
As Electric Motors Impove, More Things Are Being Electrified - jkuria
https://www.economist.com/news/science-and-technology/21728888-better-motors-go-better-batteries-electric-motors-improve-more-things
======
Animats
Yes, there's action in rotating electrical machinery again. For decades, this
was a dull and boring field.

Tesla and Steinmetz figured out the theory of AC machines in the early 20th
century. This was the first industrial technology where you needed advanced
math to get anything to work right. Complex numbers. Calculus. Laplace
transforms. That bothered some people, such as Edison. By the 1930s it was
figured out, and generations of EEs struggled through rotating machine theory
in college.

Then all the cool kids went off to radio and transistors and computers.
Rotating electrical machinery was a mature field. Maybe a few people at GE in
Schenectady worked on it.

Then came power semiconductors, and chopper-type motor control, where power
was being turned on and off at moderately high frequencies. At first this was
just applied to existing motor designs. But AC motors were designed for sine
wave power. Choppers didn't produce clean sine waves. Much effort was put into
making variable-speed controls that produced the nice sine waves motors
needed. Classical AC theory was built around sine waves, and engineers knew
how to do that kind of analysis. This worked, but it made AC motors buzz at
the chopper frequency, and as chopper frequencies went up, whine. When you
ride on BART, that's what you're hearing from the motors. The waveform
mismatch also led to unwanted heating in the windings and inefficiency.

Variable-frequency 3-phase AC motors went from exotic to normal. Today,
everything from a Tesla to a drone to a Diesel-electric locomotive uses such
motors. The big power semiconductors required aren't that big. Here's one for
a locomotive.[1]

In recent years, motors have started to be designed for the non sinusoidal
waveforms that come out of chopper power supplies. This required new theory
and much simulation of magnetic fields. There's plenty of compute power
available and commercial packages for that kind of analysis. Now we're seeing
more advanced motor designs that match well with their control electronics.

After most of a century, rotating electrical machinery design is cool again.

[1]
[http://www.ametrade.com/eng/electronics/products/IGBT_IGCT.s...](http://www.ametrade.com/eng/electronics/products/IGBT_IGCT.shtml)

~~~
hwillis
>When you ride on BART, that's what you're hearing from the motors.

[https://www.youtube.com/watch?v=vdNCrj14cK0](https://www.youtube.com/watch?v=vdNCrj14cK0)

~~~
twic
That's brilliant!

There are some trains on the London Underground that use gate turn-off
thyristors, which make a sort of Star Trek klaxon sound when they start up:

[https://www.youtube.com/watch?v=pagB58tGpRY](https://www.youtube.com/watch?v=pagB58tGpRY)

~~~
hwillis
My favorite bit of electric locomotive technology:
[https://www.youtube.com/watch?v=yjMZ5qtyCUc](https://www.youtube.com/watch?v=yjMZ5qtyCUc)

Closely followed by dynamic braking, or as it is more accurately and much more
awesomely called in the UK, rheostatic braking.

~~~
toomuchtodo
Someone posted one of these on /r/electricians the other day running an
elevator in New Zealand; very cool piece of tech.

[https://www.reddit.com/r/electricians/comments/6vpg8n/the_me...](https://www.reddit.com/r/electricians/comments/6vpg8n/the_mercury_arc_rectifier_that_powers_the_durie/)

------
hwillis
Pretty bad article. Its conclusions are broadly correct, but the way it gets
there is not. There hasn't been any major change in motors- the major change
has come in Variable Frequency Drives (VFDs). Older motors are hooked directly
into the grid and deal poorly with changing speed and torque, and can drop
_drastically_ in efficiency. A motor can be 60% efficient at low load, and 98%
efficient at its rated load.

VFDs are very complex pieces of circuitry- far more than you'd expect.
Efficient drivers require a great deal of computation, and 16 or 32 bit
processors are not uncommon. That also requires high-power, _cheap_ silicon
transistors which are only gradually taking over from simpler control schemes.
They make a huge difference in a lot of cases.

The author is also very wrong on Synchronous Reluctance-assisted Permanent
Magnet motors, but its hard to fault them on that; it's complicated even for
many engineers. The purpose is not to increase the power density, it's to
increase efficiency. The magnets act like a "cruise" motor. At low torque,
they provide all of the rotor magnetization at a very high efficiency. At
higher torque, the stator induces a stronger field into the rotor, causing it
to act like a reluctance motor. That allows you to turn on extra power as
demanded at the price of lower efficiency (the same as a reluctance motor).

