Brushless tool motors

[Stuey]

Brushless power tool motors vs. Brushed motors via TG

I wrote up a brief description about how brushless motors differ from brushed ones. Milwaukee and Dewalt are soon releasing brushless tools, and I imagine that other major brands have their own upgrades in active development.

Basically, brushless motors are more efficient than brushed ones. Greater efficiency means less current draw and greater runtime, or comparable current draw and greater power output. Most brands will balance things out so that their tools provide more power and runtime.

Expect to see a lot of buzz around "brushless" tools as brands try to dazzle you with their marketing mumbo-jumbo.

 

[mixxmstrmike]

Great primer for what's coming up. I'll be slowly upgrading tools in the near future and it was great to read up on some of the new technology to hit the market.



-Mike

 

[Monte]

Festool + Protool use BL motors for awhile , Panasonic in their impact drivers/wrenches and Hitachi, Makita and Fein already released BL tools too.

 

[pipsters]

They've had brushless motors for R/C equipment for years, I've always wondered what was taking so long in the tool realm.

 

[cashishift]

They've had brushless motors for R/C equipment for years, I've always wondered what was taking so long in the tool realm.

Same.

 

[woody 73]

Question for all the EE Majors out there (Electrical Engineers); in the past when the tool needed it (New brushes) it was a very simple fix and you had the tool up and running.

So this is my question:
When the tool dies do you just throw it away and buy a new one? or can it be fixed and if so would the cost be( higher then a set of new brushes)?

 

[trboxman]

Brushes are a wear item, replace when worn out. I'd imagine that brushless don't have a similar wear item so the question wouldn't quite fit...

 

[woody 73]

I am still a little confused,I can see your point that the two items are different are you saying that when the tool stops you just throw it away?

woody

 

[supra90turbo]

I know from an RC Car standpoint, brush motor vs. brushless is no contest. I wouldn't be surprised to see astronomical torque numbers in electric tools coming in the next few years.

 

[woody 73]

With having that high torque does that mean the motor will outlast the old brush design?
When it does die do you just throw it away?

I ask because if all I need to do is replace a set of brushes and the tool is good for a few more years will the new design keep on going like the commercial the energizer bunny?

 

[Stuey]

Great primer for what's coming up. I'll be slowly upgrading tools in the near future and it was great to read up on some of the new technology to hit the market.



-Mike

Thanks!

With Dewalt's announcement and Milwaukee's pending release, I expect for "brushless" to be as big a buzz-word as "lithium ion" was, and figured I'd preemptively answer the questions that are bound to come up.

Festool + Protool use BL motors for awhile , Panasonic in their impact drivers/wrenches and Hitachi, Makita and Fein already released BL tools too.

True, and I expect that those brands might ramp up their marketing efforts to spread the word.

They've had brushless motors for R/C equipment for years, I've always wondered what was taking so long in the tool realm.

I think what happened is that many brands reached a practical ceiling as to how far they could push brushed motor tech. And with the success of 12V lines, they must have accelerated the development of brushless motor tools some time ago.

Question for all the EE Majors out there (Electrical Engineers); in the past when the tool needed it (New brushes) it was a very simple fix and you had the tool up and running.

So this is my question:
When the tool dies do you just throw it away and buy a new one? or can it be fixed and if so would the cost be( higher then a set of new brushes)?

Brushless means no physical connection other than perhaps axle bearings. So the tool won't just die. I'm not sure if any maintenance will be required at all. I can't see any place there might be a consumable/wearable component.

I know from an RC Car standpoint, brush motor vs. brushless is no contest. I wouldn't be surprised to see astronomical torque numbers in electric tools coming in the next few years.

Maybe. There may be a limit as to how much powerful a cordless tool can be before it becomes uncontrollable. If I had to guess, I'd think that brands will focus more on making tools smaller and more ergonomic than more powerful. Although there's bound to be a boost in power as evident by Dewalt's new impact.

With having that high torque does that mean the motor will outlast the old brush design?
When it does die do you just throw it away?

I ask because if all I need to do is replace a set of brushes and the tool is good for a few more years will the new design keep on going like the commercial the energizer bunny?

