A traction motor is an electric motor that powers the wheels of a vehicle, converting electrical energy into the rotational force needed to move. You’ll find them in electric cars, trains, buses, and industrial equipment like forklifts. What sets a traction motor apart from other electric motors is its ability to deliver high torque at low speeds (critical for getting a heavy vehicle moving from a standstill) and to reverse its function during braking, acting as a generator that converts the vehicle’s momentum back into electrical energy.
How a Traction Motor Works
Every electric motor works on the same basic principle: electricity flowing through a coil creates a magnetic field, and the interaction between magnetic fields produces rotation. In a traction motor, this rotation is transferred to the wheels either through a gearbox or, in some designs, directly.
The key performance characteristic is the relationship between torque and speed. At low speeds, a traction motor produces its highest torque, which is why electric trains and cars accelerate so smoothly from a stop. As speed increases, torque decreases. Peak power output happens roughly in the middle of this range, at about half the motor’s maximum speed and half its maximum torque. This natural torque curve is actually ideal for vehicles, which need the most pulling force when starting and less as they reach cruising speed.
During braking, the motor reverses roles. Instead of consuming electricity to spin the wheels, the spinning wheels drive the motor, which now generates electricity that flows back into the battery or power system. This is called regenerative braking, and it’s one of the biggest efficiency advantages of electric propulsion. A locomotive traction motor, for example, seamlessly switches between consuming and producing energy hundreds of times per trip.
Types of Traction Motors
Several motor technologies compete in the traction space, each with distinct tradeoffs.
Permanent Magnet Motors
These use powerful magnets (typically containing rare earth elements like neodymium) built into the rotor. They offer the highest power density, meaning they pack more power into a smaller, lighter package than other designs. System efficiency is also higher across a wide load range, from 40% load all the way past 120% of rated capacity. Most modern EVs use some version of this technology. The downside is dependence on rare earth materials, which are expensive and concentrated in a few countries.
AC Induction Motors
Instead of permanent magnets, induction motors generate their magnetic field by inducing current in the rotor through electromagnetic interaction. They’re simpler, more rugged, and avoid rare earth materials entirely. Tesla has been the primary large-scale user of induction motors in EVs. The tradeoff is lower efficiency at partial loads and reduced power density compared to permanent magnet designs. At higher speeds, a phenomenon called back-EMF becomes more pronounced, which works to slow the motor and limits high-speed performance without sophisticated electronic control.
Wound Rotor Synchronous Motors
These replace permanent magnets with electrically energized coils in the rotor, eliminating rare earth materials while retaining good efficiency. BMW, Nissan, Renault, and Volkswagen are expected to be major users of this design, and suppliers like Schaeffler and BorgWarner have developed production versions. Demand for rare-earth-free motors is projected to grow at about 15% annually through 2037, making this the fastest-growing category.
Switched Reluctance Motors
The simplest design of all, with no magnets and no rotor windings. Honda’s venture arm has invested in a Canadian startup, Enedym, specializing in this technology. Historically these motors have suffered from noise and vibration issues, but advances in electronic control are making them viable for vehicles.
Traction Motors in Trains and Locomotives
Rail was the first major application for traction motors, and it remains one of the most demanding. A typical diesel-electric locomotive like the widely used EMD SD40-2 carries six traction motors, each rated at 536 kilowatts. The diesel engine produces about 3,100 horsepower, which drives an alternator that converts it to electricity at roughly 1,000 volts DC. That electricity feeds the six motors, each drawing up to 1,050 amps continuously. The locomotive maintains constant power output up to about 61 miles per hour, at which point the voltage limit of the system (around 1,300 volts) is reached.
Fully electric trains take power from overhead wires or a third rail and feed it directly to their traction motors, skipping the diesel engine and alternator entirely. This makes them significantly more efficient. Modern high-speed trains use AC traction motors controlled by variable-frequency drives that precisely manage speed and torque.
Traction Motors in Electric Vehicles
In a passenger EV, the traction motor replaces the internal combustion engine as the sole source of propulsion. Most EVs use a single motor driving one axle, or two motors for all-wheel drive. Some performance vehicles use three or even four motors.
There are two basic layouts. The most common is a centrally mounted motor connected to the wheels through a reduction gear and half-shafts, similar to how a conventional drivetrain works. The alternative is an in-wheel (hub) motor, where a motor sits inside each wheel hub. Hub motors eliminate the need for a transmission and driveshaft, freeing up interior space and allowing independent torque control at each wheel. However, they add unsprung weight to the wheels, which can hurt ride quality and handling. They also complicate tire changes and brake service. Most major automakers have stuck with centrally mounted motors for now.
Cooling and Thermal Management
Traction motors generate substantial heat, especially during hard acceleration or sustained hill climbing. How that heat is managed directly affects how much power the motor can sustain before it has to throttle back to protect itself.
Most EVs use indirect liquid cooling, where coolant circulates through channels in a jacket surrounding the motor. This is effective but can create uneven temperature distribution, with hot spots forming in areas farthest from the cooling channels. Some newer designs use oil immersion cooling, where the motor’s internal components are bathed directly in a thermally conductive, electrically insulating fluid (typically transformer oil). This provides more uniform cooling and can also handle heating the motor in cold weather. Air cooling is simpler and lighter but limited to lower-power applications like e-bikes and small industrial vehicles.
The Shift Away From Rare Earth Materials
The biggest material challenge facing traction motor manufacturing is the dependence on rare earth elements. Permanent magnet motors deliver the best performance, but the neodymium and dysprosium they require are expensive, environmentally costly to mine, and largely sourced from China.
The industry is actively pursuing alternatives. Stellantis partnered with U.S. startup Niron Magnetics in late 2025 to develop motors using “clean earth magnets” made from iron nitride, containing no rare earth elements at all. General Motors and Volkswagen are expected to incorporate induction motors (which need no magnets) into their EV lineups by 2030. The wound rotor synchronous motor has emerged as the most commercially ready alternative, with multiple European and Japanese automakers adopting it. Renault had been co-developing a rare-earth-free motor with supplier Valeo but ended that partnership, pivoting to sourcing certain components from China while manufacturing the rest internally, with full deployment targeted for 2028.
These shifts reflect a broader industry calculation: slightly lower peak efficiency is an acceptable tradeoff for supply chain security and lower material costs, especially as battery and power electronics improvements compensate for the difference.