What the heck is a brushless motor, and why are brushless power tools better than ones with brushed motors?
While brushless motors aren’t exactly a new technology, power tool brands have only recently begun to explore their full potential in power tools. Many brands are designing their brushless tools from the ground up, and adding in other premium features to deliver more for the step up in price.
Milwaukee’s M12 and M18 Fuel brushless tool lineups seem to be the fastest-growing, but other brands are starting to catch up with fantastic innovations of their own.
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Now, towards the end of 2014, there are brushless drills, impact drivers and wrenches, saws, rotary hammers, and oscillating tools. There’s even a brushless band saw, and another brand came out with a brushless framing nailer.
Related: Check out our latest brushless tool coverage
With new brushless tools coming out all the time, even by consumer brands such as Craftsman, you’re probably hearing brushless thrown around a lot in product descriptions and marketing, and wondering what it all means.
Here’s a quick primer into brushed motors, brushless motors, and why tools equipped with brushless motors are so darned good.
DC Brushed Motors
A basic brushed motor has an armature (rotor), commutator, brushes, axle and permanent magnets. Current is applied through the brushes, which are in physical and electrical contact with the commutator. Current then passes through the coiled armature, creating a magnetic field.
The created magnetic fields interact with those of the permanent magnets that surround the armature, causing the armature to rotate around the axle. If you apply greater current, such as when you squeeze the trigger of a cordless power tool harder, you will create stronger magnetic fields in the armature, resulting in greater interaction forces and thus faster rotation.
As you can see in the diagram, highlighted in red, the brushes are in contact with the commutator. Friction between the brushes and the commutator results in a slight drop in speed and thermal energy losses. In addition, the brushes may need to be replaced periodically as they wear out over time with use.
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DC Brushless Motors
In a brushless motor, there are no brushes, and thus no physical contact that could lead to frictional energy losses. Instead of the armature being located on the rotor with permanent magnets fixed to the surrounding shell (stator), permanent magnets are located on the brushless rotor with the armature’s electromagnetic coils in fixed positions surrounding it.
In a brushed motor, the commutator reverses the current flow through the armature coils, flipping the magnetic fields so that the rotor continues to spin. In a brushless motor, an electronic control switches the phase of current through the armature windings at precise timings to accomplish the rotational response.
Brushless vs. Brushed Motors
Brushless motors are more expensive to design and manufacture, but they are typically much more efficient than brushed motors. This leads to:
- less maintenance and longer life
- more power
- longer runtime
Often, brands have a choice in how they balance a tool’s power and runtime for optimal performance. Some might lean towards making a more powerful tool, others might lean towards making one that’s longer lasting before a battery swap or recharge is needed.
Brushless motors have become powerful enough to where brands boast about their premium brushless cordless tools having “corded-like performance.”
And, combined with latest generation high capacity Li-ion battery packs (we’re now at 5.0Ah), brushless tools provide better than ever cordless runtime as well.
Brushless Cordless Power Tools
When this post was first published in early 2012, Dewalt and Milwaukee were the first two mainstream brands to come out with brushless power tools. We predicted that other brands would follow the trend, and that brushless motors would be incorporated into other tools beyond drills and drivers.
Now, there seems to be no limit as to the types of tools that can be redesigned with brushless motors. Also, as mentioned earlier, power tool brands occasionally build other premium features into their brushless tools.
For example, Milwaukee’s M12 Fuel brushless drill has a 1/2″ chuck instead of 3/8″. Many brands’ brushless impact drivers and wrenches now offer electronic speed and torque settings that allow you to dial down the power depending on the application and fastener size.
With all the benefits of brushless power tools, it’s no wonder why they top brushless tools in many areas.
In our best cordless drills, best impact drivers, and best cordless oscillating tools recommendations, brushless tools earned highest honors.
