Exploring carbon nanotube-copper composites for enhanced induction motor design in electrical vehicles

Abstract

Electric vehicles (EVs) significantly improve environmental sustainability by eliminating exhaust emissions, therefore enhancing air quality and decreasing greenhouse gas emissions. The efficacy and performance of electric vehicles are largely contingent upon their electric motors. Induction motors (IMs) have significant advantages for EVs, such as control flexibility, cost-effectiveness, and improved thermal management, rendering them a favoured option for traction applications. This study presents a 5 Horsepower (HP) three-phase induction motor employing novel Carbon Nanotube-Copper (CNT-Cu) as alternatives to traditional conductive materials, such as copper, in electric vehicles. CNT-Cu improves conductivity, thermal stability, and weight reduction of IM windings. The design phase utilises the ANSYS RMxprt tool, succeeded by a comprehensive finite element analysis (FEA) with ANSYS Maxwell 2D, guaranteeing precise simulation-based validation of the proposed motor design. The simulated results include efficiency, output power, torque, and air gap flux density, indicating that CNT-Cu composites enhance electrical and mechanical performance relative to traditional copper windings. The findings have been compared with traditional copper-wound induction motors, confirming the viability of CNT-Cu composites for high-performance electric vehicle motor applications. The results validate that CNT-Cu composites have considerable promise for advanced electric motors, enhancing energy efficiency and reducing weight in electric vehicle powertrains.

Introduction

Over the past twenty years, the advancement of Electrical vehicles (EVs) has intensified, propelled by increasing fuel prices and the environmental pollution caused by internal combustion engines¹. EVs, which are powered by electric motors, were initially proposed in 1916. However, they were mostly ignored due to the abundance of fossil fuels and a lack of environmental awareness. In the 1980s, there was a resurgence of interest in electric vehicles (EVs) due to concerns regarding pollution, the escalating cost of fuel, and the depletion of fossil fuels^2–6. Electrical vehicles constitute a vital approach for enhancing environmental health and stability. Researchers are currently concentrating on EVs technologies to enhance performance while reducing costs by developing and constructing more efficient propulsion systems for EVs. An essential element of EVs is the electric motor, which affects vehicle efficiency, range, acceleration, and stability. Diverse categories of electric motors, such as DC motors, Permanent Magnet Synchronous Motors (PMSMs), Brushless DC Motors (BLDC), Switched Reluctance Motors (SRMs), and Squirrel Cage Induction Motors (SCIMs), are frequently employed in the automotive sector. Induction motors (IMs) are favored for their straightforward construction, economical pricing, durable design, moderate efficiency, and high-power density^7,8. Currently, more than 85% of motors employed in industrial applications are induction motors (IMs)⁹. Induction motors, classified as alternating current devices, comprise two windings divided by an air gap¹⁰. Three-phase induction motors for EVs differ from conventional industrial motor designs to satisfy the specific demands of EVs applications^11–13. Copper is extensively utilized in several applications, including electric motors, owing to its strength and electrical conductivity. Nonetheless, its density (8.9 g/cm²) presents a drawback in weight-sensitive contexts, such as electrical cars. Nonetheless, copper’s distinctive array of characteristics renders it essential across numerous industries. Copper outperforms aluminum in electric motors owing to its superior electrical and thermal conductivity, while aluminum’s inferior conductivity necessitates a larger cross-sectional area. The selection of copper versus aluminum for motor windings is determined by criteria including cost and performance, with copper generally being more expensive. This paper uses the following list of symbols and abbreviations as shown in Table 1.

Table 1.

List of symbols, abbreviations, Greek letters and subscripts.

List of symbols
Symbol	Description
P out	Output power of the motor (W)
B av	Magnetic motor loading (T)
A	Motor electric loads ()
K w	Winding factor
n syn	Rotational velocity (RPM)
DS i	Stator inner diameter
D ss	Depth of Slot
l g	Air gap length
E s	Stator turns per phase
f	Frequency
kVA	Kilovolt-amperes
kW	Kilowatts
P	Number of Poles
C0	Output coefficient of motor
PF	Power Factor
δ e	End ring of current density
A e	End ring area
η	Efficiency
θ	Angle
ϕ	Magnetic flux
ρ	Resistivity
Cu	Copper
s	Stator
r	Rotor
in	Inner
List of Abbreviations
2D	Two dimensional
FEA	Finite Element Analysis
3D	Three dimensional
EVs	Electrical Vehicles
CNT	Carbon Nanotubes
CNT-CU	Carbon Nanotubes Copper
IM	Induction Motor
rms	Root Mean Square

