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Author Topic: What's the deal with non brushless new tools ?  (Read 16466 times)

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Offline acknowlli

  • Posts: 8
Re: What's the deal with non brushless new tools ?
« Reply #30 on: December 08, 2020, 03:17 PM »
I know I am waking up the dead here, but I just can't let it unanswered :) I read the entire thread and ended up astounded  why the simple and straightforward answer just didn't come up :)

The reason corded tools don't have brushless DC motors, is because those can't run on AC from the grid. They need low voltage at a very high current. This is exactly what batteries provide, but the opposite of what the power cord has to offer.

If you had brushless DC motors in a corded tool, you would need to convert low current, high voltage AC power to high current low voltage DC. That means you have to implement an additional power supply, that is bigger and heavier than the BL-DC motor itself.
Brushless motors just don't make sense i a tool running on AC. It would only make the tool bulkier and heavier, with no added benefits.

Mirka has corded sanders with brushless DC motors, to provide a super compact sander with a very low center of gravity. It runs on 48V and comes with a heavy external power supply, that is bigger than the sander itself.
(I know, they are slowly sorting that out, too. But so far the universal motor has the better weight-power ratio when it comes to AC.)

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Offline dallas8338

  • Posts: 22
Re: What's the deal with non brushless new tools ?
« Reply #31 on: December 08, 2020, 03:26 PM »
@acknowlli - The ETS EC is a corded brushless motor and so is the Planex Easy.

Quote from the Festool USA website:
The new ETS EC 150 EQ is perfectly built for manual operation to reduce fatigue when carrying out overhead sanding work and a good feeling on edges, as well as convenient operation in any position. This sander is only 4 1/2" (116 mm) high, contains a brushless EC-TEC motor, and ergonomic housing geometry with perfectly balanced center of gravity. This sander also comes with additional innovative details such as automatic dust control, integrated sanding pad brake, and the unique Vibration Control System for added health benefits.

Offline Pant

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Re: What's the deal with non brushless new tools ?
« Reply #32 on: December 08, 2020, 03:52 PM »
The mirka brushless sander plugs directly into the wall.

Offline acknowlli

  • Posts: 8
Re: What's the deal with non brushless new tools ?
« Reply #33 on: December 08, 2020, 04:18 PM »
Agreed, the Planex has the power supply/motor combination because here it makes sense for improved weight distribution (away from the head). EC makes sense here because of the dustproof design.

Regarding Mirka, yes, as I said they are slowly figuring it out. The brushless sanders had external power supplies for many years. They start getting rid of those now.

Another benefit of BL DC is high torque at low speeds. That makes sense in sanders, because the addet weight from the power supply gets compensated, because you don't need a mechanical gearbox any more.
« Last Edit: December 08, 2020, 04:20 PM by acknowlli »

Offline Alex

  • Posts: 7776
Re: What's the deal with non brushless new tools ?
« Reply #34 on: December 08, 2020, 06:05 PM »
The brushless sanders had external power supplies for many years. They start getting rid of those now.

Those Mirka sanders did not have that external power supply to make the sander brushless. They had that external power supply so the sander could run a on a low voltage and make it suitable for wet sanding.

Offline DeformedTree

  • Posts: 1398
Re: What's the deal with non brushless new tools ?
« Reply #35 on: December 08, 2020, 06:53 PM »
Brushless has nothing to do with hi/lo current. hi/lo voltage.   

Brushless requires a controller, that is the difference.  It's an added cost, an if there isn't a need for it, they are not going to do it.

You design a motor for the need, if you need high torque, it will have high current draws.  Battery tools keep going to higher voltages so they can have more power without more amps.  Corded tools have never had much option, the voltage is either 120 or 230/240VAC.


Offline acknowlli

  • Posts: 8
Re: What's the deal with non brushless new tools ?
« Reply #36 on: December 08, 2020, 07:19 PM »
Ok, that sounds interesting. Mirka has replaced the entire Ceros series (external supply) with the newer Deros (internal power supply). Does that mean Mirka doesn't offer electric sanders suitable for wet sanding anymore?

Just curious :)

Offline Bohdan

  • Posts: 1018
Re: What's the deal with non brushless new tools ?
« Reply #37 on: December 08, 2020, 07:34 PM »
There is a fundamental difference in performance between brushed and brushless motors. The brushless motor is an induction motor so if it is overloaded, by being pushed too hard, it will drop out of sync and stall.

On the other hand a brushed motor will simply draw more current and keep going, for a short time untill it overheats and burns out.