It's too soon to tell, but generally I think the answer will be 'yes, the new designs will keep going and going and going..."

The absence of brushes and greater efficiency might also mean cooler operation, which should translate to less wear and tear on the motor as well.

 

[Heavy Metal Doctor]

With having that high torque does that mean the motor will outlast the old brush design?
When it does die do you just throw it away?

I ask because if all I need to do is replace a set of brushes and the tool is good for a few more years will the new design keep on going like the commercial the energizer bunny?

Google is your friend - this kinda spells it out:


http://www.dynetic.com/brushless vs brushed.htm

A brushless motor does not have a mechanical connection (the brushes themselves) to wear. That simple fact makes them more reliable and also allows for higher output since you don't run the risk of power shorting in the cummutator sections and it and the brushes wear.



BTW - Momba Monster / 2650 KV e-buggy on 4cell lipo = nearly undrivable rocket!! I never had a a nitro fly that high!

 

[american lockpicker]

Festool has had this for a while now.

 

[woody 73]

Thanks for the input sounds like brushless is the wave of the future in power tools.

 

[Stuey]

Thanks for the input sounds like brushless is the wave of the future in power tools.

You're very welcome!

 

[2chipped]

I am not a fan of brushless (prefix of dc =brushless with led and a prefix of dw for brushed motors in the 18 volt configuration )...altho the led is nice.

We just decked a dock with 3 in SS screws 2 guys alternating #4 impacts to keep them from overheating with a rotation of#9 batteries....so we work them very hard.
The #1 dc825 crapped out on us ....I get 1 1/2 yrs out of a dw,vs 9 months from a dc .
This is my experience in 7 yrs of using them for fencing, decks/docks, screen rooms/pool enclosures, gazeebos, hand railing,metal roofs,etc...driving everything from#8x 8in screws into marine grade lumber, to 1/2 in screws.
I understand we overwork them, but sometimes you have to work in bad conditions.

 

[Tunger]

I for one am excited about the upcoming brushless revolution. In a brushless setup about the only thing to worry about is bearing failure and I haven't seen any of those in my rc adventures yet, and if the power tool companies partner with someone like castle creations they will end up with an amazing control and the potential for some downright stupid torque figures, if anything we are going to be seeing far more planetary failures than anything.

 

[Stuey]

I am not a fan of brushless (prefix of dc =brushless with led and a prefix of dw for brushed motors in the 18 volt configuration )...altho the led is nice.

We just decked a dock with 3 in SS screws 2 guys alternating #4 impacts to keep them from overheating with a rotation of#9 batteries....so we work them very hard.
The #1 dc825 crapped out on us ....I get 1 1/2 yrs out of a dw,vs 9 months from a dc .
This is my experience in 7 yrs of using them for fencing, decks/docks, screen rooms/pool enclosures, gazeebos, hand railing,metal roofs,etc...driving everything from#8x 8in screws into marine grade lumber, to 1/2 in screws.
I understand we overwork them, but sometimes you have to work in bad conditions.

The DC825 isn't brushless. The "DC" prefix does not refer to brushless either. To my understanding, it stands for "Dewalt Cordless."

Look at a list of the initial 20V lineup - they all have "DC" prefix but none are brushless.

If you overworked your DC825, the new brushless version might actually suit your needs better.

 

[tbobbo]

I am a r/c guy as well. I went from nitro ( fuel) to brushless vehicles about 3 years ago. I went lipo one year ago. No contest.........brushless and lithium combos are so insane. I have been saying that electric tools will replace air tools in the future, and brushless is the next step. I bet the first ones destroy themselves. I took my electric rc truck and converted it to brushless, I also upgraded the transmission. I shredded the gears after my first full pull of the throttle! I must have had the gear mesh off just a bit. With a brushed motor and nmhi batteries I never had to have the gear mesh perfect.
We are going to see some very cool tools coming in the next few years! I bet by 2020 air tools will be inferior.

 

[tbobbo]

Also brushed motors have bearings too and they wear out just like they do in brushless motors. I cant think of one drawback to brushless. Once they are common they will be as cheap as brushed motors.