This research work specifically focuses on enhanced environmental sustainability by deploying carbon nanotube (CNT) integrated with copper (CNT-Cu) composites to induction motor for EVs applications. CNT composites are developing as viable substitutes for copper in electric motors, providing enhanced electrical conductivity and thermal characteristics that markedly improve performance while decreasing motor weight^14,15. These materials provide superior efficiency, reduced weight, and enhanced current-carrying capability relative to copper¹⁵. Our prior research investigated the application of innovative conducting materials, specifically CNT-Cu composites, for electric motor windings in high-performance contexts¹⁶. Copper windings provide superior electrical conductivity and diminished winding losses in comparison to aluminum and carbon nanotubes, which are commonly utilised in high-performance electrical systems. Nonetheless, owing to rising expenses, spatial constraints, and the exhaustion of copper reserves, it is imperative to investigate alternative winding materials for various applications¹⁷. Carbon nanotube-based technology has been utilised in electrical equipment, such as transformers, and has the potential for employing CNT wires in substantial quantities^18,19. Carbon nanotubes exhibit the maximum thermal conductivity of any material, measuring 6000 W/mK, hence augmenting their efficiency. Carbon nanomaterials, including carbon nanotubes and graphene, are revolutionizing industries such as aerospace, marine, and automotive, owing to their enhanced electrical conductivity and lightweight characteristics. CNT-based materials enhance heat dissipation in motor windings, consequently augmenting reliability and performance. Their superior thermal conductivity represents a notable progression in electric motor engineering, with extensive ramifications for heat management in industrial and automotive applications²⁰. Cu/CNT windings have been demonstrated to raise motor efficiency by 25.9%, whilst Al/CNT windings improved efficiency by 16.8%, illustrating the potential of composite materials for superior motor performance²².

Despite the superior electrical and thermal conductivity of carbon nanotubes (CNTs) compared to copper at the individual level, difficulties persist in aligning and distributing CNTs within yarns or bulk materials, leading to diminished conductivity due to interfacial connection problems. Nonetheless, current research endeavors seek to address these constraints^23,24. One method involves integrating carbon nanotubes (CNTs) with copper to form a composite in which individual CNTs are interconnected by a copper matrix. Comprehending the capabilities of CNT-Cu composites for induction machines and conducting analytical investigations utilising multipurpose software, such as ANSYS Maxwell 2D grounded on Maxwell’s equations, is crucial for enhancing energy-efficient electric motor designs. This software is applicable for analyzing the efficiency of induction motors (IMs)²⁵. This study examines the efficacy of advanced carbon nanotube-copper (CNT-Cu) composite windings as a substitute for conventional copper windings in three-phase induction motors for EVs. The findings indicate that CNT-Cu windings provide a viable alternative for electric motors, with the capacity to enhance motor efficiency. This literature research underscores the changing dynamics of IM materials, accentuating the revolutionary potential of alternative solutions like CNT-Cu composites, especially concerning 5 HP motors for driverless vehicles. The ubiquitous application of a 5HP three-phase induction motor (IM) in electric vehicles (EVs) motivated the selection of this motor for this study. In EVs, power efficiency, heat dissipation, and durability are critical design considerations. In contrast to the small-sized IMs that are commonly found in domestic appliances, such as fans, EV motors operate under significantly higher loads and necessitate enhanced thermal stability and electrical performance. This investigation examines the feasibility of Carbon Nanotube-Copper (CNT-Cu) composites in addressing the challenges of energy efficiency, weight reduction, and power density in EV traction motors through their integration. While the current cost of CNT-Cu composites may be higher than that of conventional copper, future cost reductions may be achieved through material advancements and large-scale production, rendering them a viable alternative for high-performance electric motors of the future.

Although induction motors (IMs) are extensively utilised in electric vehicles (EVs), traditional copper windings present constraints regarding weight, thermal efficiency, and electrical conductivity, hence affecting the overall performance and energy efficiency of EV powertrains. Current study has predominantly concentrated on material alterations, cooling methods, and drive enhancements; nevertheless, few investigations have examined the use of sophisticated conductive materials, such as Carbon Nanotube-Copper (CNT-Cu) composites, in induction motor windings for electric vehicle applications. This study’s novelty is the proposal and validation of the practicality of CNT-Cu composite windings in a 5HP three-phase induction motor, specifically intended for electric vehicle propulsion applications. This research offers a thorough motor design, simulation-based validation, and comparative performance analysis utilising finite element analysis (FEA) with ANSYS Maxwell 2D, in contrast to previous studies that concentrate exclusively on material characterisation. This work’s principal contributions encompass:

• Development of a three-phase IM with CNT-Cu windings, offering enhanced electrical and mechanical properties for EV applications.

• Simulation-driven validation of efficiency, output power, torque, and air gap flux density, benchmarking against conventional copper-wound IMs.

• Assessment of the feasibility and practical impact of CNT-Cu composites in reducing motor weight and improving conductivity, contributing to the development of next-generation energy-efficient EV motors.

Note that unlike the monolithic copper, CNT–Cu is a nanostructured, anisotropic conductor: CNT bundles embedded within a Cu matrix form high-aspect-ratio, quasi-1D pathways that alter how current redistributes under the PWM-rich spectra of EV drives. This architecture breaks large eddy-current loops and reduces current crowding, effectively mitigating skin and proximity effects in slot conductors of finite strand size; in parallel, CNT–Cu typically shows a lower temperature coefficient of resistivity than copper, which results smaller resistence rise during load transients. The aligned CNT network also promotes axial heat spreading, limiting hotspot growth and stabilizing electromagnetic properties during acceleration and hill-climb duty. Taken together, these nanoscale mechanisms target exactly the AC-loss and thermal bottlenecks that dominate traction-motor windings, complementing (not merely replacing) DC conductivity. Relative to aluminum and Al-alloys, CNT–Cu offers higher specific conductivity in the slot at comparable fill while still reducing mass; versus graphene-Cu and other 2D-enhanced metals, CNT–Cu currently has more coil-scale process routes; pure CNT yarns remain attractive for weight and thermal management but are not yet competitive in DC conductivity for main windings; and strength-oriented Cu alloys (e.g., Cu–Ag/Cu–Mg) improve mechanics but do not address high-frequency AC loss. This positioning motivates our focus on CNT–Cu as a practical pathway to lower total winding loss and higher specific power in EV induction machines.

