Follow Slashdot stories on Twitter

 


Forgot your password?
Close
typodupeerror
×
Technology News

Electric Cars as Fast as Ferraris 739

Posted by samzenpus from the how-many-batteries dept.
Ubergrunt writes "A Welsh engineering company has made a motor to be used on electric cars that will make them as fast as a Ferrari. "The motor is revolutionary in that it contains no bulky permanent magnets. Instead it relies on transmitting electric pulses across up to seven rotors, arranged in different phases. These are "fired up" in turn, much like the pistons of an internal combustion engine. There are no gears - the motor provides enough torque at one revolution per minute to put a vehicle into motion - and it spins at up to 2,500rpm. "Size for size, we can provide 400% more torque than any type of motor currently available," says managing director John Bryant."
This discussion has been archived. No new comments can be posted.

Electric Cars as Fast as Ferraris More

Electric Cars as Fast as Ferraris

Comments Filter:

  • Welch? (Score:2, Insightful)

    by Threni ( 635302 )
    It's Welsh. Welch is when you go back on your word. Curiously, the Welsh find this word offensive, but it's a different word and not to be confused with Welsh!
    • They've fixed it now.. but oddly, when I refresh, it sometimes changes back to welch! Maybe not all nodes in the cluster have the new page yet...

    • My local Subaru dealer is The Welch Group (with the 'c'). Obviously they're interested in high performance and powerful vehicles, and they do have several other companies in the group as well as the car dealerships. I was wondering what I'd missed when I went in to get my Scooby serviced the other day...

  • and close down this so fast that nobody will notice
    • I doubt it. Battery limitations will still render this useless for your average family car for some time.

      However I'm sure this could be applied in many other areas of industry where electric motors are already being used.
    • yeah, definatly going strong in the tinfoil department. You know, it's not as if an engine that generates as much torgue wouldn't be a huge competitve advantage to a car producer ...
    • they've got nothing to worry about from this one.


      One disadvantage of this motor compared with PM motors is that it runs pretty high revs to make it's maximum power which implies gearing of some sort.


      If this thing works in reverse it would be a nice basis for a windmill with electronic braking though ! As soon as you hit your target RPM you start firing the motor in the opposite direction.

    • "Who holds back the electric car? Who makes Steve Gutenberg a star? We do, we do, weeee dooooo!!" --The Stonecutters (as if anyone here needs an attribution credit to know that)
    • yeah, sure, its all _one_big_conspiracy_ against the world .. the oil and gas corps are in it together against everyone else ..

      do you _really_ believe that sh*t yourself? People working at oil&gas companies have cars themselves too.

    • Re:the oil and car industry will band together (Score:4, Insightful)

      by MoralHazard ( 447833 ) on Thursday June 02, 2005 @07:47AM (#12703358)
      Insightful? WTF? I think we need a "-1, tinfoil hat club" modifer. Either this is an idiotic comment, or it's an attempt to be funny that kind of fell flat.

      WHY would the car industry want to shut this down? EVERY SINGLE MAJOR CAR MAKER IS BUILDING ELECTRICS as we speak, and most have something on the market at the moment. So far, hybrids that are only somewhat more fuel-efficient than pure gas engines have been a necessary concession, mostly because of performance, range, and infrastructure (fueling) issues.

      If this technology gets off the drawing board and actually works, the car makers will shit themselves to get their hands on licenses because this seems to solve the performance issues, hands down. They'll still have to cope with range and fueling problems, but those have their own solutions coming, sometime.

      And what, exactly, do you expect the oil industry to do to "close this down"? Where on earth would they get the power to do something like that, in a country like the UK?

      Look, oil producers realize that hyper-aggravated prices don't help them, in the long run. That's why OPEC is struggling right now to increase the world supply by upping production, with mixed results. Big Oil wants a stable price, and not too high, either, because it makes the market nervous and causes people to buy less oil in the long run! (It's more complicated than that, but basically that's the story with any commodity.)

