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What Is A Stator? (What It Is, What It Does, FAQs)

October 15, 2021

What is a stator? 
If you own a bike, you might say it’s the same thing as the car’s alternator since it generates electrical power. 

In a sense, that’s true. 
However, the stator is actually only a piece of the mechanism behind this. 

So, what exactly does a stator do?

In this article, we’ll delve a little deeper to get to know this electromagnetic component. We’ll also cover some related FAQs to gain a better understanding of the stator. 

This Article Contains

Let’s get started.

What Is A Stator?

The stator is the stationary part of rotary electromagnetic devices like the alternator, electric motor, or generator. 

You might hear the term “stator” used interchangeably with “alternator” or “generator,” even though it only makes up a part of those larger devices. This is especially apparent when talking about the motorcycle alternator — which is more often called a stator. 

Its basic construction is an outer frame, core, and windings. 

The outer stator frame provides support for the stator core. The stator core is typically thin, steel laminations inserted with the stator winding, and the stator winding (or stator coil) is made of insulated copper wire. 

When an electrical current is applied, together, the stator core and stator winding become an electromagnet. 

Next, let’s see what this electromagnetic component does. 

What Does A Stator Do?

Energy flows through the stator to and from a rotating rotor. 

The stator is always stationary while the rotor spins, either within it or around it. 
In this way, the stator can act as the:

Here’s what a stator does in common machinery:

The stator isn’t limited to electromotive applications, though its structure may be a little different in other systems. In hydrodynamic systems (like a torque converter), the stator guides fluid flow to or from the rotating turbine rotor of the system.

And in some devices, the stator is a permanent magnet array instead of an electric coil. You may see this in certain types of car starter motors.

We’ve covered the basics of the stator. 
Now, let’s go through some stator FAQs.

Here are answers to some stator questions you may have in mind:

1. How Do The Stator And Rotor Work?

To get a basic understanding of how a stator and rotor work together in an electrical machine, let’s look at a typical induction motor:

A. How A Stator Works

The stator frame houses the stator core that’s wound with the stator coil. 

The stator coil winding is usually made of magnet wire (typically insulated aluminum or copper wire). An electromagnetic field is generated when an alternating current (AC) is applied to the coil winding. 

The alternating nature of the current changes the polarity of the stator poles in the magnetic field, making the magnetic field (not the stator) rotate. Depending on the coil winding setup, a stator can usually have 2, 4, or 6 stator poles.

B. How A Rotor Works

The rotor is the moving electrical component in a motor. 
Similar to the stator, the spinning rotor also has a rotor core and rotor winding. 

The most common electrical motor rotor construction type is called a squirrel cage due to its shape. 
In a squirrel cage rotor, the rotor core is a cylinder of steel laminations, with copper or aluminum conductors embedded in its surface (representing the rotor winding). 

When the stator’s moving magnetic field cuts across the rotor’s conductors, it induces a current. This current creates a magnetic field around the rotor conductors. As the magnetic field in the stator shifts poles, so does the magnetic field in the rotor — and it’s this interaction that spins the rotor. 

2. Is A Motorcycle Stator The Same As A Car Alternator?

Almost the same, but not quite. 
An automotive AC alternator is a self-contained, externally mounted component that creates a direct current (DC) output. It’s an all-in-one unit that generates a vehicle’s required power. 

The smaller motorcycle requires a simpler system than regular automotive alternators. A motorcycle “alternator” is more commonly called a “stator” and is accompanied by a regulator/rectifier. 

To generate AC power, the stator works with a rotor, known as the flywheel. The AC power is converted to DC through the rectifier, while the regulator regulates the voltage to the battery. 

The motorcycle stator is usually located inside the engine and is considered to be part of it. The regulator/rectifier is typically found elsewhere. The regulator/rectifier could be two separate pieces in older bikes, but more modern constructions have them compacted into one unit.

Before the stator (and alternator systems), a magneto was used on motorcycles. The magneto served the same function as the stator, including providing power to the engine spark plug, but had a more basic form.

3. What Can Cause Motorcycle Stator Failure?

Here are the two most common reasons for motorcycle stator failure:

A. Usage And Wear Over Time

Like any electrical component, the stator is subject to wear and tear. Exposure to vibration, environment and changing temperatures will have an impact on the stator’s lifespan. 

B. Voltage Overload

Voltage overload is another primary cause behind stator failure. 

This happens when too many electrical accessories run at the same time — like using the headlights, GPS, heated grips, and stereo simultaneously. The stator has to work harder to keep up with the power demand and eventually burns out.

4. What Is An AC Motor?

An AC motor converts alternating current into mechanical energy
In the AC motor, AC power comes from the magnetic fields generated through coil windings around an output shaft. 

There are generally two types of AC motors:

The AC motor can be a three-phase or single-phase configuration. 
Three-phase motors are typically used for industrial bulk power conversion, while you’ll often find single-phase AC motors in home and office use — like water heaters or garden equipment.

5. What Is A DC Motor?

The DC motor converts direct current to mechanical energy.
A DC motor typically comprises a stator, a rotor, an armature, and a commutator with brushes. 

In a DC motor, a magnet array functions as the stator, the armature is placed on the rotor, and a commutator flips the direct current flow from one coil to the other. 

There are two types of DC motors:

DC motors are powered by batteries or some other power source that generates constant voltage, and they offer better speed variation and control with more torque than AC motors. 

You’ll find them in a wide range of appliances, from electric razors to electric car windows.

Final Thoughts

The stator may have slightly different meanings, depending on whether it’s seen from a motorcycle owner’s point of view or a purely electric motor standing. A car owner may not be aware of it at all, as it’s simply a part of the better-known alternator. 

Regardless, it’s evident that the stator is crucial to the overall function of any electric motor. 
While it’s not an electrical component that fails easily, the next time your car alternator takes a dive, it could very well be an ailing stator. 

But don’t worry. 
For any car concerns, you can always rely on RepairSmith to help you out. 

RepairSmith is a mobile vehicle repair and maintenance solution, available 7-days a week. Online booking is hassle-free, all repairs and fixes are conducted with high-quality tools and parts, and come with a 12-month | 12,000-mile warranty

Just contact them, and their ASE-certified mechanics will be right in your driveway to lend you a hand!