 

[Greatbear]

I had already posted on ToolGuyd my love for brushless technology and I'm glad it is finally trickling into the mainstream tools. It's about time, and this should be the next step that most the manufacturers make when they update their lines.

 

[cnc-me]

Brushless servo's have been on CNC's for years....

 

[theoldwizard1]

I know from an RC Car standpoint, brush motor vs. brushless is no contest. I wouldn't be surprised to see astronomical torque numbers in electric tools coming in the next few years.

Older brushless motors tended to be high RPM and low torque. Gearing them down produced good torque.

The limiting factor was the cost of the higher current electronic devices (MOSFETs, IGBTs). Looks like they have solved that.

(P.S. Lower cost high power MOSFETs/IGBTs are why the Chinese are making cheap TIG/MIG welders.)

 

[theoldwizard1]

With having that high torque does that mean the motor will outlast the old brush design?
When it does die do you just throw it away?

I ask because if all I need to do is replace a set of brushes and the tool is good for a few more years will the new design keep on going like the commercial the energizer bunny?

Torque required for the application is a major issue. There will be a trade off between more expensive electronics that will handled higher current so that the motor can create more torque, or more gear reduction.

One issue will be the magnets. The motors will likely use "rare earth" magnets. All magnets start loosing their magnetism as they get hot. (Magnets stop being magnetic at the Currie Point temperature which is lower for rare earth magnets.)

The key to the device working or not is the motor controller. It is some "interesting" electronics that reads the output shaft position (which is turning) and the "requested speed" (trigger) and turns on the appropriate coil via an output transistor. All of this (except maybe the trigger and the coils) will likely be built into on device. Replacing this part will be expensive.


FYI - Electric and hybrid electric cars use brushless motors.

 

[theoldwizard1]

Brushless servo's have been on CNC's for years....

A good choice for the application.

Those motors run for many, many hours and brush wear would be an issue.

Space for the motor was not likely an issue. Brushless motor are usually larger.

Additional cost of the motors (including the electronics to run them) was a small compared to the cost of the rest of the machine.

 

[Greatbear]

One issue will be the magnets. The motors will likely use "rare earth" magnets. All magnets start loosing their magnetism as they get hot. (Magnets stop being magnetic at the Currie Point temperature which is lower for rare earth magnets.)

The key to the device working or not is the motor controller. It is some "interesting" electronics that reads the output shaft position (which is turning) and the "requested speed" (trigger) and turns on the appropriate coil via an output transistor. All of this (except maybe the trigger and the coils) will likely be built into on device. Replacing this part will be expensive.


FYI - Electric and hybrid electric cars use brushless motors.

Many of the brush-type motors are using various rare-earth magnets now, the heat buildup hasn't seemed to be an issue in those nor in many other applications. Basically, if you have the motor hot enough to degrade the magnets, there's often smoke involved as well.

Not sure by looking into the simplified pictures given by the manufacturers of these tools with the brushless motors, but most of them seem to be relying on a three phase (six coil) stator and most likely a two pole armature. There are probably Hall-effect devices (usually 3) buried in the stator poles to tell the electronics the angle of the armature. It's possible to skip the HE sensors and use the back EMF from the coils as a position detector, but that wouldn't be feasible in these applications, Such motors have no stall torque and randomly "wobble" until a small amount of speed builds up and the system takes off. That would never fly in a drill.

There is finally a holy trinity that came together to make these tiny brushless motors so awesome. Strongass neodymium magnets, LiIon batteries and low ESR MOSFETs. The latter are amazing. It's possible to have a 30 amp switching transistor the size of a match head that needs minimal, if any, heat sinking. The ones Bosch uses in their 12V line are the same used in aerospace applications.

 

[shampoop]

From what i've gathered they are a waste of money for most people. If you're a carpenter, work in construction, that kind of stuff, the very modest benefits may be worth the huge price difference. Who knows though, in the future new technology may make them as cheap as traditional brushed motors completely replacing them.

 

[theoldwizard1]

There is finally a holy trinity that came together to make these tiny brushless motors so awesome. Strongass neodymium magnets, LiIon batteries and low ESR MOSFETs. The latter are amazing. It's possible to have a 30 amp switching transistor the size of a match head that needs minimal, if any, heat sinking. The ones Bosch uses in their 12V line are the same used in aerospace applications.