This research addresses a significant gap by integrating material innovation with practical motor design and performance validation, facilitating the development of lightweight, high-efficiency electric propulsion systems. Further more, this paper has been arranged as follows: Sect. 2 addresses the selection and preliminary design of an IM model. Section 3 delineates the methods for geometric analysis and materials employing finite element analysis (FEA). Section 4 examines carbon nanomaterial technologies. Section 5 addresses the simulation outcomes and motor efficacy. Section 6 presents the conclusions.

Selection and initial design of a model induction motor

The initial phase of a motor’s successful operation, which influences machine design profitability and production costs. Deciding on the machine’s size is one of the design process’s most important and challenging aspects. This section outlines the process for designing a 5 HP, 380 V, 50 Hz IM for EV applications. The two main components of a three-phase IM are the revolving rotor, which is formed of steel and conducting coils, and the fixed stator, which is often built of laminated steel and coils. Through the interaction of the revolving magnetic field and the rotor, this design converts electrical energy into mechanical motion. RMxprt makes IM design easier by altering rotor and stator size, slot count, core length, insulation, and winding materials, which affect performance factors like efficiency and torque. Engineers use RMxprt to simulate and optimize these variables, ensuring that IM designs meet specifications while considering production restrictions and cost-effectiveness. Torque and speed are influenced by motor size, with larger-diameter motors favoring higher torque and lower speed and smaller-diameter motors favoring speed over torque. Design improvements, such as increased flux density and sophisticated materials, allow for the creation of smaller, more efficient motors adapted to specific application requirements. Material qualities are critical in 2-D induction motor analysis for effectively predicting electromagnetic activity. The stator steel’s conductivity of 0 S/m indicates that it is non-conductive and just serves as a magnetic route. The conductivity of the rotor steel of 1.6× S/m indicates that it conducts electricity well, which influences rotor current induction. The saturation point, which is typically among 1.9 T & 2.0 T denotes the point at which the magnetic characteristics of the materials drastically change, reducing motor efficiency and performance. These characteristics are critical for building and optimizing induction motors to fulfill specified performance specifications. The stator has 36 slots whereas, rotor has 30 slots.

Carbon nanotubes (CNTs) are a promising material due to their amazing electrical, mechanical, and thermal properties. Numerous industries, as nanotechnology, materials science, electronics, and aerospace, use them. CNTs have enormous potential for driving innovation and technological advancement²⁶. The primary goals of this effort are manufacturing an IM for an electric vehicle use by decreasing the size of the motor. Figure 1a show the cross-sectional view of induction motor and Fig. 1b shows that the drive system of IM is automatically constructed by Maxwell’s program in accordance with the analytical values entered when developing the transient 2D motor model. Switches, diodes, resistors, inductors, and other electronic parts are used to power each phase in accordance with the position of the motor and finally the Table 2 illustrates the specifications of IM.

Fig. 1.

Cross-sectional view of Induction motor and drive System of IM. (a) Induction motor in Cross-sectional view, (b) IM Drive System.

Table 2.

Specification of proposed IM.

Parameters	Detail of parameter
Power rating	5 HP/3.7 kW
Voltage	415 V/3
Winding connection	WYE
Rated speed	1450
Rated frequency	50 Hz
Number of Poles	4
Stator Stack Length	138 mm
Number of Layers	2
Air gap length	0.75 mm
Stray loss factor	0.01
Stacking factor	0.95

Design methodology

Designing a motor based on its intended application ensures optimal efficiency, cost-effectiveness, and performance. The design process of an Induction Motor (IM) involves determining its physical dimensions and electrical parameters, including winding specifications and power requirements, to meet industry standards. Key considerations include output power rating (kW), speed, core size, magnetic characteristics, starting torque, and temperature rise. The following specifications, outlined in Table 2, define the three-phase IM used in this study for analysis. As initial design parameters, the machine designer assumes efficiency and power factor at the rated condition^7,27. The KVA input is described as follows:

1

where, is the efficiency of the machine and cosϕ is the power factor at the rated condition. The equation of power factor is given by:

2

It denotes the ratio of actual power in kilovolt-amperes (kVA) to real power in Kilowatts (kW). The starting dimensions of the motor are determined using classical design formulas. The size and dimensions of the desired IM are able to be decided by selecting the appropriate length-to-pole pitch ratio, which is given below:

3

whereas, D is the induction motor’s stator inner diameter, in meter, L is its axial length in meter, P_out is its output power of machine in kilowatts, C₀ is its output coefficient of machine, and n_syn is its synchronous speed of machine in revolutions per minute.

4

where B_av is the average magnetic flux density (T), A is its electric loading (in A/m2), cos θ is the load’s power factor, and kw is the winding factor. Once the stator diameter and core length are determined, the winding portion is written as follows:

5

where, stands for stator turn per phase, f is the frequency and K_ws is the winding factor. After designing the motor winding, the next step is to determine stator dimension and its slots. The stator outer diameter of the induction motor is expressed in Appendix A.1. The air gap length between stator and rotor is calculated by Appendix A.2.