There is a downside to brushless cordless tools – they’re pricey. They’re more expensive to design and manufacture, and so they cost more to end users. The bright side is that brands often design brushless tools with premium features and improved capabilities to help you see past the higher pricing. Kits are often bundled with the latest-and-greatest Li-ion battery packs to make them even more compelling.
Additional Considerations
A brushless vs. brushed motor comparison is not exactly as black and white as described. For example, moving the armature from the rotor to the stator also results in a decrease in mass and radial mass distribution of the rotor. In other words, the rotor of a brushless motor often has a much lower moment of inertia than that of a brushed motor. This means that a brushed motor rotor is more resistant to rotation. (Visualize a spinning ice skater with their arms reaching out vs. at their sides.)
So it’s not just about boosting efficiency by reducing brush-commutator frictional energy losses. Additional fundamental advantages of brushless motors include improved heat dissipation, flatter torque, reduced electrical noise, and greater power output.
This post was originally published on February 8, 2012, and republished with updated information on October 30th, 2014.
jeff_williams
Thanks for the primer. Any benefit to getting this technology onto corded tools? Besides no brushes to replace, maybe less amperage and heat, is there anything else to offset the higher cost? Are brushless motors smaller in size?
Stuart
I believe that there’s much less of a benefit to update corded tools with brushless motors. Plus, the tech changes since corded tools often feature AC motors, not DC. With corded tools, the goal is usually raw power, and runtime is rarely a concern since the tool is powered from a seemingly infinite source.
Brushless motors may sometimes be smaller in size, but I’m not certain. In the case of the new Dewalt brushless impact driver, they achieved a higher max-torque rating (1500 in-lbs vs 1400), and greater runtime in what looks to be a same-size form factor. The decrease in overall tool length may be attributed to both the brushless motor and new chuck designs.
If they designed the motor to be a little smaller, the runtime improvement would be less significant and the max torque would drop. We will probably see smaller brushless motors used in 12V tools in the future, if costs drop and brand managers can justify the R&D. I would say that that’s the direction things are headed since there’s a ceiling as to how much smaller, lighter, and more powerful these 12V tools can be made to be.
The comparison of brushless vs brushed is not quite the same as lithium-ion vs Ni-Cad battery packs. Li-ion is more energy-dense, meaning you can produce physically smaller packs with comparable or even improved performance. In this case, the efficiency is greatly improved, resulting in less current draw to achieve the same power.
If you bump up the current draw, you don’t see as much of a difference in runtime as you do in speed and power. It will be interesting to see which path different manufacturers choose. Different designs mean that some brands will seek a runtime advantage and others will seek the title for best-in-class power.
Ken
The D26456 corded sander from Dewalt has a brushless motor:
http://www.dewalt.com/tools/woodworking-sanders-random-orbital-sanders-d26456.aspx
As well as the Porter Cable version : https://toolguyd.com/porter-cable-low-profile-5-inch-random-orbital-sander/
Stuart
Thanks for the info! I didn’t even think about sanders when considering brushless motors in corded tools. With these types of tools, torque is not exactly a concern, but the advantages in size and lower maintenance is definitely noted. It also makes sense that continuous-run corded tools might benefit most from brushless motors.
greg e
grate read!
Fred
Typically small DC fans, specifically for PC’s & electronics, have been running brushless motors for decades. Not a lot of torque needed to push less than 100CFM of warm air, so brushless are chosen for other criteria; specifically they don’t make as much noise and run well continuously, allowing different bearings (single & double ball are much more common than sleeve in these applications) which can also change the performance of the final result.
Another issue is efficiency; if it were a big benefit years ago to introduce brushless across all cordless tool motors, it would have been done. Likely now either battery tech has slowed down in improvements per $ of research, or the efficiency of the motor design has taken a leap forward in economy, specifically economy of scale.
