exerted on the motor due to the high starting torque can lead to more wear and tear, requiring more frequent maintenance.

Squirrel Cage Motors:

  • Squirrel Cage Motors has a lower starting torque in comparison to Slip Ring Motors. Still, they are generally quite adequate for numerous constant-speed applications where the load requirement during startup is not exceptionally high.
  • In applications where higher starting torque is required, modifications can be made to the Squirrel Cage Motors, such as using a double cage design, but these options often come with additional costs.
  • Their lower starting torque leads to less stress on motor components during startup, reducing wear and tear, and extending their lifespan.

By understanding the starting torque of Slip Ring Motors and Squirrel Cage Motors, we gain vital insights into their capabilities under different load conditions. This knowledge aids in making effective motor selection decisions, aligning with specific operational needs, and promoting long-lasting and efficient performance.

Slip Ring Motors vs. Squirrel Cage Motors: Power Factor

The power factor, which is a measure of how effectively incoming power is used in the motor, holds its own significance when it comes to operational efficiency and energy consumption. Both Slip Ring Motors and Squirrel Cage Motors have distinct characteristics in terms of power factor.

Slip Ring Motors:

  • Slip Ring Motors typically have a lower power factor as compared to Squirrel Cage Motors. This is because of the phase shift between rotor and stator currents which produces a lower real power output for the same power input.
  • A low power factor can lead to higher energy consumption, which might increase operating costs in the long run.
  • However, the power factor of Slip Ring Motors can be improved to an extent by adding external resistance in the rotor circuit but this often comes with added complexity and costs.

Squirrel Cage Motors:

  • Squirrel Cage Motors generally have a higher power factor, close to unity under normal operating conditions, due to their simplified design and inherent operational characteristics.
  • A higher power factor results in more efficient usage of incoming power and leads to lower energy consumption, making these motors generally more cost-effective in terms of energy usage.
  • This higher power factor further reinforces the versatility of Squirrel Cage Motors, making them an ideal choice for most constant-speed applications where energy efficiency is a priority.

Understanding the nuances of the power factor provided by Slip Ring and Squirrel Cage Motors gives a deeper knowledge into their operational effectiveness. Remembering that a higher power factor equates to higher energy efficiency, the user can align the right choice of motor to the energy requirements of the specific application, promoting better operational efficiency and cost savings over time.

Slip Ring Motors vs. Squirrel Cage Motors: Application Suitability

The ability of a motor to function effectively in a particular environment or cater to specific load dynamics is what stipulates its suitability. Both Slip Ring Motors and Squirrel Cage Motors have specific application environments where they perform best.

Slip Ring Motors:

  • With their high starting torque and adjustable speed, Slip Ring Motors are particularly suitable for applications requiring high torque at startup or variable speed during operation. They are commonly used in elevators, hoists, cranes, compressors, and other heavy-load machinery environments.
  • Their strong performance in demanding conditions makes them an ideal choice for heavy-duty industries such as marine drives, mining, and industries that impose large mechanical stresses on electrical equipment.
  • However, their maintenance requirement, decreased energy efficiency, and lower power factor should be considered when assessing their suitability for any given application.

Squirrel Cage Motors:

  • Due to their robustness, low maintenance, high efficiency, and high power factor, Squirrel Cage Motors are best suited to applications requiring continuous operation at constant speed. They are extensively used in pumps, fans, conveyors, general machinery, heating ventilation, and air conditioning systems.
  • Their widespread application across several industries, such as manufacturing, construction, HVAC, and many others is a testimonial to their versatility.
  • Where high starting torque is not a critical requirement and emphasis is on reliability and energy efficiency, Squirrel Cage Motors often emerges as the most suitable choice.

By evaluating the application suitability of both types of motors, users are empowered to make well-informed decisions about which motor best suits their specific application environment. This ensures an alignment between expected performance and actual output, while also optimizing the longevity and cost-efficiency of the motor’s operation.

Slip Ring Motors vs. Squirrel Cage Motors: Environmental Considerations

The quest for greener technologies and reduced impact on the environment has elevated the importance of evaluating the environmental friendliness of a motor. Keeping this vital aspect in mind, let’s examine the environmental impact of both Slip Ring Motors and Squirrel Cage Motors.

Slip Ring Motors:

  • Slip Ring Motors have a lower power factor, which translates to reduced power efficiency, leading to higher energy consumption. This results in a higher environmental impact when considering energy usage and its carbon footprint.
  • Their higher maintenance requirement means more frequent replacement of parts like slip rings, brushes, and other components, which could potentially contribute to increased waste and resource consumption.
  • However, the ability to control speed according to the application’s requirements and the high starting torque can lead to better process optimization, potentially reducing overall environmental impact in some targeted applications.

Squirrel Cage Motors:

  • Squirrel Cage Motors features high power factors, leading to higher energy efficiency and reduced energy consumption, thus making them more environmentally friendly in terms of their carbon footprint.
  • Their reliability, low maintenance needs, and extended lifespan mean lesser material waste and fewer part replacements, reducing overall resource utilization and waste generation.
  • While they are primarily built for constant speed applications, incorporating methods like variable frequency drives can enable versatile motor speed control, further helping in conserving energy and minimizing environmental impact.

By understanding the environmental impact posed by Slip Ring Motors and Squirrel Cage Motors, users can make responsible decisions concerning the application of these motors in different scenarios. Such decisions, when taken collectively, contribute to the growing culture of environmental sustainability while balancing performance requirements.


Both Slip Ring Motors and Squirrel Cage Motors have their unique strengths and sets of applications. The choice between the two largely hinges on specific application needs and requirements. Understanding the intricacies of these motors aids in making well-informed decisions that yield better operational outcomes and more cost-efficient solutions. Whether you are looking for high starting torque or efficiency, this comparison should provide a helpful guide in your journey of engineering and innovation.