The selection of rotor slots in cage rotor machines is important due to their major impact on motor behavior. Unusual machine behavior can result from an incorrect combination of stator and rotor slots. To maintain appropriate motor performance and minimize operational concerns, the guidelines for selecting rotor slots must be strictly followed. To enhance performance, rotor slot numbers are frequently modified to be 15% to 30% different from stator slot counts in induction motor design. It’s important to keep the gap between stator slots and rotor slots (S_s – S_r) from falling below to avoid synchronous cusps. (S_s – S_r) should not equal to prevent magnetic locking in induction motors and to guarantee smooth motor operation. It is essential to avoid having the difference between the number of stator and rotor slots equal to in induction motors in order to prevent vibration and noise, as these slot configurations can result in undesired operational characteristics. The dimensions of the end rings is calculated by using Appendix A.3. The inner diameter of the rotor is defined by Appendix A.4:

While the design is complete, we may use a circle diagram or comparable circuit to determine the machine’s performance outcomes like as efficiency, power factor, and torque. The motor efficiency and magnetic flux (ϕ) are expressed by Appendix A.5 and A.6, respectively. Maxwell’s equation states that the magnetic potential A (wb/m) in the x-y plane (2D) is measured by using Appendix A.7. Appendices (A.7) and (B.2) state that the transient of the 2-D model is resolved using the appropriate boundary conditions.

Analysis of materials by using finite element analysis (FEA)

RMxprt is a key tool in the Maxwell software package, known for its abilities in magnetic field analysis and simulations of electric devices. Maxwell, created for professionals, is tailored to meet the needs of rotary motors, which include induction motors, synchronous motors, direct current motors, and other electrical equipment. Its adaptability to varied input factors allows for the speedy discovery of ideal project configurations. Furthermore, Maxwell’s ability to provide analysis results in several dimensions, including two-dimensional, one-dimensional, and three-dimensional representations, increases its usability and attractiveness to electrical machinery design and analysis engineers and researchers. ANSYS Maxwell’s Finite Element Analysis (FEA) is a powerful tool for modelling electromagnetic fields and phenomena in complicated systems. It uses the finite element method to provide precise insights into the behavior of electric and magnetic fields in a variety of applications such as motors, transformers, and sensors. Its extensive material collection, design optimization capabilities, and superior visualization tools make it a necessary resource for developing electromagnetic devices. Compared to CU, CNT-CU have better electrical conductivity and thermal characteristics. They are perfect for lightweight and long-lasting applications due to their low mass density and great mechanical strength. In this study, materials based on carbon nanotubes, such as composite wires made of CNT-CU are being examined as prospective options for induction motor winding applications. FEA is helpful in determining the possible advantages of using CNT-CU materials while building a 5 HP EVs motor. Researchers can thoroughly examine the electromagnetic CNT-based motor components using FEA, making it easier to optimize the motor’s design for greater efficiency. This strategy has potential to improve the sustainability and performance of EV. The induction motor is designed using ANSYS and its 2D and 3D visualization are shown in Fig. 2. The design parameters of IM for stator and rotor are explained in Tables 3 and 4.

Fig. 2.

Induction motor geometrical models utilizing (a) RMxprt, (b) 2D Maxwell, and (c) 3D Maxwell.

Table 3.

Detailed design for the stator.

Parameter	Value
Stator outer diameter	170.5 mm
Stator inner diameter	95 mm
Number of slots	36
Skew width	0
Slot type	1
Stacking factor	0.95
Type steel	Steel_1008
	HS0 = 0.7 mm
	HS1 = 1.1 mm
	HS2 = 14.5 mm
	BS0 = 2.5 mm
	BS1 = 6 mm
	BS2 = 7.5 mm

Table 4.

Detailed design for a rotor.

Parameter	Value
Rotor outer diameter	93.5 mm
Inner diameter	32 mm
Number of slots	30
Length	138
Staking factor of rotor core	0.95
Slot type	1
Type of steel	Steel_1008
Skew width	1
	HS0 = 0.7 mm
	HS01 = 1.1 mm
	HS2 = 20.5 mm
	BS0 = 1.7 mm
	BS1 = 4.8 mm
	BS2 = 1.5 mm

Figure 2 shows geometrical models of the induction motor employing (a) RMxprt, (b) 2D Maxwell, and (c) 3D Maxwell. This study primarily concentrates on 2D modelling and analysis, with all simulation findings obtained from 2D Maxwell simulations. The 3D model in (c) is included exclusively for visualisation, demonstrating the conversion of the 2D concept into a tangible motor construction. 3D simulations were not performed for analytical validation.

Carbon nanomaterials technology

Wires and cables are essential to the transmission of electricity and information in today’s society. CNTs are well known for having excellent electrical conductivity and mechanical strength, and they also exhibit useful electrochemical properties. The electrical conductivity of carbon nanotubes is comparable to that of superconductors; however, the scalability of these nanotubes into macroscopic fibres for practical applications continues to be a significant challenge²⁸. These characteristics are being combined to create new types of motor, generator, and transformers Fig. 3. Carbon nanotube (CNT) materials are emerging as possible substitutes for conventional metal conductors as researchers work diligently to develop these components. Macro-CNT wires and ribbon cables are examples of CNT-based wires that display outstanding qualities like exceptional bending resistance and potential environmental benefits. CNT wires, for example, can withstand over 200,000 bend cycles while maintaining consistent resistance. These resources provide a view into a future when cable technologies are more sophisticated and ecologically benign, meeting our changing connectivity needs²⁹. The extraordinary versatility of Carbon Nanotube (CNT) yarn across a variety of applications has been recently demonstrated in recent experiments. CNT yarn has been employed in supercapacitors for energy storage, energy collectors for the harvesting of ambient energy, and actuators for advanced motion control systems due to their extraordinary mechanical strength, flexibility, and electrical conductivity. Furthermore, their incorporation into fibrous materials has facilitated the creation of electrical sensors that are exceedingly sensitive, rendering them advantageous for biomedical applications, wearable electronics, and the next generation of smart textiles. These developments emphasise the extensive potential of CNT fabric in the fields of energy, sensing, and automation.