Finally, think of the fact that there is no solid contact between brushes & stator, something that dust (in the PC fans) or sand/sawdust (in your corded sander) will not dramatically decrease the life of the tool like a brushed motor would. One of the biggest things that leads to shortened life for brushed motors is physical deformation, typically from some particulate damage rather than electrical (like switch burn) and the fact that brushes are often brittle materials that chip when they deform, instead of bend or flex in a more predictable manner.
Stuart
Good points there, thank you for your insight!
With brushless fans, you do need more sophisticated electronic controls than with a brushed fan. My feeling is that the additional costs associated with have been largely minimized as a side effect as manufacturers implement more complex circuitry to optimize the performance of li-ion batteries.
I agree with you that it seems like brushless motors were the next step now that the advantages of li-ion batteries have been fully exploited. At this point, moving forward required a technological jump, with brushless motors being perfectly fitting.
Yes, some manufacturers have already released brushless tools, but they haven’t realized the tech’s full potential yet. And if they have, they definitely need to turn their attention to their marketing departments. Hitachi’s got quite a few brushless tools on the market, but you hardly seem them at jobsites.
Fred @ One Project Closer
Fred, first off, great name. Second, really insightful comment… I’m curious as to what types of PC fans this applies to. I ask because my first job (when I was 14) was in IT tech repair. I worked for a really low budget IT shop in a conveyor manufacturing company. We used to repair those fans all the time because the computers that sat out in our shop were subjected to so much gunk. Our usual solution was to pry open the cap on the fan, dump some oil in it, spin it ’til it ran again, and then probably do the same thing again 90 days later.
Fred
Most PC fans manufactured starting in the mid 90’s for the high end started introducing brushless fans gradually. By about 2003 or so, nearly every fan 80mm or larger was about 50% likely to be brushless, and by about 2006 it was almost entirely brushless across the board. They made up with simplicity in assembly what they paid in increased complexity in design. To the manufacturer, a sale of 10k fans was fine, they were sold and when the buyer wanted replacements they would choose to come back or not. They didn’t care much about longevity.
Prior to roughly 96 though, there were say 100 manufacturers of DC motors (of this size) in Asia instead of maybe 20 or so after say 2001. Now it mattered that you wanted repeat business because your scale was increasing exponentially, as one company bought another or one factory shut down or changed focus. This is when they started to really focus on bearings. Your fans worked when you re-oiled them because as the sleeves wore down and became thinner, they needed more oil mass to fill the same volume and not rub the motor. You essentially created ‘floating’ bearings (with a different fluid and geometry for the solid, you would have what they now call Fluid Dynamic Bearings – very high end stuff that works similar to your over-oiled fluid sleeves).
Now PC fans, especially the higher end ones will have double ball or hydrostatic, fluid dynamic, combination ball/sleeve, even evaporative closed systems for lubrication. This is what really leads to the longevity or downfall of a fan-sized motor. The motor itself will probably not burn out if there is no undue force applied to it; as bearings wear, the motor works harder and either burns out that way, or by the bearings deteriorate and either parts of the bearings themselves, or the particles they help to keep out, touching parts of the motors to cause shorts.
We used to make fun of the ‘double balls bearing’ cheap chinese fans when I worked at a PC store, but think that nowadays, even on a $40k turbocharged car, it’s more likely than not they used sleeves for the turbo itself. Different tech leaps forward in different industries; when I was in college, one of my roommates knew as much about turbos and engines as I knew about computers, and I was shocked when I found out that (comparing the norm in the PC industry was double ball bearings for fans) unless you go after the very very expensive ones, you will get sleeve bearings with almost any turbo assembly.
Scott
One thing to consider also with PCs is that they are very sensitive to RFI (EMI). Brushed motors cause a lot of RFI noise in comparison to brushless motors. Floppy drives used a flat brushless design while earlier similar type drives (early 5.25″ and 8″ floppies) used a brushed type. As far as I know, all motors in modern computers (personal, servers, super, etc) use only brushless types of motors for any part that uses an electric motor.