      But their inability to increase the supply to meet the higher demand, thereby lowering the price of oil, shows that they CAN'T increase supplies much more. They would probably breathe a sigh of relief if production could go up (which it probably never will), so the only credible scenario to decreasing prices is to decrease demand.

      Big Oil would benefit, in the long run, from a demand for oil that slacks off a bit and then stabilizes (below its current level) for the future. They know this, and aren't going to stand in the way of anything that keeps it from happening.
    • The AC Propulsion Tzero has been blitzing internal combustion engined cars for several years now. They recently switched it to li-ion batteries making it even lighter, faster and now with a 300 mile range.

    • The oil guys I can see (peeking through the tin foil). But the car guys? This could be a motor for just another car. They don't care if it's powered by cow farts, as long as they sell you the car at a profit.
  • "Electric Cars as Fast as Ferrets" ...and I'm thinking, what, tiny electric motors for burrowing robots?

    --
    Toby

  • Obligatory bash quote (Score:5, Funny)

    by AEton ( 654737 ) on Thursday June 02, 2005 @07:09AM (#12703099)
    http://bash.org/?1988 [bash.org]

    <kritical> matts: bikes go faster than cars...a bike at 60 mph is a lot faster than a car at 60 mph
    <matts> kritical: um no...
    <kritical> matts: um yes
    <kritical> my sisters sport car at 60 mph goes faster than my dads explorer at 60 mph
    <kritical> a bike at 60 mph will blow by a car at 60 mph

    • That particular one always reminds me of the folloing line from http://bash.org/?4281 [bash.org]

      [SA]HatfulOfHollow: i'm going to become rich and famous after i invent a device that allows you to stab people in the face over the internet

    • Re:Obligatory bash quote (Score:3, Interesting)

      by ajs ( 35943 )
      I think it's safe to say that when we say, "fast" here, we're talking about the torque that allows for rapid acceleration, not top speed. In car teminology, we're talking about the zero-to-sixty time. In drive experience terms, we're talking about the force of acceleration pinning you to the driver's seat; that sense that you get of "speed" from the rate of acceleration, not velocity.

      If electric cars really can deliver that in a way that surpasses (or even on-par with) internal combustion engines, then I t
      • That has never been the issue. Electric motors deliver their maximum torque at 0 RPM. They are always good at giving torque from launch as long as you have enough electricity to give them (and use a big enough electric motor to begin with, but that's never been a practical issue). Acceleration like that takes a lot of juice, which means the range of the vehicle just dropped significantly. It's the range of the electric cars that has always been their biggest fatal flaw.
        • Just because it delievers equal torque at zero RPM doesn't mean it's delivering maximum power to the wheels at low rpm.

          torque != power. Power = acceleration.

          AIK
          • Just because it delievers equal torque at zero RPM doesn't mean it's delivering maximum power to the wheels at low rpm.

            Not equal, MAXIMUM. And yes, because it does delever maximum torque at low RPM, it does mean it is delevering the type of energy needed to start quickly. Horsepower means how fast you can go. Torque is how fast you can get there.

            For just getting from 0 to 60 as the grandparent was talking about, low RPM torque is the way to go. You don't need torque at higher RPMs unless you are

  • Welch?! (Score:3, Funny)

    by Fross ( 83754 ) on Thursday June 02, 2005 @07:10AM (#12703104)
    And I thought they'd made a motor out of grapes...
  • ...is the loudspeakers to make it sound like a Ferrari. Seriously, that's what I see sports cars used most for, cruising around and showing off, not speeding. The really nasty drivers are always driving around in some styled-up trash, going so fast it's a wonder the nuts and bolts hang together.
    • You mean Gentoo users? :)