WOW !!!

I have been out of the business for a few years and did not realize that things had progressed that far.

Looks like MOSFETs are going to muscling in on IGBT territory !

 

[Stuey]

From what i've gathered they are a waste of money for most people. If you're a carpenter, work in construction, that kind of stuff, the very modest benefits may be worth the huge price difference. Who knows though, in the future new technology may make them as cheap as traditional brushed motors completely replacing them.

The new brushless impact offers more runtime and about 10% greater max-torque. + neat ergonomics and features. Hopefully new drill/drivers will follow with similar gains.

Critics said pretty much the same thing when li-ion batteries came out, that they weren't worth the premium over Ni-Cad packs.

There is a premium built into the price of these tools, but from the numbers I've seen thus far, it amounts to the price of a spare battery.

 

[shampoop]

The new brushless impact offers more runtime and about 10% greater max-torque. + neat ergonomics and features. Hopefully new drill/drivers will follow with similar gains.

Critics said pretty much the same thing when li-ion batteries came out, that they weren't worth the premium over Ni-Cad packs.

There is a premium built into the price of these tools, but from the numbers I've seen thus far, it amounts to the price of a spare battery.

Last i checked less than a year ago, they cost around double what a normal brushed motor impact does. They're fractionally shorter, and fractionally more powerful, and have fractionally better battery life, all for 200% of the price of a traditional one. Definitely not worth it unless you're using it all day every day.

 

[shampoop]

Last i checked less than a year ago, they cost around double what a normal brushed motor impact does. They're fractionally shorter, and fractionally more powerful, and have fractionally better battery life, all for 200% of the price of a traditional one. Definitely not worth it unless you're using it all day every day.

Holy **** prices have dropped! Just checked on amazon and the brushless models are way way cheaper than they used to be.

Brushed -$263

http://www.amazon.com/dp/B0019OZ3HQ/?tag=atomicindus08-20

Brushless $299!!

http://www.amazon.com/dp/B005CQ1N80/?tag=atomicindus08-20

 

[Greatbear]

WOW !!!

I have been out of the business for a few years and did not realize that things had progressed that far.

Looks like MOSFETs are going to muscling in on IGBT territory !

I have to pop open one of my PS-series drivers or drills and take some pictures of the electronics inside. It's very impressive. Luckily there is some conformal coating on the board, the small-scale SMDs used would not take kindly to minute metal chips or water landing on the board, but that has yet to be an issue (for me, at least). The 18V tools have the electronics fully potted in a module located above the battery dock on the bottom of the handle, the PS series have a board just under the motor and above the trigger assembly.

 

[Robbie UK]

With the premium brands fully committed to brushless and with the technology migrating to the cheaper brands prices are really tumbling. With so many plants tooling for brushless kit the brushed motor in power tools may be exiting the scene completely.

 

[Stuey]

Last i checked less than a year ago, they cost around double what a normal brushed motor impact does. They're fractionally shorter, and fractionally more powerful, and have fractionally better battery life, all for 200% of the price of a traditional one. Definitely not worth it unless you're using it all day every day.

Dewalt brushless impact kit is $279. Brushed is $200.

 

[theoldwizard1]

I have to pop open one of my PS-series drivers or drills and take some pictures of the electronics inside. It's very impressive. Luckily there is some conformal coating on the board, the small-scale SMDs used would not take kindly to minute metal chips or water landing on the board, but that has yet to be an issue (for me, at least).

30 years ago I was heavily involved with automotive electronics. At that everything was thru-hole mounted. Double sided boards were "de rigueur" and MOSFETs were still brand new.

The manufacturing guys were really pissed that millions of dollars of thru-hole equipment had to be scrapped when surface mounting became practical and required as complexity kept increasing.

 

[Greatbear]

30 years ago I was heavily involved with automotive electronics. At that everything was thru-hole mounted. Double sided boards were "de rigueur" and MOSFETs were still brand new.

The manufacturing guys were really pissed that millions of dollars of thru-hole equipment had to be scrapped when surface mounting became practical and required as complexity kept increasing.