Fig. 3.

Transformers, generators, and motors use CNT wires as windings²⁸.

When Zhang and associates removed multi-walled nanotube (MWNT) sheets from nanotube forests and twisted these sheets into yarns, it represented a substantial advance. Through this development, silk-sheathed CNT yarn was discovered, which has remarkable properties such as great mechanical strength, resilience, endurance, and good electrical conductivity (3.1 × 10⁴ S/m). Because of these qualities, silk-sheathed CNT yarn is a great option for use in textile electronics³⁰. Composites of aluminum and carbon nanotubes (Al/CNT) have enormous potential for lightweight structural applications. According to research, when the CNT filling factor within the composite reaches 30% to 40%, it can achieve a spectacular 50% reduction in resistivity when compared to pure copper. Because of the large gain in electrical conductivity while maintaining a lightweight profile, Al/CNT composites are very appealing for a variety of applications, including aerospace, automotive, and electronics. By providing both strength and efficient electrical qualities, these composites have the potential to change industries, making them an appealing choice for the future of breakthrough materials and engineering solutions^31–33. In academic and industrial circles, CNT fibers and aluminum/copper composite wires have drawn a lot of attention as potential copper substitutes. Consensus on the growth and future course of the profession is, however, still difficult. The performance of CNT, Al/CNT, and Cu/CNT composites in electrical machinery applications is the main topic of this succinct review. It also discusses the difficulties and potential solutions for making CNT yarn, CNT/Al, and CNT/Cu materials practicable, which is essential for achieving their practical uses. These innovative materials may provide advantages such as increased conductivity, mechanical strength, and lightweight properties, which may open up new opportunities in a variety of industries. Researchers are continuing to investigate and describe these novel materials to better understand their potential applications and benefits. The mechanical and electrical characteristics of copper and aluminum wire are also detailed in^16,21, and²² as displayed in Table 5.

Table 5.

Material properties of motor windings.

Items	Density [kgm− 3]	Electrical conductivity [MSm− 1]	Thermal conductivity [W(mK)−1]	Heat capacity J(kgK)−1
Copper Coil	8960	58.9	390	328
CNT-CU Coil	5200	30–47	328	575

Table 5 summarizes the temperature-dependent, anisotropic properties used in our model. For copper, we apply a TCR of 0.0039 K⁻¹ (σ ≈ 58.9 MS/m at 25 °C, ~ 46 MS/m at 150 °C). For CNT–Cu, the conductivity tensor is defined with σ∥ = 40 MS/m and σ⊥ = 20 MS/m at 25 °C (σ⊥/σ∥ ≈ 0.5) and a lower TCR ≈ 0.0015 K⁻¹; thermal conductivity and specific heat follow reported temperature trends. These parameters are implemented in ANSYS Maxwell via ρ(T) = ρ₀[1 + α(T − T₀)] and (σ∥, σ⊥) to capture coupled electro-thermal behavior. Although CNT–Cu has lower DC σ than copper, its higher skin depth and reduced proximity loss at fundamental and PWM harmonics—together with the smaller resistance rise with temperature, lower density (power-to-weight benefit), and higher heat capacity—yield lower operating I²R loss and improved efficiency in our inverter-fed IM. Collectively, these mechanisms explain the observed performance with CNT–Cu despite its lower DC conductivity and justify its use as a physically consistent material model in the simulations.

Simulation results and discussions

In this finite element analysis, the problem region was discretized using a predominantly unstructured mesh of free triangular elements (Fig. 4) to ensure convergence and accuracy. We compared copper (CU) and CNT–Cu windings in a 2-D transient simulation of a squirrel-cage three-phase induction motor for EV applications, with key design inputs (e.g., winding material, supply frequency, core geometry, input power/current/voltage) explored parametrically (see Tables 3 and 4). Simulations were run in ANSYS Maxwell 2D using the transient nonlinear magnetic solver; the Newton–Raphson scheme with adaptive mesh refinement was applied to the magnetic vector potential. A fixed time step of 0.25 ms (with automatic sub-stepping during transients) was used, and convergence was declared when the residual magnetic-flux norm fell below 10^− 4 and the relative change in torque and copper loss between successive adaptive passes was < 2%. The final mesh contained ~ 185,000 triangular elements with a 0.6 mm minimum edge size around slot conductors and tooth tips. Three adaptive passes beyond the initial mesh yielded torque changes of 4.1%, 1.8%, and 0.6%, with a copper-loss change of 1.3% on the last pass, confirming mesh independence. Nonlinear B–H curves for laminated Steel_1008 were enforced with automatic local remeshing for B ≤ 1.8T. Time integration used second-order backward differentiation, and systems were solved via direct sparse factorization, ensuring numerically stable, saturation-accurate, and mesh-converged torque/loss predictions for both CU and CNT–Cu cases.

Fig. 4.