Jerry
I do farm maintenance, often in harsh conditions, and my experiences with brushless motors are far better than the brush type. Tool use in abrasive dust eats up not only brushes, but the contacts on the motor as well (I think it is called the commutator or maybe armature). Once this area gets ‘burnt’, even new brushes don’t make the tool work properly again. You can sometimes spin the armature in a drill press, and use Emory cloth to try to refresh the contacts, but it is usually only a short term fix, and usually a replacement tool will soon need to be purchased, as most of the time repairs are more than the used tool is worth. Brushless tools don’t have this problem, but power surges can harm the electronics in a corded tool. Cordless should not have this problem, as well as being safer in possible flammable environments such as grain dust. If cost competitive, I believe this will be the next big thing.
Stuart
Those are great points, thanks! The new Dewalt and Milwaukee brushless tools still look to have venting, though, so they’re not completely sealed. Still, it does look like there are fewer and narrower openings than before. And yes, no brushes will probably mean less sparking, although I would probably still be hesitant to use such a drill or driver in a flammable or explosive environment.
Phil
I can see a fair amount of efficiency and power gained through the use of brushless motors such as this. Brushed motors are actually a bit of a compromise in the way the switching occurs. Because of the inherent nature of a brush and commutator, there are inevitable moments where two or more armature windings are shorted together. This causes power loss through eddy current braking and reduced efficiency. In the case where a motor is bidirectional (reversible drills, etc) a compromise has to be made in the angle of the commutator/brushes so the motor performs equally in forward and reverse. If the motor is meant to turn in only one direction, the switching angle can be optimized for that direction. Even many of the cordless drills have their motors optimized in the forward direction a bit. If you run the drill unloaded at full power in the forward direction and then do the same in reverse, often you will hear the motor running slightly slower in reverse. Since the majority of the drill/driver usage is in the forward direction, that’s where the power is optimized. In the case of brushless motors, the switching angle can be optimized in both directions, and since the switching is done electronically, there is no overlap causing momentary shorted windings either. Both of these increase efficiency considerably.
Since the permanent magnet(s) are on the rotor, they can be made smaller, and are more likely to be the very powerful neodymium type. Since a brushless motor depends on the controlling circuitry knowing the position of the rotor at all times, the same controller can be used as an effective electronic brake. The usual electric brake setups for brushed motors simply shorts the terminals of the free spinning motor and relying on the back current to bring the motor to a stop. This works pretty well, but it is very hard on the brushes. Watch the short blast of sparks when you release the trigger on the typical drill or driver as it comes to a stop. This lessens brush life considerably.
I love all my cordless tools, but the one problem I find with the ones I use in metalworking is the permanent magnets collect metal chips and dust. I will take the tools apart and use high pressure air as well as sticky tape and tweezers to try and clean the motors of this debris. Even though a brushless motor still has a strong set of magnets, they are spinning at a high speed and less likely to pick up magnetic debris. The cooling fans found in the motors will help clear some of the flung debris. Universal motors (on corded AC tools) and the stator windings of brushless motors are operating under alternating currents and tend to shed debris. It is possible to make a sealed brushless motor since the heat generated by the coils can be dissipated through the stator frame, but they probably use the fans to cool the electronics as well.
Stuart
Thanks, Phil, for sharing your insight! I can’t say that I’ve ever had to clear ferrous chips from the insides of my cordless tools, but I can definitely see how that could happen. Your other points are as straightforward and helpful.
Phil
Stuart: Just don’t make the mistake I made a while back when I had finished drilling and shaping a mounting bracket I had made, brushed all the chips and filings into one spot while cleaning up, then accidentally knocking a cordless drill I was using right smack into the middle of the pile. 😉
After that happened, the drill would not turn freely since the vent slots on the one side were completely filled with metal chips. Some of this got into the motor itself and wedged into the magnets and against the armature. I put the drill on the side until I could open it up, remove the motor and used a high pressure (non-safety, don’t tell anyone) blow gun to work the chips out of the motor. It took a while, since the motor was a sealed assembly, but I got it all cleaned up. The frameless motors found on the more recent compact tools are actually easier to clean, since opening up the housing exposes the individual motor parts (brushes, armature, field magnets) and these can be taken out individually to clear messes.