      (I'm one myself, but there's nothing wrong with a bit of self-deprecatory humour.)
    • Just because you don't see it doesn't mean it doesn't happen. Albeit, motorcycles seem to be for those who really want to break the speed limit, but cars do as well. You don't see this because if the driver is prudent, they will slow down if they see any oncoming traffic (possible unmarked police car). It is usually the idiot teenagers who drive their shitty cars way too fast (yesterday, a guy at my high school rolled his jeep because, it seems, he was going 80km/h in the parking lot).
    • Actually, when GM came out with their electric vehicle (I worked at Saturn in the same building as the EV1 team)...my thought was the way to dispell the perception that this was some "granola eating tree hugger technology" they should start a racing circuit. They could hit the off season in unconventional venues, (e.g. the now unused Silver Dome). If you had cars going 120mph indoors it would look fast.
    • I remember reading something about a electric motocycle that made virtually no noise. The manufacturer was contemplating adding a speaker to belch out "canned motorcycle sounds" to make the electric motocycle more realistic!
    • That's because those racing Ferrari's aren't competing at the same events as you. But Ferrari's aren't just for racing anyhow.
  • The path to pure electric cars is not in making more powerful motors, but in improving battery technology. Thats not to say that the concept here is not impressive, it is. However, running four of these motors (one for each wheel) is going to draw some SERIOUS juice.

    • Um (Score:2)

      by QMO ( 836285 )
      Using four motors to overcome the same inertia/friction wouldn't take much more power than using one motor to do it. The power would be "spread out."

      If each wheel had an separate motor that could make traction better, make control better, add redundancy in case of a motor failing, etc.

      The problems that I see with having multiple motors are:
      1. Several well-tested techologies for taking power from one motor to 2 or 4 wheels as needed already exist
      2. More breakdowns (even if each breakdown is not as serio

  • Electric motors have always had loads of torque, but having enough to start the vehicle at one (yes, 1) rpm is really impressive.

    • Re:Torque (Score:3, Informative)

      by MichaelSmith ( 789609 )

      To be able to start the car at all it has to have good torque at zero RPM

      • Ever tried to start a regular domestic car (manual) without using the clutch (IE, put it in first, lift the clutch, then turn the key in the ignition). It won't happen. Internal combustion engines have so little torque at 0 RPM that it isn't funny.

        That is what the clutch is for. It lets you get the RPM of the engine up before it has to apply torque.
        • Internal combustion engines have so little torque at 0 RPM that it isn't funny.

          Agreed. I was referring to electric motors.

        • My parents had a pick-up truck that I could start while it was in gear. No problem at all.

          FYI: probably made in the late 70's, International (with the little IH logo in the grill).
    • Unlike typical internal combustion engines, which reach their max. torque at 2000 RPM or more, electric motors can be designed to reach their max. torque from zero RPM. The result is like driving at moderate RPMs and then hitting the accelerator pedal, only you can do it from a standstill. No need for a clutch.

      Also, electric motors that have an astounding power density already exist. An introduction to a particularly interesting design is here:
      http://www.aerodesign.de/peter/2001/LRK350/index_ e ng.html [aerodesign.de]

      T
    • well, 0 rpm I hope. hmmm.

      btw, have you been to a train station lately?

  • Riiight (Score:2, Insightful)

    by 40ozFreak ( 823002 )
    Yeah, I'd like to see that actually bear fruition. Chances are it will either be snubbed by the automotive industry, or will be so damn expensive they won't have a working version in commercial vehicles for 40 years.
  • Won't be fast when you tow the 2,000 lbs of batteries you'll need to keep it running more than 20 miles... Electric vehicles are great, until you consider how to get the power into them...

    Personally, I wouldn't mind if the interstate system was setup with "slots" like the old slot race track toys, for recharging on the go...

    • Re:Hmmm, won't be that fast when you add batteries (Score:4, Interesting)

      by MichaelSmith ( 789609 ) on Thursday June 02, 2005 @07:17AM (#12703153) Homepage Journal
      "slots" like the old slot race track toys, for recharging on the go...

      Vehicle detectors at intersections use induction to count vehicles. If you stop on one you could theoretically use inductive coupling to charge your battery, at the expense of the government.

      I have seen plans for charging up battery and flywheel powered vehicles in this manner, but with more powerfull inductors.

      • Please please PLEASE label them as such. For the love of God and the sake of cyclists - who need to line their metal bike frame right on the telltale loop wound in the pavement, it's the only way to get the light to change at intersections when there's no cars.

