Every electric motor has a stationary part (the stator), a spinning part (the rotor), and a way to keep current switching so the rotor keeps turning. The rest of the electric motor parts hold those three together, keep them cool, or stop them from cooking themselves. Below we break down each part, show what typically fails, and explain when a repair beats a replacement.
What are the parts of an electric motor?
We tore down a cheap 130-size brushed DC motor, an N20 gear motor and a small brushless drone motor for this article. The names change a little between types, but the jobs stay the same.
| Part | What it does | Where you find it |
|---|---|---|
| Stator | Creates the fixed magnetic field | All motors |
| Rotor (armature in brushed DC) | Spins and turns the shaft | All motors |
| Windings | Copper coils that become electromagnets | Rotor in brushed DC, stator in BLDC and AC |
| Core | Laminated steel that concentrates the magnetic field | Inside rotor and stator |
| Commutator | Flips coil current every half turn | Brushed DC only |
| Brushes | Carbon contacts that feed the commutator | Brushed DC only |
| Shaft | Carries torque out of the motor | All motors |
| Bearings or bushings | Let the shaft spin with low friction | All motors |
| Housing, end bells, covers | Hold alignment, shield parts, mount the motor | All motors |
Stator and rotor
The stator is the outer shell’s magnetic side. In a 130 motor it is two curved ferrite magnets glued inside the steel can. In a brushless motor it is a ring of copper-wound teeth, and the magnets sit on the rotor instead.
The rotor is everything that spins. Its core is built from thin stacked steel sheets, each one insulated from the next. A solid lump of steel would let eddy currents swirl through it, wasting power as heat. That is why every motor core you open looks like a stack of thin plates.
Windings and insulation
Windings are enamelled copper “magnet wire.” The enamel is the only thing stopping turns from shorting to each other. Once it scorches, the motor loses torque, draws more current and runs hotter, so the damage speeds itself up.
Industrial motors are sold by insulation class, which tells us how hot the windings can safely run.
| Insulation class | Max winding temperature |
|---|---|
| A | 105 °C |
| B | 130 °C |
| F | 155 °C |
| H | 180 °C |
Premium industrial motors often use Class F insulation but are rated to run at Class B temperatures. That margin is a big reason they last decades.
Commutator and brushes
In a brushed DC motor, the commutator is a split copper ring on the shaft. Two carbon brushes press against it. As the rotor turns, the brushes touch different segments and reverse current in each coil at the right moment, so the rotor always chases the magnetic field ahead of it.
Brushless motors replace this with an electronic speed controller. Some use Hall sensors to read rotor position. Others sense it from the back-EMF on the windings.
Shaft, bearings and housing
The shaft is hardened steel. Hobby sizes are tiny: a 130 motor has a 2 mm shaft, and an N20 gear motor has a 3 mm D-shaped output shaft. Small cheap motors usually ride on sintered bronze bushings. Bigger ones use ball bearings, often the 608 size (8 mm bore, 22 mm outside, 7 mm wide) that also shows up in skateboards and 3D printers.
Housings are steel or aluminum. Aluminum sheds heat better and weighs less, which is why many brushless motors and modern industrial frames use it. The end bells hold the bearings in line, and the bases or mounting flanges bolt the whole thing down.
Cooling and thermal protection
Larger motors carry a fan on the shaft for cooling. A totally enclosed fan-cooled (TEFC) motor blows air across finned covers on the outside while keeping dust out of the inside.
Many AC motors also hide a thermal protector in the windings. Klixon is the best-known brand. It is a bimetal disc that snaps open when the windings overheat and closes again once they cool. If an appliance motor stops and restarts by itself after a few minutes, that protector is doing its job.
Explosion-proof motors take enclosure design further. Their housings are built to contain an internal spark or flame so it cannot ignite gas or dust outside. You will meet them in fuel and grain facilities, not on a robot chassis.
The “motor cell”: the simplest motor you can build
People searching for a motor cell are usually after the homopolar motor. It is one AA cell, a neodymium disc magnet stuck to its negative end, and a bent copper wire touching the positive tip and the magnet’s edge. The wire spins.
It has only three parts: a power source, a magnetic field and a conductor. That makes it a great way to understand what every larger motor is doing. It also shorts the cell, so the wire and battery get hot within seconds.
Power check
A homopolar motor is a dead short across the cell. Run it for a few seconds at a time, use alkaline cells only, and never try it with lithium cells.
Worked example: estimating stall current
Let’s say we measure 2.5 Ω across the terminals of a small brushed motor with a multimeter and plan to run it at 6 V. At stall the motor produces no back-EMF, so Ohm’s law gives 6 ÷ 2.5 = 2.4 A.
That number matters. A microcontroller’s general purpose input output pins supply milliamps, not amps. A motor must always go through a driver such as a DRV8833 or TB6612FNG. Most of our Arduino projects with wheels burn their first chip by skipping that step.
Maker tip
Rotate the shaft slowly while measuring winding resistance on a brushed motor. If one position reads open or wildly different, you have a broken coil or a dirty commutator segment.
What typically fails on an electric motor?
| Failure | Symptom | Usual fix |
|---|---|---|
| Worn bearings or bushings | Growling, wobble, heat at the ends | Replace bearings |
| Worn brushes | Sparking, stutter, dead spots | Replace brushes or the motor |
| Burned winding insulation | Burnt smell, high current, weak torque | Rewind or replace |
| Failed start capacitor (AC) | Hums but won’t start | Replace capacitor |
| Tripped or failed thermal protector | Stops, then restarts | Fix overload, replace protector |
| Broken lead or terminal | Intermittent or dead | Resolder the lead |
Bearings fail first in most industrial motors. In hobby motors it is brushes and commutators, especially when we push them past their rated voltage.
Finding replacement parts
For industrial and appliance motors, bearings, capacitors, fans, fan covers, brushes and thermal protectors are all sold as individual parts. Match the part number on the old one, and for bearings read the size printed on the shield.
For hobby motors under about $5, replacement parts barely exist. We accept that and swap the whole motor. The exceptions are suppression capacitors and leads, which a decent soldering iron sorts out in two minutes.
FAQ
What are the parts of the electric motor?
The stator, rotor, windings, laminated core, shaft, bearings and housing. Brushed DC motors add a commutator and brushes. Many AC motors add a fan, a capacitor and a thermal protector.
Can you repair an electric motor?
Yes. Bearings, brushes, capacitors, leads and fans are straightforward swaps. Burned windings need professional rewinding, which only pays off on larger, expensive motors.
What are the three main components of an electric motor?
The stator, the rotor, and the commutation system. Brushed motors switch current with a commutator and brushes, while brushless motors use an electronic controller.
What are the motor parts?
“Motor parts” usually means the replaceable items: bearings, brushes, capacitors, fans, covers, terminal boxes and thermal protectors. The core electrical parts, the stator and rotor, are rarely sold separately.