This is not a big deal if the tools aren’t used around a lot of metalworking and ferrous debris. Wood, concrete and nonferrous dust blows right out of the tools without issue, just aim an air nozzle into the slots and blow away.
Joshua
All the brushed DC motors I’ve seen have more than two windings, meaning they’re not shorted together. Otherwise you’d have a dead spot
Fred @ One Project Closer
Stuart, Killer article. Nice primer for me. I generally knew what the term meant, but the diagrams are helpful. I want to say that last time I talked to the TTI rep (TTI owns Milwaukee, Ridgid and Ryobi–at least for the purposes of cordless power) he said that Ridgid was on its way with this technology. Right now I’ve got a DeWALT 20v max and a Ridgid 18V in the shop (along with like 8 others). I think the 20v max is still a brush motor. Anyhow, of the two its a really tough call which one I like better. The DeWALT is lighter, for sure, but I like the grip feel on the Ridgid just a little better. Need to work with them more to pass judgment.
Stuart
Thanks! I figured that questions were bound to come up and that it’s best to inform folks before “brushless” becomes a full-fledged dazzling buzzword.
The newest Ridgid 18V drills do have some killer ergonomics as well, but in a drill vs. drill comparison. I prefer the Dewalt 20V Max a tad bit better. Talking about looks, I think the Ridgid is much sharper.
Scott
While TTI (Techtronic Industries Co. Ltd) owns Ryobi, they do not own Rigid. Emerson Electric Company owns Rigid.
http://www.ttigroup.com/en/our_brands
(Ryobi is listed on TTI’s website as their brand)
http://www.ridgid.com/
(Emerson is shown at the bottom of their website as a link to the parent company)
TTI and Emerson are not divisions of the same company.
Jack
Are brushless drills intrinsically safe
Stuart
I don’t believe so. This is a question to ask tool brands in the context of specific models.
Even if a brushless tool doesn’t have motor brushes, that doesn’t mean the fan, trigger switch, or other electrical components are intrinsically safe. Generally, I believe that if a power tool isn’t explicitly said to be intrinsically safe, it’s best to assume it’s not.
Stuart
You are absolutely right. TTI both designs and manufacturers most if not all Ridgid power tools. I’m not sure about the pneumatics. Because of this, the line between Ridgid and TTI is heavily blurred, which is why many, including myself, often make the mistake of thinking they’re one and the same.
If you look at AEG’s international offerings, you’ll see that most tools are identical to Ridgid’s offerings.
Scott
For anyone googling to this location later, here is a great article about TTI, speaking to the acquisition of Ryobi and the joint venture with Emerson to produce Rigid:
http://www.answers.com/topic/techtronic-industries-company-ltd
Gary McCray
Hi,
In addition to considerably greater power efficiency and more even torque delivery over the entire operating speed range there is one other really important advantage of brushless for power tools.
Power tools are used in really dirty high particulate environments and worse, often high metallic particulate environments.
I personally have destroyed several brushed tools by getting particulates in the brushes during operation. The brushes weld metallic particles to the “commutator” shorting them out and the brush sparks can (and do) ignite wood particulates.
Properly sealed and ventilated brushless motors completely circumvent this problem.
Many modern power tools already include solid state controls and brushless motors can be made smaller and lighter (and eventually with sufficient production cheaper than equivalent brushed motors.
I believe that within 6 or 7 years brushless will completely replace brushed in both hand and stationary power tools.
FYI I am an electronics engineer with my own machine and fab shop.
tom payne
im looking for a rim drive fan. the only one i have ever seen was back in the 70s at a guys house who was an old school computer designer he did not know where he got it.have you heard of anyone making these?