        I'd hate to think of what happens to my bike frame and its passenger when the loop in the road starts inducing much field in the frame... I love a good science demo as much as the next person, but this is sadistic!
        • Please please PLEASE label them as such. For the love of God and the sake of cyclists - who need to line their metal bike frame right on the telltale loop wound in the pavement, it's the only way to get the light to change at intersections when there's no cars.

          I am a bike rider myself and I can generally spot the loop without any problems. Usually it has a lot of rubber sealent smeared around on the road surface beside the sawcut. I have seen pictures of lines or pictures painted into the road surface whic

    • Or you could rails at the top and have a massive nation wide bumber car system ..
  • stories about new electric car technology that I always run across the following (from the article):

    "At present, providing enough battery life is a problem. But battery technology is improving all the time, and Mr Bryant does not see it as a major obstacle."

    Yea yea....battery technology is improving all the time. Remember when Li Ion batteries were "memory free"? I hate to be cynical, but I'm starting to wonder if we should be looking for answers other than batteries? I'm sure many of you will be quick
    • Are you thinking what I'm thinking?
      Fission-powered cars?
    • Li-Ion IS memory free.

      Every battery technology wears out eventually, but the gradual decrease in capacity isn't memory. Memory is an effect that only shows up in a specific type of NiCD batteries, and only with very precise charge/discharge cycles, of exactly the same length.

      From what I heard, even on NiCD, the memory effect happens exactly in two places: Satellites, and laboratories. And even labs had trouble accurately reproducing it.

      Batteries can suffer from voltage depression due to overcharge, but t
  • "A Welsh engineering company"

    Just to correct the submitter, we are called Welsh not Welch. Just like people from Scotland are Scots, not Scotch (which is a type of booze).

    • Scotland are Scots, not Scotch (which is a type of booze).

      oh not just a type of booze, it's the ultimate booze! Liquid gold, nay liquid sunlight, nay liquid.... never mind, just drink it and be thankful you're alive...
  • Very clever, using multiple rotors and phases like that.

    While running fast is great, and probably essential for mind-share, I wonder about power consumption. A 1:1 gear ratio seems a little short.

    I forget the details about electric motors. Doesn't power consumption increase with RPM, and so wouldn't a transmission help increase efficiency?

    Efficiency, leading to low power consumption, is the key for an electric passenger vehicle.
    • Doesn't power consumption increase with RPM, and so wouldn't a transmission help increase efficiency?

      No, as long as parasitic loss is kept low (good bearings help a lot) RPM shouldn't matter at all.

      If you run it up to high speed and switch off the power it will ber turning fast and using zero power. The energy you put in only has to offset that lost by the vehicle.

      An IC engine has to burn a mininum amount of fuel in each cylinder for each REV. Electric motors don't have this limitation.

  • It baffles me why people use phrases like "fast as a Ferrari" as a way of comparison.

    Its not hard to make most cars as fast as a Ferrari, Porsche or other neo-exotic. If you think speed is the reason behind them, you have a) never been in one, b) never driven one and c) just don't get it.

    Considering there's a big electric drag race scene, speed isn't something thats an issue with electrics. Batteries is.
    • Its not hard to make most cars as fast as a Ferrari, Porsche or other neo-exotic.

      I call shenanigans. There is nothing you can do to a Toyota Echo, a Ford Explorer, a Ford Focus, or virtually any mass-produced, mainstream general-use vehicle to put it in the same performance realm as either a Ferrari Enzo or a Porsche Carerra GT. By the time you've replaced the engine with the requisite twin-turbocharged, gargantuan 10-cylinder beast (necessary to get a comparable acceleration and top speed) and extended
      • You can call whatever you want, doesn't mean you're right. In fact one of your examples is blatently wrong, a Focus is a car that is commonly upgraded to handling and performance specs that match exotics. You'll be less than sixty grand into it, too. Straight line, you could beat a Ferrari with a bit of work done to a Charger SRT8. I'd bet you could hit it, straight line, under $40k including the car. Hell, with some suspension work, you could probably match the handling. Certainly for under $50k.