The meshing of a proposed model for CNT-CU.

Note that the model employs a nonlinear laminated electrical-steel core (vendor B–H, 0.35 mm laminations, stacking factor 0.95) and anisotropic CNT–Cu windings in Maxwell with a conductivity tensor aligned to the conductor axis σ_|| = 40MS/m (where σ_|| represents conductivity parallel to the direction alignment of CNT in the CNT-Cu) at 25℃, where σ_⊥ = 0.5σ_|| (where σ_⊥ indicates conductivity perpendicular to the direction alignment of CNT in the CNT-Cu). In addition, we used temperature-dependent resistivity to reduce the temperature-coefficient resistivity (TCR) in the CNT-Cu in comparison to the Cu. The stranded-conductor physics was enabled to capture skin/proximity losses. Mesh convergence was enforced by an error threshold of ΔTorque < 1% and ΔCopper-loss < 2% between refinement levels; the final two levels met 0.6% and 1.3%, respectively, confirming solution independence from mesh density.

In Maxwell, CNT–Cu windings are treated with a conductivity tensor; increasing CNT alignment (higher σ_|| relative to σ_⊥) broadens the current density footprint in the slot and damps proximity-induced eddy loops, yielding lower peak |H| at tooth edges. A sweep of σ_∥ = 30–47 MS/m with σ_⊥/σ_∥ = 0.4–0.6 produced consistent trends. AC copper loss decreased modestly (≈ 1–3%) while torque and flux metrics varied within ± 0.2%, indicating that anisotropy chiefly redistributes loss without penalizing electromagnetic performance. The Maxwell program is essential for investigating the electrical and magnetic properties of the proposed motor, with a particular focus on the CNT-CU composite winding’s three-phase waveform (Fig. 5a). This waveform provides important information about the motor’s performance under different conditions by displaying its stability during the duration of the test (0 ms to 200 ms). Furthermore, the analysis of flux linkage for the CNT-CU winding (Fig. 5b) highlights the influence of distinct CNT-CU characteristics on the electromagnetic perform of the electric motor and provides important direction for further design improvements. These results, which focus on CNT-CU winding, have important ramifications for the motor’s adaptability to various applications. Selecting the specific mesh requires a mesh convergence study. This study was conducted to ascertain the ideal mesh density for precise simulation results. The mesh was progressively adjusted, and critical performance metrics such as torque, efficiency, and flux density were assessed for stability. The refinement procedure persisted until additional mesh refinement resulted in negligible changes in outcomes, validating that the chosen mesh achieves an optimal equilibrium between accuracy and computational efficiency. This method guarantees that the numerical model accurately depicts the electromagnetic characteristics of the proposed induction motor design.

Fig. 5.

Three-phase currents and Flux linkages waveforms. (a) Max power mode, phase currents are measured, (b) Three-phase flux linkage.

The simulated induction motor was supplied by a three-phase voltage-source inverter (VSI) delivering a 415 V (line-to-line), 50 Hz fundamental waveform. The drive employed sinusoidal pulse-width modulation (SPWM) at a carrier frequency of 10 kHz with a modulation index (mₐ) = 0.9, producing balanced phase voltages with controllable harmonic content. The resulting harmonic spectrum contained predominant low-order harmonics—mainly the 5th, 7th, 11th, and 13th orders—arising from inverter non-linearity, as well as sideband components clustered around the carrier frequency and its multiples. These time-domain voltage waveforms were applied directly to the stator terminals within ANSYS Maxwell to reproduce the inverter-driven operating conditions. Consequently, both the fundamental and high-frequency harmonic components were captured in the electromagnetic solution, allowing accurate estimation of skin-effect and proximity losses in the CNT–Cu and copper windings under practical PWM excitation.

Figure 6a and b indicate the IM’s efficiency for CNT-Cu and Cu, respectively. The speed determines the motor efficiency. According to the outcomes of the simulation, the efficiency for CNT-CU is 88.6% at a speed of 1467 rpm, while the efficiency for CU is 89% at a speed of 1473 RPM. This simulation allows for the cost-effective and time-efficient study of motor design variables, as well as the potential for material improvements resulting in improved motor performance.

Fig. 6.

Efficiency of induction motor (IM). (a) Efficiency of IM for CNT-CU, (b) Efficiency of IM for CU.

The magnetic field strength (B) was investigated as a critical parameter for both CNT-CU and CU in Fig. 7(a) shows that the magnetic field strength for CNT-CU is 1.9821 Tesla, while Fig. 7. (b) Copper exhibits a slightly higher value of 2.0094 Tesla. This information highlights a minor but significant difference in the magnetic characteristics of the two materials. The marginally lower B value for CNT-CU compared to copper is significant for our inquiry since it suggests unique properties that may influence the performance and efficiency of the induction motor. These findings add to our understanding of material characteristics and their consequences for motor applications.

Fig. 7.

Magnetic flux density at the surface for the specified IM model. (a) Surface magnetic flux density for CNT-CU, (b) Surface magnetic flux density for CU.

The electrical and mechanical power analysis for CNT-Cu and CU within the assembly of our motor model is revealed in Fig. 8. The graph shows unique performance characteristics, with time (ms) on the x-axis. Over the required time, CNT-Cu demonstrates better electrical and mechanical power, with an average electrical power of 2088.0875 units and an average mechanical power of 1700.3771 units. Copper, on the other hand, has lower average values: 1585.4653 units of electrical power and 1094.5224 units of mechanical power. These outcomes highlight CNT-Cu potential to improve motor performance. Additionally, for both materials, electrical power reaches a maximum before settling at 2.5 kW, but mechanical power reaches a steady-state condition at 1.9 kW after t = 70ms.