Mark Denovich
The combination of the brushless design and the sophisticated electronic drive circuitry that comes with them can also deliver other benefits like: electronic speed control (the circuitry can vary the current and thus torque to maintain a constant RPM under various loads. My drill/driver of choice does this, enabling me to slowly drive a large screw without having to squeeze the trigger more as more of the screw is engaged. This allows for very precise control just as the screw bottoms out.) Torque sensing electronics can be used to implement a clutch (for driving screws) or as a safety feature (ex: limiting sudden increase in torque, like when drilling a full power and the bit gets stuck) Also by varying the timing/phasing of the current to the motor, the rotation of the motor can be resisted, allowing for the implementation of a electronic motor brake. This is a very nice safety and handling feature in saws and routers, and the soft start/stop makes for easier sanding too (admittedly these examples are usually corded tools, but I know that the better Makita LXT cordless saw has electronic braking.)
tim Rowledge
Brushless motors have been around as a concept for a while but started to appear in the hobby market for model planes about, ooh, 15 years ago. They were *expensive* – my first one was about $400 for a 400W geared motor. As they caught on and the market expanded and the technology for the speed controllers improved, prices tumbled. The ‘out runner’ type where the powered coils are built onto the static shaft and the magnets whirl around in the can made a huge difference because they can be made on the machines that used to wind rotors for old brushed designs. My last high-power brushless out runner purchase can put out around 4hp, takes 70A at 40V is about the size of a stubby coke can and cost… wait for it… $50. Retail.
Small 600W versions can be had for $20.
The electronics are now inexpensive as well; that big motor uses one that cost $90.
I’d anticipate sanders, screwdriver/drills, turbine compressors and maybe routers will go brushless soon.
Scott
I didn’t say in my other posts. Great review of Brushed vs. Brushless motors. I laughed when I found this article today as I was trying to describe the difference today to my wife. We were at Home Depot today ‘playing’ with the drills. The brushless Milwaukees are so much quieter than their brushed li-ion versions. If it wasn’t for their $230 price tag, I would have bought one of the new Milwaukee’s. Instead I bought their cheaper sibling, Ryobi. I used the Ryobi set today and am extremely impressed.
John
I believe that brushless motors run on AC as opposed to DC.
This current is converted to AC by the speed control and there are 3 leads to the motor as opposed to 2 for brushed motors.
eric
Great article and feedback I better sell all my current tools at a loss while they still have any value at all and buy all brushless! Then I can do it again when they run in frictionless magnetic bearings and sealed waterproof to 30 ft depth and heat pipe removal of heat losses!
Bledi
This can be made very simple by stating that there is nothing new to this technology. This is the Induction Motor designed by NIKOLA TESLA, the one used in the workhorse of the industry, the electromotor, with efficiency up to 98%. I thought these power tools motors worked with the same principle, but this industry has been so behind. They have kept this hidden for over a 100 years and have been running with the stupid DC system Motors, that are limited in efficiency and Torque. Why this, because this industry could generate more earnings by making bad products. Now with these new Motors, there is no friction so these Motors can run forever, will never brake. Unless the battery dies. This will kill these companies since people will not need to buy new drills as much as before, in fact much less. So after 100 years after they have run out of ways to improve battery efficiency and increase torque these people are forced against their will to adopt Tesla’s invention which will do what they feared, it will kill their sales. Those who fouhgt against Tesla like Thomas Edison, JP Morgan, Rockefeller and others, feared the same thing. Their business extermination.
DennisEE
Bledi, you need a little bit of education my friend. The brushless motors used in these power tools work TOTALLY different than AC induction motors. Yes, AC induction motors have been around since 1888 and are brushless, but the reason they never took off in the tool market is because your typical AC induction for the same power as universal motors are HUGE and HEAVY. They are huge because the AC line frequency is 60 Hertz in America, which if you know about transformers or AC motors, the lower the frequency, the bigger the motor or transformer will have to be.