        A beat up

  • Put a gas engine on board and hook it to a generator. Output the generator to the electric motor. For 400% more torque, why not? It'd still have a target audience.

    Me, I'm worried about different things. That's a lotta current in square waves being fed into coils. Mucho RF interference. Better bring your MP3 player because your radio isn't going to work very well.


  • At this rate, three and four-hundred mph cars will be just over the horizon.

    Literally, because that only as far as current battery technology will take them.

    (Enters Radio Shack, throws white scarf behind him and pulls off driving gloves. "Hello chap, sixteen-thousand of your best button batteries - just put them in the trunk.")

  • Sweet 60's here I come baby..yeaaaah. Get ready to see an Electric Aston Martin in the next James Bond movie. OK, may be not the next. I bet Austin Powers would switch over too. Now, this post is a total troll!!!

  • Gas turbines have this beat (Score:5, Informative)

    by G4from128k ( 686170 ) on Thursday June 02, 2005 @07:22AM (#12703199)
    The High Pressure Fuel Turbopump on the space shuttle has this power-to-weight ratio beat by a mile. The two-stage, eleven-inch diameter by 3 foot long turbine delivers 75,000 horsepower and weighs about 775 pounds. That works out to 100 hp per pound.

    Of course, you need a supply of liquid hydrogen and oxygen to run the beastie, but if your really need the power, this is the way to get it.

    If LH2 and LOX are too exotic, then try a helicopter gas-turbine. A 600 pound gas turbine can easily provide 5,000 hp.

    The counter-argument is that a gas turbine needs a serious transmission, which adds to the weight of the unit. The counter-counter-argument is that these electric motors need batteries or a motor-gen set which also adds (arguably more) weight to the vehicle.
    • The counter-argument is that a gas turbine needs a serious transmission, which adds to the weight of the unit.

      Also they don't like being throttled down and they especially don't like doing significant work at low revs.

      Science fiction stories from the fifties had jet powered cars in them but the idea died quickly. Perhaps it could be made to work with an electric transmission, and perhaps a generator using Magnetohydrodynamics.


    • The counter-counter-argument is that these electric motors need batteries or a motor-gen set which also adds (arguably more) weight to the vehicle.

      The counter argument is that these electric motors might grab their power out of the air from something like Tesla's wireless AC power transmission.

    • Re:Gas turbines have this beat (Score:5, Interesting)

      by edremy ( 36408 ) on Thursday June 02, 2005 @08:02AM (#12703474) Journal
      But have really, really crappy efficiency in "real world" situations.

      Case in point- the turbine powered M1 tank. Performs like a bat out of hell, at least as far as tanks go, but tanks spend a *lot* of time sitting around idling. I could idle my old M60 for an entire night and still have a nearly full tank in the morning. (In practice you usually run the engine for a short while to recharge batteries and shut down.)

      Now try to do that with an M1- you'll be out of gas in a heartbeat. The problem is so severe that the M1A2 has a second mini-turbine engine just for idling so that it will only drain 3-5 gallons/hour.

      Stop and go traffic with a turbine car will get you something that makes a Hummer limo look like a Prius.

  • When Electric cars become commen place , the national grids i imagine will need to have a serious overhaul due to the added requierments for extra power .
    If we dont move away from fuel sources such coal gas oil etc then we may have just as much poloution albeit more centralised .
    I will have to check into that , but i imagine charging up a battery for one of these things will seriously hike the electricity bill /requierment
    • but i imagine charging up a battery for one of these things will seriously hike the electricity bill /requierment

      In some places you can get cheap power at times when load is low, because generators like to operate at a constant power output.

      The theory is that consumers with access to storage can save money this way, for heating as well as transport.

  • A few weeks ago there was a British team that wanted to break the electric car speed record [thewatt.com] (by driving 252 mph over a distance of at least 1 kilometer). They said that a geared car can achieve 100 mph in a few seconds but their rate of acceleration falls away much more quickly compared to the acceleration of this electric car that can accelerate past the 300 mph mark. Also, electric vehicles have, theoretically at least, infinite torque (at 0 velocity).
    • Are you retarded? They do not have infinite torque at 0 velocity (you mean RPM). They have _maximum_ torque there. If they had infinite torque, that would mean there was no way you could ever stop an electric motor.