If, instead, you just used a larger PM motor, it would be more expensive and
it would also have an efficiency drop at low torque (where the motor spends
most of its time operating). The magnets are highly efficient but they "set"
the operating torque of the motor somewhat, so there is a loss at low
power/high speed to hysteresis. A reluctance motor meanwhile never reaches the
peak efficiency of a PM motor.

Anyway the article doesn't really say much convincing and feels mostly like
fluff.

~~~
agumonkey
Here's some comparison
[https://www.youtube.com/watch?v=ZOH1PoOOeuY](https://www.youtube.com/watch?v=ZOH1PoOOeuY)

~~~
hwillis
Great video! NB to anyone watching that this is a standard reluctance motor,
not one with magnets like the one in the article.

------
bronz
you ought to get into the habit of looking at a spectral analysis of the sound
in your home. modern power supplies and motors rely on the ever more powerful
and cheap power transistors that we have these days -- they are able to switch
power on and off at very high frequencies and thus reduce the size of the rest
of the circuitry needed to raise or lower voltage. but this often results in
extremely high pitched sound coming from parts that, for whatever reason,
physically move or expand in response to current or voltage changes. in cheap
electronics, this effect is not accounted for and controlled with vibration
dampening materials applied to the vibrating parts, and the result is a
maddening high pitched squeal. even if humans arent able to hear it, there
could be devices in your house that make some kinds of pets uncomfortable. ive
been meaning to buy something that will let me detect ultrasonic sound so that
i can smash those devices with a hammer.

ive always wondered what it would be like if you used a dual motor system in a
car, where one motor is wound and sized for very high torque and the other
motor is wound and sized for very high speed. i think it would be great
because, as long as they were induction based motors, you could run one and
leave the other off with no interference from the one that is turned off. it
would be like having a transmission without any of the energy loss or
maintenance problems. you could also distribute power however you want among
the two motors, and in a way have something like an infinitely variable
transmission. that would be really cool.

~~~
pbasista
_I 've always wondered what it would be like if you used a dual motor system
in a car, where one motor is wound and sized for very high torque and the
other motor is wound and sized for very high speed._

The dual motor versions (D) of Tesla electric vehicles (models S and X at
least) use this principle. As far as I know, they have induction motors.
However, I am not sure to which extent one of the motors is used primarily for
high torque and the other for high speed.

~~~
vvanders
Yup, the front motor is the cruising motor and the rear one is the
accelerating one(since weight distribution means that the rear wheels get a
bit more traction).

They shut the rear motor down at highway speeds giving the Dual Motor cars
slightly better range.

~~~
MBCook
Do the single motorcars only have one of those two? If so which?

Or do they have a third kind of motor which is wound to be a better balance?

~~~
vvanders
My understanding is that there's 3 configurations

Single motor, non-P: 1 large motor in the rear.

Dual motor, non-P: 2 small motors in front/rear with front motor geared for
cruising, rear for accel.

Dual motor, Performance: 1 small motor in front geared for cruising, one large
motor in the rear.

There's really no reason to have a front motor only. It's done in ICE cars to
save cost/complexity since the engine is up front. With how the center of
gravity shifts during accel you want the drive wheels to be on the rear since
they have better traction.

Same reason in reverse you have large disk brakes on the front wheels and drum
in the rear.

~~~
ars
> you want the drive wheels to be on the rear since they have better traction.

But you need a powerful motor to act as the brake (you want to avoid friction
braking as much as possible). And that needs to be in the front.

~~~
vvanders
Not really, unless you're in a panic brake situation(where I want friction
brakes anyway) Tesla only brakes to 60kW which is more than plenty for normal
driving.

You also want friction braking for cases where you've got 100% charge or the
battery is cold and you can't dump energy into the pack.

------
cmrdporcupine
Expense of motors (not to mention batteries to support them) is still a
problem with electrifying smaller equipment. I was looking at repowering one
of my old 12hp Gravely walk-behind tractors -- to find an equivalent torque /
HP EV motor to replace the Kohler 301 in it would have been upwards of $2-3k.
And that's not including sourcing batteries, supporting electronics, etc. A
little diesel engine would be about $600.

I hope to see the day when projects like this could be cost effective.

~~~
Gibbon1
Where you likely want to search for affordable electric motors is 'electric
golf cart motors'. When I was looking at refurbishing a golf cart in the early
2000's I was a bit surprised to see high performance brushless dc motors being
used.

~~~
jpindar
Also forklift motors. I don't know about the price, but I've heard of them
being used to build experimental electric vehicles.