Now there are tools that use 400 Hertz AC induction motors and are a hell of a lot more powerful than tools with universal motors, but they are fed with 400 hertz power. They could put in electronics in our 60 Hertz tools that will make the frequency be 400 Hertz, but this would make the tool cost into the thousands of dollars!!! AC induction motors are a lot more harder to control for torque and speed versus brushless DC motors or brushed motors.
Joe Newman
Bledi has a good point though! Obviously it hasn’t escaped the attention of the power tool companies that brushless tools could go on for a long, long loooooooong time HENCE this is WHY they are packing the brushless tools with so much electronics – your motor will be fine but when you find out how much it’s gonna cost to replace electronics in your brushless 5 years after you bought it – guess what – the cost will force you to buy a new one. Just my 2 cents.
Jerome Vernon
Comparisons of AC vs. Brushless DC (BLDC) motor technology typically indicate BLDC motors offer many advantages and few disadvantages.
It is well known that BLDC motors are better for precision motion-control applications. Most current AC powered tools utilizing BLDC incorporate a remote and fairly large power supply unit. Although the remote power supply may be somewhat cumbersome, the advantages of BLDC are nonetheless striking.
Keep in mind that brushless motors can be AC or DC driven however, DC motors provide an EMF feedback to the motor control circuitry for regulation of both speed (amplitude modulation) and torque (pulse-width modulation). Sensory feedback and correction adjustments are made many times per second so one can expect both smooth operation and on-demand raw power without noticeable changes in speed of rotation.
Here is a generalized list of AC vs. BLDC motor Comparisons…
High dynamic response and speed ranges – Torque control is important in various applications where at a given point of time, the motor needs to provide a specific torque regardless of the change in load and speed at which the motor is running. BLDC motors offer superior control over both speed and torque. The main disadvantage of AC motors, when compared with BLDC motors, is that their speed is more difficult to control and torque is essentially unmanageable.
High efficiency – BLDC motors develop more power (torque), per frame size than AC motors so; BLDC motors are far lighter, more compact and highly suited in applications where size, weight, power and speed is crucial.
Less noise and vibration – BLDC motors exhibit less audible noise and vibration because they rely on solid-state circuitry instead of the brush/commutator system of AC motors.
Long operating life – BLDC motors have fewer moving parts and operate more efficiently thus providing greater reliable and longer operating life.
Very Best Regards,
Jerome – Antique Restoration News
Denni
Jerome Vernon, unfortunately you do not know what you are talking about. The “AC motors” with brushes are UNIVERSAL MOTORS, NOT AC MOTORS. AC motors can ONLY WORK ON AC, where as universal motors can work on both.
An AC motor is brushless just like a brushless DC motor and you can have precise torque control with close loop feedback and speed control is accomplished by varying frequency. Finally, AC induction motors can be made much smaller and lighter by raising the frequency design of the motor. A 400 hertz AC motor design is 6 to 10 times smaller and lighter than a 60 Hertz motor design.
joe
Here are some very interesting videos about how motors work.
http://www.youtube.com/watch?v=DGDrOPirFWI
Cristi
Very nice article.
Mike
The reason power tools just started using brushless motors and it’s a reason nobody has brought up,yeah they are more efficient but they are more fragile drop a brushed and brushless drill of a latter and only the brushed drill will work why do think they haven’t used them in corded tools before you rush out and buy brushless think about what tools will benefit being brushless and to me only two tools really benefit and that is circular saw and grinder those two you usually don’t drop but place on the ground drills,impact driver’s abd recip saws I see get tossed around like a bbaseball not good for brushless
matt
What exactly is more fragile? both types of motors are simply something spinning between 2 bearings. Brushed motors for all purposes are more likely damaged from a fall or even more likely from typical debris found on any job sight..