      -Jesse
  • Electric cars currently can be Fast enough, go far enough, or be cheap enough for normal people to use. The problem is that it looks like you have to pick two of the three, and normal people want all three. FWIW, the tzero is an electric car that already exists that is as fast (in 1/8 mile drags strip tests) as a ferrari. It also has a decent range...the designers were able to drive from cali to vegas for the SEMA show on a single charge of the lithium ion battery pack.

    The problem is that it costs as

  • Toyota hybrid news? (Score:4, Interesting)

    by islandrain ( 888578 ) on Thursday June 02, 2005 @07:31AM (#12703262) Homepage
    Did you hear about the Toyota hybrid recall that kept stalling because its internal computer didn't know when to switch from electric to gas? Over 33 of them have been found at fault but almost 44,000 have been sold this year. That's not a recall, Ford is the king of recalls. Engine stalling vs. car blowing up. Your call.
  • Some of the advances in technology that have occurred in the last five decades have been really stunning. The advances in chips and computers seem to be the most obvious, but it's almost equally unbelievable what's happened with magnets and motors.

    In the early 1900s the development of small, lightweight fractional-horsepower electric motors that ran on ordinary house current paved the way for a revolution in home appliances. The first "vacuum cleaners" were trucks that drove up to houses with long vacuum h
  • A revolutionary motor just rusting in an old abandoned building. Who is John Galt?
  • electric cars that will make them as fast as a Ferrari....

    when dropped out of a plane
  • The sad thing is, current battery technology will run a decent size electric sedan (not a little pod-car) for 120 miles. This is more than enough daily range for millions of Americans, to say nothing os shorter-commuting Europe.

    If people would warm up to the idea of a little trailer with a gas generator for the occasional over-the road trip we could have a workable solution for many peoples needs.

  • For those that don't know, Wales is a county (like a state or province) in England.

    • Re:Geography. (Score:3, Funny)

      by nagora ( 177841 )
      For those that don't know, Wales is a county (like a state or province) in England.

      For those that really don't know, this is wrong and probably meant as a joke.

      Wales and England are both countries within the United Kingdom of Great Britain and Northern Ireland. Going into a Welsh pub and saying that Wales is a county in England is a good way to be introduced to the National Health System. Imagine telling a Texan that Texas is a county in California...

      TWW

  • Car alternators are around 90% efficient. They do this by having no permanent magnets, like the motor in the story (clue: a generator is just a motor in reverse), so they can carefully control the magnetic field as the shaft speed increases. The only downside is that the field coils need a small power source to initially excite them, which is why you can't bump-start a car with a *totally* dead battery - the alternator won't start producing electricity.

    Bicycle generators [1] are nowhere near as efficient w

  • Similar article (since the link is slashdotted) here [scotsman.com].

    -Adam

  • stupid. (Score:4, Insightful)

    by Eivind ( 15695 ) <eivindorama@gmail.com> on Thursday June 02, 2005 @07:58AM (#12703433) Homepage
    Stupidity poor.

    Sure, a higher power/weight electric engine capable of operation over a wide spectre of speeds is useful. It is not, however, the thing an electric car needs the most to be competitive.

    It's *already* the case that an electric motor is equally strong, or stronger, than a equally heavy internal combustion engine.

    The problem for electric motors is *energy*storage*, typically batteries. With todays tech 400kgs of batteries can store *maybe* a tenth of the energy in a tank of petrol weighing a tent of that, meaning it's 100 times less effective for storing energy.

    To add insult to injusry the 40kg petrol-tank can trivially be refilled in a minute or two, while the battery-pack weighing ten times as much and storing a tenth of the energy, needs hours at best to approach full.