I had a few minutes tonight so I opened up the first Bosch tool I grabbed out of my Big Bag O' Bosch, a PS41 Impactor.

There is not the least bit of wasted space in these things. The control board is squeezed in between the trigger/direction switch assembly and the motor/gearcase.

This is one side of the control board. The rectangular devices to the right are the two MOSFETS, with a shunt resistor for overload protection on the bottom.

Here is a 1/4" bit holder for reference, these things are tiny, and maybe a millimeter high off the board.

There is more on the flip side of the board.

These control boards are mostly the same in all the recent tools. This one has the three LED battery gauge on it, the PS21s are missing those. There are two MOSFETs here. One is the series pass for the motor speed control. There can easily be 25 amps pushed through that little transistor. The little aluminum heat sink is all that is needed to keep temps in check, and I have yet to notice much heat being given off even when purposely overloading the tools. The motor is what will warm up after a while.

The second MOSFET is one of the reasons I like the Bosch tools so much. It is used as a dynamic braking circuit, shunting across the motor to slow it down. This is not the same as the brake that stops the motor when the trigger is released, that is simply a shorting switch built into the trigger. The dynamic brake works when you have the tool running at a high speed and you release the trigger partially to slow the tool down. When you tip into the throttle a bit, the tool is yanked down to the speed you want, rather then continuing to coast back down to that speed. On some tools without the electric brake (the 1/2" impact is one), you can "manually" brake the tool by releasing the trigger then quickly giving it a little squeeze. That dynamic brake will drop the speed to the slowest available, which is practically a standstill.

 

[theoldwizard1]

I guess only geeky electronics buys like up can appreciate thing like that.

The last automotive powertrain control modules I saw used 6 layer boards. One of the layers is "flexible" so that it acts as board interconnects. 2 or 3 different boards are all built as one and then it is folded into its housing.

 

[Greatbear]

I guess only geeky electronics buys like up can appreciate thing like that.

The last automotive powertrain control modules I saw used 6 layer boards. One of the layers is "flexible" so that it acts as board interconnects. 2 or 3 different boards are all built as one and then it is folded into its housing.

The Siemens ECU in my '03 Mini Cooper S impressed me. As you can probably tell by now, I tend to peek inside the guts of just about everything I own, and then some. I had the ECU out when putting in a new intake, so I had a peek inside. There are two "boards", which were basically a single sheet of kapton attached to two aluminum heat sinks, with a space between that allowed the two sections to fold together. Looked like the stuff I deal with in aerospace. The components were mostly conventional SMD pieces, but the construction was so outside of what I considered "consumer" goods.

Computers these days use localized power supplies on motherboards and such, using pieces once reserved for military and aerospace. A high precision voltage regulator for the CPUs that take 12 volts from the main power supply and bring it down to the 1-1.3 volts used by the high-end CPUs, capable of providing over 100 amps, yet occupying a space on the board about three square inches, and MAYBE has a heat sink. Just the fact the CPUs can **** over 100 amps in some situations is amazing in itself. The technology in cars these days is astounding. It can cause some grief for us indie mechanics, but we eventually adapt.

 

[theoldwizard1]

The technology in cars these days is astounding. It can cause some grief for us indie mechanics, but we eventually adapt.

I used to write the software that goes certain US manufacturers computers. I'm proud that millions and million of cars and trucks had a little piece of my work in them !

I still have friends in the business. The biggest difference now a days is more than 50% (may be as much as 75%) of the code is sensor/actuator monitoring and diagnostics.

The biggest problem in the computer world, from the smallest embedded controller to largest, fastest "mainframe" is obtaining enough, fast memory for an "affordable" price. Caches are nothing but a compromise.

 

[theoldwizard1]

The Siemens ECU in my '03 Mini Cooper S impressed me.

Siemens is out of the ECU business.

The major players are Bosch, Continental and Denso. Denso supplies ECU/PCM to only Japanese companies.

Visteon (formerly Ford) is out of the Powertain Electronics business. Someone bought their facility to continue building some modules until Ford can shift to a different module.

Delphi is still in business, but I don't know who id anyone) is buying their PCMs.


The most common CPU architectures are the PowerPC "Oak" series and the Infineon TriCore.