Reacher Technology Co.,Ltd

Reacher Technology Co.,Ltd

Inrunner Vs Outrunner


Your brushless motor purchase is a very important decision to make. And brushless inrunner or brushless outrunner options could influence this decision.

The verdict might get extremely complicated for you.

Which motor would you pick between inrunner vs. outrunner?

In the outrunner, the magnets are stationed on the piston. And on the inrunner motor, it’s placed in the center. The outrunner motor is less efficient than the inrunner motor. Both of the motors have decent heat dissipation.

This won’t be satisfactory for you to differentiate between the two motors. Have a look at the thorough comparison we’ve illustrated in this writing.

Inrunner Vs. Outrunner: Basic Differences

Let’s have a glimpse of the basic differences between inrunner and outrunner motor

Features Inrunners Outrunners
RPM and Torque High RPM’s, Low torque Low RPM’s, high torque
Efficiency More efficient than outrunners Less efficient than inrunners
Heat Dissipation Better heat dissipation Heat dissipation is not bad
Size Smaller diameter, larger in length Larger diameter, smaller in length

Inrunner VS. Outrunner: Head To Head Contest

We realize only the fundamental contrasts will not be sufficient. Thus, partake in a straight-on contest between inrunner and outrunner.


In the outrunner, the magnets are stationed on the piston. And the piston whirls outwardly. Within the engine are the piston windings. They don’t twirl, they are secure on the spot.

On the inrunner engine, you essentially have the direct inverse. On the external side of the engine is the container. The container in this condition does not swirl and is fixed.

The piston windings are seated within the top of the container. When you swirl the motor shaft of an inrunner, you are swiveling the piston. It likewise incorporates super durable magnets similar to the outrunner. The thing that matters is that they are currently at the focal point of the engine.

Generally, this would be the more conventional sort of electric motor. Particularly in case, you know about huge AC motors or even old brushed DC motors.

Bulk Differences

Brushless outrunner motors will have a larger diameter vs an inrunner motor of similar weights. Also, outrunner motors are smaller in length. Contrariwise, Inrunners are compact in width and generally wider in height.

Manual size is one sector that your requisition that may be restricted. However, other trade-offs would have to be evaluated as we will get into below.

RPM / Volt (Kv)

You should correctly select the appropriate Kv motor. Something else, the danger of wearing a power module out is enormously expanded. In case the power system wears out, check your brushless motor with a multimeter.

An inrunner engine of comparable size to a brushless outrunner engine will have massive Kv. Though motors with unique and identical bulk and Kv alternatives give a fair reach. Outrunner motors will generally have a poorer Kv quality.

This is essential in your preference for a brushless motor to suit your requisition.

Torque Comparison

The larger momentum converts directly into more torque being created. Hence the outrunner motor will normally generate more torque vs an inrunner motor.

This relationship ties in with the fact that outrunners have a lower RPM/Volt. The association between Kv and torque is conversely relative. As RPM per volt (Kv) expands, the force of the engine diminishes.


This can be a tough comparison. Even the explanation has many reliances. These can be all you name it.

From the constructive size correlation with the nature of the engine. To the constructor of the engine, power generation of the engine, and several more.

For the most part, an inrunner engine is more systematic than an outrunner.

Waste Heat

How about we consider the temperature that an engine outputs. If your brushless motor overheats then it’s not a good brushless motor.

If we take a gander at the outrunner engine, heat squanders through its focal point. The origin of calefaction is obviously the stator windings of the engine.

The stator windings of the outrunner are situated at the center of the engine. The high temperature should move to the focal point of the engine being the engine shaft. Then it’s directed outward through the engine shaft.

An outrunner’s answer for heat is to have enormous available cooling vents. On the off chance that to permit air to stream over the windings straightforwardly

This immediate resource gives a magnificent surface. Furthermore, an extremely huge region for heat to move.

Air is a terrible conductor of high temperatures. By expanding the measure of a surface region, an inrunner can dispose of abundant heat energy.

Having the option to dispose of junk heat permits the inrunner to run cool. Furthermore, it’s more productive for comparable force generation on an engine of equivalent size/weight.

Final Verdict

The air gap surface of outrunner motors is substantially larger than inrunner motors. Nevertheless, this doesn’t recommend that you ought to favor outrunners over inrunner engines. Try to think about the speed and torque that you need in your motor.

Select carefully. You will rejoice in better performance of your motor!


Question: Are brushless outrunner motors waterproof?

Answer: The fact is brushless motors are sealed however they are not really damp-proof. Water is always adulterated in a pond or pool or downpour. That’s why it delivers small crumbs to the bearings in a brushless motor.

Question: What does a brushless machine do?

Answer: In construction, brushless engines are generally utilized for movement control. Brushless engines are preferably fitted for construction implementations. Given their power substance, great speed-force attributes, high productivity, and easy care.

Question: How long do brushless inrunner motors last?

Answer: Generally a brushless motor (inrunner or outrunner) has a long life expectancy. They can attain a huge number of hours normally. As there are no brushes.


Hope we’ve demonstrated everything to assess between inrunner vs. outrunner. You shouldn’t have any trouble now picking between these two.

Let us know which one you’ve decided to go with.

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