------
pankajdoharey
What is there to improve in motors ? They are already 95% efficient, and some
BLDC motors even 99% efficient. The most efficient machinery created by man.
What really needs improvement are battery storage, to be more dense and
lightweight.

~~~
elementalest
I worked for a BLDC company in their research division for a few years and
there are many things that can still be improved. At the time we were working
on reducing the size of motors without sacrificing torque or efficiency. This
was particularly the case for industry motors where we developing a motor half
the size of an older industry standard AC motor, but with the same power and
94% efficiency.

Size is where the majority of advancements for BLDC motors will come.

~~~
nerpderp83
Advances in size and weight is what will enable innovation in new applications
of motors.

------
bostik
Nice to see Visedo getting recognition.

They are essentially an offshoot from the decision made nearly 20 years ago:
Lappeenranta University of Technology decided to focus on energy tech, and
added environmental tech as a second leg a few years later. Visedo is one of
the results.

I also remember, while their offices were still in the tech incubator
warehouse, trying out their prototype electric "car". Lightweight, all sheet
metal, uncomfortable to sit in and steer - but went from stand-still to
~50km/h in no time at all. Looks like they've managed to scale up and refine
their technology quite a bit since then.

------
mrfusion
Is anyone researching motors that use elerctric charge instead of magnetism?
Couldnt those be cheaper to build and possibly more efficient and powerful?

~~~
hwillis
> Is anyone researching motors that use elerctric charge instead of magnetism?
> Couldnt those be cheaper to build and possibly more efficient and powerful?

In general the magnetic permeability of materials is 1-3 orders of magnitude
higher than the electrical permittivity. Materials with high permeability are
also 2-3 orders of magnitude cheaper than materials with high permittivity. It
makes much more sense to make magnetic motors because of those two facts.

However charge-based motors have existed since the mid 1700s[1]. They're
exclusively novelties, but they are exceptional novelties indeed. You can even
use a kite to power them from atmospheric electricity[2]! That's the same
voltage difference that eventually creates lightning, but without a storm the
electricity is quite weak and the motor quite inefficient. The voltage is high
enough to be unpleasant though.

[1]:
[https://en.wikipedia.org/wiki/Electrostatic_motor](https://en.wikipedia.org/wiki/Electrostatic_motor)

[2]:
[https://www.youtube.com/watch?v=qhXxSAv6rMg](https://www.youtube.com/watch?v=qhXxSAv6rMg)

------
falsedan
Typo in article submission title

> _As Electric Motors Impove,_

------
erikb
I'm surprised to read in an age of LEDs lightning is supposed to use more
electricity than computers. I'm not even sure that on average the motor uses
that much more energy than all the other appliances in an electrical car.

~~~
wongarsu
Even LED lights have a typical efficiency of only 10-20%. Low pressure sodium
lamps (many yellow street lights) can reach 30% efficiency. But in general,
lighting is far from being a solved problem even if you assume everyone is
using state-of-the art lighting solutions.

~~~
erikb
Yes, but that doesn't explain why all the computing we are doing should spend
less electricity than light. I bet I can run all the light in my apartment for
24 hours and don't use as much energy as when I'm playing a AAA 3D computer
game for an hour.

~~~
wongarsu
If you play your AAA game on a PS4, that's about 120W [1].

Assuming you have three 60W-equivalent light bulbs on in your appartment,
using halogen lamps your lights use as much power as the PS4. If you still use
incandescent lamps, that's 180W, about as much as much as the PS4 and a 55"
LED TV. With 7W LED bulbs you need 5 hours of lighting to match the PS4, or 8
hours to match PS4+TV.

Of course you might have a computer that uses significantly more power. But
the best current-get Intel i7 still has a TDP of only 112W (165W for i9). Add
to that a GeForce GTX 1080 TI with a TDP of 250W. Even during gameplay both
will on average use less power than their TDP. Without going with dual-GPU
configurations you can't build a reasonable current-gen computer that matches
the 500Wh that our three 7W LED use over 24h. And I suspect you actually have
more than three light bulbs.

1:
[https://en.wikipedia.org/wiki/PlayStation_4_technical_specif...](https://en.wikipedia.org/wiki/PlayStation_4_technical_specifications#Power_usage)

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bradknowles
Impove?

I think that's a spelling error. ;)

------
addHocker
I know its kind of a ofshot question- but is there research in non-chemical
batterys? As in storing energy mechanically in nano-structures? Goggle did not
reveal much there.

~~~
hwillis
Batteries are chemical by definition. The closest thing to storing energy in
nanostructures would be nonchemical supercapacitors, which use nanostructures
or nanofabrication to achieve high surface areas. As a side effect of
electrical attraction they store some energy mechanically too.

In general storing mechanical energy at the nanoscale is not efficient. As you
get smaller mechanical properties become less relevant due to the increase in
relative surface area (aka square-cube law). That makes electrical and
chemical properties much more powerful.

