3phase PWM variable speed motor

You are in the 19th century.The germans have used this since 1990.The ICE train (InterCityExpress) has 13,000 HP, probably 8 traction motors and 2 "locomotives" (see

if you can read german).The motors are asynchronous, three-phase squirrel cage and of course they must have sufficient torque to pull the train at stop and enough rpm to reach the maximum speed of 200 km/h.The cetenary system is 15 kV 16 2/3 Hz.Of course, there's such a drive as in the DVD.In normal electric locomotives there's a motor with brushes and excitation in series (like the one your drill has or your mixer, the one you make the ice-cream) and a transformer with 18 taps.To start the train, you need high current and low voltage.For maximum speed, you need high voltage and sufficient current.These motors are directly coupled on the wheels.

-- Dimitris Tzortzakakis,Iraklion Crete,Greece major in electrical engineering freelance electrician dimtzort AT otenet DOT gr ? "~Dude17~" ?????? ??? ?????? news: snipped-for-privacy@posting.google.com...

The major player in answering this question is "volume" Because the manufacturer can expect to sell millions of thses things,( DVD rom Drives) The development cost can be split, a few dollars over each item with no major impact in the overall price. After the development costs have been covered the manufacturer can then turn a reasonable profit before market saturation.

Not so with larger drives. The thing is there are a lot more "Players" in the motor drive market and in reality, if a maunfacturer goes to market with say a 2KW Drive there are probably more then 30 manufacturers out there each trying for their share of a rather limited market, so the prospective sales will be maybe only in the 1,000's and not the millions that the DVD rom makers have at their disposal.

another factor is PC users tend to have a rather "Geeky" approach to their equipment, with a fair market wanting the Latest and greatest, So they would be perfectily willing to throw away a perfectly good "Widgett" to replace it with another widgett of similar cost but more functions or better specifications. Usually in the industrial drive market, once a device is up and running, There it stays until it breaks or the whole machine is ready for an upgrade.

The other thing is the DVD Rom Drives are a dedicated application, Known Supply Voltage, Known load inertia, One job description. as we all know the application of Variable speed AC Drives has about as many diferent jobs and supply voltages as you immagination can put together. any reputable drive maker must design his drive to be as adaptible as possible so that it can be applied to any of these aapplications. This all adds Cost to the development.

Having said that, there, is no reason why the cost of drives will not fall as time progresses, as we learn how to do things more cost effectively and new technology either takes away some of the obsticales or makes them easier to contend with.

Well there's my 2cents worth.