  • FYI: Permanent Magnet Motors (Score:3, Informative)

    by jwdb ( 526327 ) on Thursday June 02, 2005 @09:26AM (#12704337)
    There's nothing revolutionary about a motor with no permanent magnets. PM-less DC motors have existed for decades, using electromagnets in the place. Reluctance motors (?) are similar: they have a multipronged rotor, slightly offset from the magnetic poles, that delivers force by pulsing the electromagnets in series.

    More recently (still at least a decade) AC motors have been growing in popularity, and they work on the principle of magnetic induction. Of course, it's difficult to start one if the rotor is completely demagnitized as it prefers that there's at least a tiny bit of a field, but nontheless...

    Jw

  • How is this new? (Score:3, Informative)

    by greed ( 112493 ) on Thursday June 02, 2005 @10:08AM (#12704807)

    Skipping over all the issues over energy storage that are leading to the success of the hybrid design....

    How is this motor new? They don't describe how multiple rotors are connected. They don't even mention the basic motor technology.

    Not having permanent magnets is not a selling point in Real Motors. Permanent magnet motors are only used in very small, low-power applications--tape player, model car, windshield washer pump, hard disk motor.

    Replacing the permanent magnet with an electromagnet lets you build a MUCH bigger motor. And how you connect it (the field or stator coil) to the rotor coil lets you do neat tricks. It's the motor that made electric rail possible. Same thing is in those old "Mixmaster" mixers, rigged in such a way that they keep constant speed under almost any load. Same sort of motor in your vacuum, blender, power drill, and so on. They're called "DC Machines", but because of the electromagnet, they can run off AC as well (0-60 Hz, it says in the old Mixmaster manual), and are also called "Universal machines".

    But with modern solid-state controls we can do better using various kinds of "AC machines", neither of which use permanent magnets either. An induction machine is your basic steady-speed AC workhorse motor--tablesaw, drill press, washing machine, drier, window fan, fridge or AC compressor, furnace fan. They're weak at start, so tend to come up to speed slowly. An induction machine is basically a lump of aluminum in a changing magnetic field. Set it up with 3-phase AC and you don't need anything at all, set up 3 coils and put a coffee can in the middle and watch it turn. Change the frequency of the AC and you change the speed. For better power, replace the lump of aluminum with actual wound coils shorted together--no brushes, no commutator, no permanent magnet.

    Next is the "synchronous machine", which can be built with a permanent magnet, but you generally don't. You do need sliprings or brushes with this one, as you provide power to a rotating electromagnet. Your car's alternator (and some bikes) use one of these--by adjusting the current through the rotating electromagnet, you adjust the generated voltage. (That's how your charging system regulator works--by changing the amount of power actually generated.)

    You get bags of torque from a synchronous motor, but the problem is getting one to start turning. The classic way is to start it as an induction motor, then engage the rotating electromagnet when it is at speed. If you just start bashing 60 Hz AC into one already in synchronous mode, it will just vibrate, as the magnetic field (still thinking 3-phase) are zipping by faster than it can turn to catch up.

    But with recent (last 10-15 years) improvements in power switching semiconductors, we no longer have to settle with 60 Hz AC. And, on DC supplied vehicles, we have to invert to power a synchronous machine anyway. So, you build a frequency-controlled inverter, so you can start the motor from near-zero Hz and bring it up to whatever speed you want--the synchronous nature of the beast will "lock" it to the speed from the inverter. (And you can watch the power on your drive circuits to see if you are trying to drive it too hard and are about to lose synchronization.) You can do that trick with an induction machine too, but an induction machine relies on the stator windings to induce a magnet in the rotor, so it's not so good at very low frequencies. On the other hand, it starts easily, so you don't need to match frequency to motor speed, it will just "slip". (The difference between syncrhonous speed and actual speed is called slip.)

    One final trick: I've been assuming you've got a 2-pole motor: One north, one south around the outer circle at any given time. At 60 Hz, this gives you 3600 RPM--each time the voltage makes a complete cycle, the rotor has to turn to follow. Another poster [slashdot.org] hit on the right basic idea for electr

Slashdot Top Deals

To be awake is to be alive. -- Henry David Thoreau, in "Walden"

Close