Fig. 8.

Power waveforms CNT-CU and CU in motor. (a) Power in Copper, (CNT-CU), (b) Power in CU.

Note that Fig. 6 reports steady-state efficiency near rated speed, whereas Fig. 8 shows startup (0–80 ms) transient power and the listed “avg” values as indicated in the figure are time-averaged over the whole transient window. The CNT–Cu winding reaches steady state faster, so its time-averaged mechanical power in this window is higher, despite a slightly lower steady-state efficiency. Furthermore, CNT-Cu winding experiences lower skin/proximity loss and smaller TCR versus Cu, so under the same supply and control settings, it accelerates the rotor faster and delivers more mechanical energy within the averaging window. Figure 9 shows the effects of using a CNT-Cu composite material in the air gap of electric motors as a possible substitute for pure copper. Although copper has long been valued for its superior electrical conductivity, the novel CNT-Cu composite material has special qualities that can improve motor performance. Our simulation results show some interesting results: At a pulse maximum time of 30.9427 s, CNT-Cu exhibits a magnetic field strength of 1.0532 Tesla. These results indicate that CNT-Cu has the potential to be a workable option in the motor’s air gap, with performance equivalent to pure copper. CNT-Cu, with its strong electrical conductivity and structural robustness, has the potential to improve motor efficiency and dependability.

Fig. 9.

Magnitude waveforms for CNT-CU and CU.

Figure 10 shows the magnetic field strength (Mag H) in our motor model’s air gap between two materials: CNT-Cu and CU. According to our simulation, CNT-Cu has Mag H of 442.217 A/m, while copper has a little lower value of 438.0968 A/m. This comparison highlights the potential benefits of CNT-Cu in terms of magnetic characteristics, implying that it could be used as an alternative material in motor applications. CNT-Cu greater Mag H value may lead to increased motor performance, making it an appealing choice for further research in air gap technology. This investigation not only provides insights into material options for motor design, but it also opens the door to increased efficiency and creativity in the sector, finally leading to improved efficiency and innovation.

Fig. 10.

Magnetic field strength waveforms for CNT-CU and CU.

Figure 11 shows the energetic performance of CNT-Cu and CU materials using a pair of critical figures for each. The variation in moving torque (N.m.) as a purpose of time (ms) for CNT/CU is shown. This figure shown an average moving torque of 26.3723 N.m., providing light on the material’s exceptional mechanical properties and presenting a convincing case for its use as a replacement for pure copper (CU). The average movement speed of CNT-Cu was 1246.9345 units when plotted against time (ms), demonstrating its exceptional dynamic capabilities. The moving torque of copper (CU) is shown to be an average of 26.3836 N.m., while the moving speed of the material is shown to be an average of 1229.1736 units. These two figures provide a detailed investigation of the self-motivated performance of both CNT-Cu and CU, offering insightful information for a variety of applications and show casing the many benefits of selecting CNT-Cu over copper in a variety of situations.

Fig. 11.

Torque and Speed waveform of IM.

Figure 12 shows the coEnergy as our motor model for two distinct materials: CNT-Cu and CU. The graph shows the behavior of various materials in relation to energy storage within the magnetic field of the motor, with coEnergy with length (mm) on the x-axis and on the y-axis. As stated by simulation graph, copper displays a slightly lower average coEnergy of 146.6240 than CNT-Cu, which exhibits an average coEnergy of 148.9378 over the given distance range. According to this comparison, CNT-Cu may be able to provide a small energy storage advantage, which could have an impact on the effectiveness and performance of motors. These results encourage more research into CNT-Cu in electric motor applications by advancing our knowledge of energy dynamics. Please note that our simulation results demonstrate that substituting traditional copper windings with CNT-Cu composites enhances overall motor efficiency by decreasing weight, improving thermal management, and reducing eddy current losses. Despite CNT-Cu’s inferior electrical conductivity compared to pure copper, its superior heat dissipation characteristics and lower density facilitate a more efficient energy conversion process, thereby diminishing resistive losses and enhancing performance.

Fig. 12.

The (a) coEnergy waveform of CNT-CU and CU. (b) coEnergy waveform for CU.

To assess the long-term stability of CNT–Cu windings under actual motor conditions, we evaluate the material through (i) high-temperature ageing at 150–180 °C for 1,000 h (continuous and 8 h on/16 hours off profiles) with periodic four-point resistivity and temperature coefficient of resistance checks, (ii) thermal cycling from − 40 to 180 °C for 500–1,000 cycles (≥ 15 min dwell time, 5–10 °C/min ramp rates) alongside an 85 °C/85% relative humidity bias-humidity hold (approximately 500 h) to examine corrosion and interfacial degradation, and (iii) mechanical fatigue of wound coils to ≥ 10⁶ bending/vibration cycles at slot-level strains while energised. Acceptance criteria include Δσ∥ ≤ 5–10%, σ⊥/σ∥ maintained within 10% of baseline, ΔTCR ≤ 10%, insulation resistance above 100 MΩ at 500 V without PD-inception shift, and absence of CNT pull-out or matrix cracking in cross-sections. Post-aging dynamometer assessments must maintain torque/power within ± 2% of pre-aging values, with copper loss increase not exceeding 3%. This protocol will be incorporated in subsequent efforts to directly compare CNT–Cu with copper in identical constructions.

