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# Re: [femm] Re: Linear Induction Motors

- To: <femm@yahoogroups.com>
- Subject: Re: [femm] Re: Linear Induction Motors
- From: "Graham Gunderson" <infinitenergy@hotmail.com>
- Date: Mon, 9 Apr 2001 18:23:37 -0700
- References: <9asvp9+caov@eGroups.com>

Hi Adrian, Why not use a linear servo motor? Those have a plunger you can control to the hilt. Also, if you energize a solenoid with a current amplifier you can get more control. (Watch for "shorted turns" in the permeable steel frame, if any - those should be eliminated, or slit so they are no longer a closed loop). Most solenoids are energized with a certain "voltage", or fed by a voltage amplifier (ie, the output voltage is some multiple of the input signal but the amplifier doesn't care about the current it's sourcing, below some overload limit.) Since magnetic fields are of course proportional to current, you can use a current amp (ie, the output currentis some multiple of the input signal, but the amplifier doesn't care about the voltage it's sourcing to get that current, at least within its own compliance headroom.) This gives you way more control. It's also one primary reason why some folksendure the hassle and expense of vacuum tube audio amplifiers (As opposed to solid state) - tube amps are current amplifiers, and solid state amps are voltage amplifiers. Doesn't make much sense to me - if the force on a speaker cone is proportional to the current through the voice coil, why are we usually driving it with a voltage amplifier!!? Graham G. ----- Original Message ----- From: jrt@rosedail.idps.co.uk To: femm@yahoogroups.com Sent: Monday, April 09, 2001 11:41 AM Subject: [femm] Re: Linear Induction Motors `--- In femm@y..., dcm3c@a... wrote: > In a message dated 4/4/01 11:52:45 AM Eastern Daylight Time, > adrianw@s... writes: > > > > Hi, > > I am after controlling the speed the plunger moves at across the whole > > of its travel. Most solenoids accelerate until they hit a mechanical stop, > > I need a bit more control than this. > > > > Adrian > > > > Not knowing much about your application, it's hard to say anything > definitive. However, it sort of sounds like a job for a voice coil actuator > with some feedback. Check out: <A HREF=""http://www.beikimco.com/">http://www.beikimco.com/">http://www.beikimco.com/</A> > > Dave > -- > David Meeker > http://members.aol.com/dcm3c I believe voice coils are relatively short travel - you may do better with a proportional solenoid (travel varies with current) - just search the web with key words 'Proportional Solenoids' and you should find plenty. Cheers John R Taylor` `Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.`

- References:
  - Re: Linear Induction Motors
    - From: jrt@rosedail.idps.co.uk

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