This means that, for the same user performance, a brushless motor needs to be nearly twice the wattage rating.

This doesn't mean that a BL motor will use more power. Both motors will use roughly the same power for the same job but the B motor can easily exceed its rating if required. In battery tools a BL is more efficient, and has more torque at low speed, so the battery lasts longer.

Comparing the wattage rating between B and BL motors will not give you any indication of how they will perform in a power tool in actual use.

To prevent burnout on brushed motors manufacturers fit temp sensors which, like on the TS55, shut them down until they cool down.

Offline Rick Christopherson

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Re: What's the deal with non brushless new tools ?
« Reply #38 on: December 08, 2020, 07:38 PM »
There is a fundamental difference in performance between brushed and brushless motors. The brushless motor is an induction motor so if it is overloaded, by being pushed too hard, it will drop out of sync and stall.

As I already pointed out 2 years ago, brushless motors (specifically BLDC) are NOT induction motors, and these conclusions are therefore not correct.

Offline Alex

  • Posts: 7776
Re: What's the deal with non brushless new tools ?
« Reply #39 on: December 08, 2020, 07:38 PM »
Brushless requires a controller, that is the difference.  It's an added cost, an if there isn't a need for it, they are not going to do it.

There is a need for it because people want it. People want quiter motors that are more controllable and run smoother. Added cost? Hmm, not sure about that. Pretty sure that controller will soon be on a single chip costing 50 cents. Of course it costs a bit more now it is still new.

I remember how I bought my first hard disk drive back in 1997. Quantum Fireball 6,4 GB, top of the line back then. Paid €200 for it. Now you can buy a 2TB SSD for only €134. It has 300 times the capacity, 1/100th the size, and works about 80-100 times faster.

  Corded tools have never had much option, the voltage is either 120 or 230/240VAC.

Not much option? My smallest 220 volt tool draws 80 watts, my biggest 2600. Try that with your 36v batteries.

Offline Alex

  • Posts: 7776
Re: What's the deal with non brushless new tools ?
« Reply #40 on: December 08, 2020, 07:43 PM »
Ok, that sounds interesting. Mirka has replaced the entire Ceros series (external supply) with the newer Deros (internal power supply). Does that mean Mirka doesn't offer electric sanders suitable for wet sanding anymore?

Probably. I am not that familiar with Mirka's entire line. But I grew up in a body shop, and it was clear that Mirka wanted to offer their electric sanders as a replacement for the air sanders used in that sector, that's why they made them look exactly the same. When you work up your grits and you go above 800 you go over to wet sanding. Not a problem with an air sander, but not allowed with 220v electrical sanders. So they had to think up something, and the transformer was the answer. It was already used by diamond drills with water cooling and tile cutters.

But it is not hard to see people didn't like the separate transformer. Why carry two lumps around when you can just plug an air sander into your compressor line?

Smart move by Mirka to get rid of it. Their sanders are pretty popular now.

Offline acknowlli

  • Posts: 8
Re: What's the deal with non brushless new tools ?
« Reply #41 on: December 08, 2020, 07:52 PM »
Water cooled drills and cutters use an isolation transformer, so that the 230V coming out of it isn't referenced to ground, but floating. That prevents electric shock when touching a live wire while standing on conductive ground.
 
The low voltage DC power supply Mirka used for their Ceros sanders is an entirely different animal.

Offline Cheese

  • Posts: 9676
Re: What's the deal with non brushless new tools ?
« Reply #42 on: December 08, 2020, 10:18 PM »
Interesting...I went to wet sanding at the 400 level.

From my era, I’d use 400 grit on bare steel to abrade it down to a 500/600/800 level, who knows what level it was at, all we knew was that it was more than 400 grit.

30 years ago we didn’t have the luxury of choosing a 1200/2000 grit paper, it was simply a 3M Wet or Dry 400 paper worn out sanding steel. That was the best of the best.  [big grin]
« Last Edit: December 09, 2020, 09:35 AM by Cheese »

Offline Alex

  • Posts: 7776
Re: What's the deal with non brushless new tools ?
« Reply #43 on: December 09, 2020, 03:31 AM »
Cheese, you can wet sand at any level you want. When you get in the higher grits, the change is not as big as in the lower grits. The difference between 120 and 240 is bigger than between 400 and 800.

In the body shop we had a rack full of the black waterproof 3M paper, it ranged something like 400, 600, 800, 1200, 1600, 2000. Can't remember exactly anymore, that was around 40 years ago, but we had a lot of grits to choose from.