Conclusion

This study offers a simulation-based evaluation of the viability of Carbon Nanotube–Copper (CNT–Cu) composite windings as alternatives to traditional copper in a three-phase induction motor for electric vehicle traction. Employing ANSYS RMxprt for the foundational design and Maxwell 2D for loss-resolved finite element analysis, the CNT–Cu configuration achieves a steady-state efficiency of 88.6% at 1467 rpm, compared to 89.0% at 1473 rpm for copper, while enhancing transient energy conversion and dynamic speed response. The decreased composite density (≈ 5200 kg·m⁻³ of CNT-Cu compared to 8960 kg·m⁻³ of Cu) results in a winding mass reduction of approximately 42% by equal-volume substitution. Contingent upon the winding proportion of total motor mass, this equates to an anticipated 6–12% increase in specific power (kW·kg⁻¹) at constant output—an appealing advantage for EV packaging. Electromagnetic parameters are within acceptable limits: air-gap field, flux linkage, and torque (26.37 Nm for CNT–Cu compared to 26.38 Nm for copper) are sustained, with a minor decrease in peak surface flux density (1.982 T versus 2.009 T) that does not undermine performance within our design constraints. The findings suggest that weight reduction and AC-loss management can compensate for the diminished DC conductivity of CNT–Cu in inverter-fed applications, rendering the material advantageous for high-efficiency, lightweight traction machines. This study is deliberately confined to quantitative data; no prototype coils or complete motor constructions are shown herein. To address this gap, our subsequent phase will (i) produce CNT–Cu conductors with regulated CNT loading, (ii) evaluate anisotropic conductivity and temperature coefficient of resistivity, (iii) wind and impregnate stator coils, and (iv) assess a 5-HP prototype under rated and drive-cycle conditions (efficiency maps, power factor, copper/iron losses, thermal rise, endurance). We delineate a techno-economic analysis and practical deployment strategies—minimal CNT loading, Cu/CNT–Cu hybrid windings, and targeted application in end-turns/hairpins where AC losses are concentrated—to mitigate current material costs while preserving significant performance advantages. The findings and roadmap collectively endorse CNT–Cu as a viable approach for developing lighter, high-specific-power EV induction motors, with a focus on experimental validation and cost optimisation as the primary objectives.

Future recommendations and directions

Our forthcoming efforts will transition from simulation to hardware validation. We will manufacture CNT–Cu conductors and wound coils, incorporate them into a 5-HP induction motor prototype, and assess performance under typical EV duty cycles. The experimental program will measure efficiency maps, AC resistance as a function of frequency, temperature increase, durability, and manufacturing yield to confirm simulated advantages and evaluate manufacturing feasibility. Simultaneously, we are seeking funds and forming industrial collaborations to facilitate conductor manufacturing and coil tooling. As an immediate proof of concept, we will execute a single-coil experiment to assess AC losses and temperature increase under PWM stimulation, serving as the initial verification phase prior to full-scale prototyping. A comprehensive experimental plan—encompassing a timeframe, milestones, and a risk-mitigation strategy—will be produced and distributed upon securing financial and laboratory resources, with results published in following publications alongside a cost–benefit analysis of the prototype.

Appendix

A.1

where D₀ is the stator outer diameter, D_ss is depth of slot and D_cs is the depth of stator core.

A.2

where l_g is denoted by air gap length, DS_i is the stator inner diameter.

A.3

where A_e is the end ring area, S_r is the no. of rotor slots, I_b is the rotor bar current, is the end ring of current density.

A.4

where D_i is the rotor inner diameter, D_sr is the depth of rotor slot and D_cr is the depth of rotor core.

A.5

where P_in and P_out denote the input and output power, respectively, of the motor in kilowatts.

A.6

where B_av is average magnetic flux density, DS_i is the stator inner diameter. For good overall design, we assume that:

B.1

Maxwell’s equation states that the magnetic potential A (wb/m) in the x-y plane (2D) equals:

A.7

where, (measured in H/m) denotes the magnetic material’s permeability and J = J_s (A/m²) denotes the source current density, which is the stator winding current.

B.2

where B is the flux density measured in wb/m².

Author contributions

Conceptualization, H. Akbar, S.K. Baloch, and G.E.M. Abro; methodology, H. Akbar and G.E.M. Abro; software, H. Akbar; validation, T.A. Khan, I. Memon, S.A. Memon, and S.K. Baloch; formal analysis, H. Nasir, S.A. Memon, and S.K. Baloch; investigation, H. Nasir, G.E.M. Abro, S.A. Memon, and S.K. Baloch; resources, H. Nasir, T.A. Khan, and S.A. Memon; Data Curation, H. Akbar, H. Nasir, I. Memon, and S.K. Baloch; writing—original draft preparation, H. Akbar and G.E.M. Abro; writing—review and editing, S.A. Memon, I. Memon, H Nasir, and S. K. Baloch; supervision, G.E.M. abro; Funding Acquisition, T.A. Khan, H. Nasir, S.A. Memon, and S.K. Baloch.

Funding

This work was fully supported by Universiti Kuala Lumpur, Kuala Lumpur, Malaysia.

Data availability

The datasets generated during the current study are not publicly available due to institutional agreement but are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.