Author Topic: Brushless Motor Explained  (Read 1776 times)

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Offline Mario Turcot

  • Posts: 1228
Brushless Motor Explained
« on: January 24, 2020, 12:17 PM »
I found that video interesting.

What do you think, should we pay more for something that cost less to produce?
Mario

Offline phase3

  • Posts: 17
Re: Brushless Motor Explained
« Reply #1 on: March 16, 2020, 10:25 PM »
Thanks for posting. It's an older post, but I'm a newer forum member, so I've just watched the video.

My opinionated answer to your question: Nope.

But the brushless motors apparently allow the batteries to last longer, when compared with similar torque outputs for brush vs brushless motor. Long-lasting batteries with enough torque for the tool to do the job, that means the previously unmet need is there. For me, the economics is only guesses, because I'm assuming the more expensive (NdFeB?) rare-earth magnets would be used in the brushless motors to allow for the sufficient torque, and that those magnets are these days inexpensive enough that their extra cost isn't significantly impacting the total cost of a motor.

I'm from an I/T background, and the extra charge reminds me of the era when laptops went through eras of glossy and matte displays. There was an upcharge for the other style, but simply depended on which era we were in, not at all on economics of manufacture. (And at the moment I'm using a laptop that I love but a glossy display which I can't stand.) I'll leave out vendors from this example, to avoid a distraction to the thread topic.

I liked most of the video, though I'm going to have to go watch it again to get the detail of the part needing to be multiples of 2n and so I can see why.

Peter

Offline Cheese

  • Posts: 7674
Re: Brushless Motor Explained
« Reply #2 on: March 16, 2020, 11:09 PM »
But the brushless motors apparently allow the batteries to last longer, when compared with similar torque outputs for brush vs brushless motor. Long-lasting batteries with enough torque for the tool to do the job, that means the previously unmet need is there. For me, the economics is only guesses, because I'm assuming the more expensive (NdFeB?) rare-earth magnets would be used in the brushless motors to allow for the sufficient torque, and that those magnets are these days inexpensive enough that their extra cost isn't significantly impacting the total cost of a motor.

To get back to the beginning, Milwaukee released the very first cordless drill in the early sixties. It was tethered to a lead-acid battery that was connected to a 6' umbilical cord. It was cordless in the sense that it could be carried out to the job site and it didn't need to be hooked up to 120V service. However, it did have a short run time and it needed to be recharged several times a day. That was the best that existed at the time.

Then came the NiCad batteries in the 80's.
Then the LIon batteries in the 90's.
And then finally the brushless technology that changed the way in which we work every day of our lives. That has been the over riding change that has changed every work habit in our life.

The cordless Sawzall, the miter saw, the circular saw, the chainsaw, the concrete wet saw have all become viable cordless alternatives because of the brushless motor and the LIon batteries. These are changes that have significantly changed the way in which we work.

I love my old gas powered Stihl 14" cement saw, but the new Milwaukee version is so quiet and so benign.








Offline FestitaMakool

  • Posts: 563
Re: Brushless Motor Explained
« Reply #3 on: March 17, 2020, 01:01 PM »
It is an interesting question. I see brushless versions of tools that are similarly priced as outgoing models. And some more expensive. In the hobby industry the introduction of brushless meant increased prices, in the beginning in particular. Brushless motors spins faster with tighter tolerances and demands more from the bearing holding the shaft. Most brushed motors ride on oilite bronze bushings. Most brushless motors rides on ball bearings. Brushless motors demands more complex electronics, sensored or non sensored motors. I would guess the electronics is more costly. Apart from bushings there may be internal components that are more expensive as well.
But, as a rule as of now, brushed motors are easier to control and gives smoother control on low rpm’s - and better torque at lower rpm’s. Gearing is probably totally different in those two motor configurations. Brushless are most likely run on considerably higher gear ratios to aid low speed torque as these motors excels at high speed.
“The Stig” Yes, it is true, at least some part of it..
“If you have an old Land Rover and a fit wife, you’re most likely always busy”

Offline mwolczko

  • Posts: 56
Re: Brushless Motor Explained
« Reply #4 on: March 17, 2020, 06:50 PM »
something that cost less to produce
Why do you say that?  Rare-earth magnets, precision winding, Hall sensor,  electronics — and the development costs — all have to be recouped.

Offline Mario Turcot

  • Posts: 1228
Re: Brushless Motor Explained
« Reply #5 on: March 17, 2020, 07:20 PM »
something that cost less to produce
Why do you say that?  Rare-earth magnets, precision winding, Hall sensor,  electronics — and the development costs — all have to be recouped.

Have you watched the video?
Mario

Offline mwolczko

  • Posts: 56
Re: Brushless Motor Explained
« Reply #6 on: March 17, 2020, 08:08 PM »
Yes, twice now.  At 5:30 it says that it has a lower MTBF when it should say higher.  At 5:47 it says they are lower cost but nothing to that moment supports the assertion. So the question still stands.

Offline Michael Kellough

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Re: Brushless Motor Explained
« Reply #7 on: March 17, 2020, 08:16 PM »

Offline Rick Christopherson

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Re: Brushless Motor Explained
« Reply #8 on: March 18, 2020, 12:18 AM »
something that cost less to produce
Why do you say that?  Rare-earth magnets, precision winding, Hall sensor,  electronics — and the development costs — all have to be recouped.

Have you watched the video?

Brushless motors have been around for a long time. The reason why we were not seeing them in portable power tools previously is because the cost and complexity of the drive controllers were too high. A universal DC motor can be controlled with a single power transistor, if necessary, but the BLDC motor will require 6 power transistors to develop the stepped-3-phase power signal. The controller also needs to be complex enough to handle the remote commutation of the phase signals to match the rotor position inside the motor. The only reason why these controllers have now gotten to be fairly inexpensive is simply because BLDC motors have become so common.