Dropping a drill that is brushless is no more of issue then dropping a brushed drill.. Hell at the end of the day the most likely thing to break on any of the tools you mention is the plastic housing, brushed of bushless doesn’t really matter in that case..
joe
Another fun fact that I recently discovered is about the name “brushes”. Nobody really answered me why they are called “brushes” but when I saw an olddddd DC motor video, I saw a bunch of wires stacked together like a brush on both sides of the motor commutator. They where not carbon made but just a bunch of little strands of wires “brushing” (rubbing) against the commutator….so I put one and two together and that’s how carbon blocks on the the commutators are called “brushes” now…unless someone can correct me but I’m sure that’s how the name “brushes” come to be.
Gene Maglio
I am a millwright in the pulp and paper industry. Our maintenance group uses either Makita brushed or Milwaukee brushless cordless power tools.
There is more power in the Milwaukee’s, but if water gets into the electronics, they need to be repaired.
The Makita’s run through any environmental conditions.
For me, the day to day reliability of a tool in changing environments outweighs power and efficiency.
George Edge
As with so much in electronic parts in vehicles causing much higher maintenance costs once the vehicle ages, I suspect brushless motors will be less reliable over the longer haul due to the electronic elements breaking down and causing people to have to buy new tools. I am still using a drill from 1923, one from the 40s, corded, of course, and my older cordless Makita and Milwaukee continue doing well by rebuilding their NiCad batteries. How long with brushless hold up in comparison? I suspect that even with the Li-ion batteries that the additional electronics in the battery packs will make it impractical to replace the Li-ion cells as the batteries die, requiring more purchases of factory battery packs versus doing one’s own rebuilds. Going brushless can certainly be best in areas where extra power and efficiency are really needed, as with the circular saw and grinder, but who really needs much more efficiency in a small impact or 1/2 hammer drill? I rarely use up my 2AH batteries during any given project with my brushed DeWalt drill or impact, but my brushless circular saw will go through a 4AH battery rather quickly and so it is probably best it be brushless. Also, with some brushless tools, like a cordless circular saw, these would usually not be used a LOT anyway, aside from being used awhile for a given project here and there in an area where a cord is not handy. Who would bother with a cordless circular saw if they have much real work to do, as they are a joke compared to a corded worm drive. Yet, the brushless 7 1/4 circular saw is a useful tool and much better than the older 6 1/2 cordless in brushed motors. One issue I have with brushless drills is that they seem to have no slow speed ability, at least not on my 18V Ridgid brushless drill. Its slowest speed is 130 RPM versus 35 RPM for my 18V DeWalt drill. Slow speed is handy for some operations with a drill to offer good control. Check out the slowest speed you can use a drill at and think about this before you purchase a brushless tool. Maybe this is not a common problem. I sure would not want to do without slow speed on an impact tool used mainly for screws, as 130 RPM would be a bad joke if this is going to be a problem with a brushless impact, but surely this isn’t much of a problem. Even so, control over the speed seems generally better with brushed motors from what I can tell, so far.
Gord Lindsay
Watch a video of a Ryobi RY 40511 brushless 40Volt battery Chainsaw cut up 6″-8″ tree trunks and tell me it won’t cut up a bunch of 2×4 s.
Then watch this video of a RY 40511 disassembled.
I think I’m going to make me a 5″ mini/midi small table saw. Lots of power available – maybe to much.
Gord Lindsay
oops Forgot link http://www.etotheipiplusone.net/?p=3324
Co Rin
Aren’t brushless DC Motors no more than just A/C motors? The DC is converted by mosfits and Zener diodes to simulate AC such as you find in DC to AC power converters.
alexander
Hey, colleagues, didn’t you check Metabo HPT AC Brusdhless range? It is really unique and there is no way in the future to continue with old AC brushed ones…
Of course, that became possible only recently with introduction of new components like IGBT transistors + Hitachi engineers now-how and patents.