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Nekota
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:01 pm

Levenkay wrote:Uh, it's been a loooong time since the DC Machines classes in college, but I seem to recall that playing with the amount of current running in a motor's field coils had a pretty big influence on the rpm-vs-applied-voltage characteristics. You could use a rheostat to modulate a motor's field strength, and still keep the heating losses in the rheostat fairly negligable, I think. Just don't let the field go to zero!


Yes - the control mechanism would use a small rheostat to control the DC exciter to adjust the power / torque characteristics of a DC motor. Much like an motor amplifier - google 'dc motor exciter' for more details and exciters were more often used for generator sets. Generators and alternators still need exciters but they are 'self exciter' driven - anyone remember having a generator needing a polarity reversal is an example of self excitation in the wrong direction.
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DaveinOlyWA
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Re: How was throttling accomplished 100 years ago?

Thu Jan 26, 2012 6:59 am

i believe they had no real throttle control. it was power on, power off. two different pedals one to go forward, another for reverse.
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Smidge204
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Re: How was throttling accomplished 100 years ago?

Thu Jan 26, 2012 7:34 am

At least some of them DID have throttle control. I've personally seen a motorcycle-style "twist the handle" throttle on a Detroit Electric.

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Nekota
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Re: How was throttling accomplished 100 years ago?

Tue Jan 31, 2012 12:11 am

Some more research brought up this reference in "INDUCTION MOTOR VERSUS PERMANENT MAGNET
SYNCHRONOUS MOTOR IN MOTION CONTROL APPLICATIONS: A COMPARATIVE STUDY" by Jussi Puranen

The first speed-controlled drive was introduced over 100 years ago by Harry Ward Leonard in his
paper “Volts versus ohms – speed regulation of electric motors”. The rotating rectifier consisted of
a grid-supplied induction machine that rotated a DC generator. By adjusting the magnetization of
the DC generator, controllable DC voltage was available for the speed control of a DC motor.
Although three machines were required, it was at the time the only possibility to realize a speed
controlled drive.


Additional reading describes Ward Leonard applied this to elevators, steel rolling mills, and locomotives where additional benefits from regenerative braking are realized. Link --> http://www.archive.org/stream/storyofel ... h_djvu.txt
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GRA
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Re: How was throttling accomplished 100 years ago?

Tue Jan 31, 2012 8:03 pm

Without knowing exactly how they accomplished it, I have read accounts of early EVs which indicate they had several fixed, driver selectable and changeable 'speeds', actually power settings presumably. One car allowed a choice of 3, 6, 9 or 12 mph, IIRR.
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Nubo
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Re: How was throttling accomplished 100 years ago?

Tue Jan 31, 2012 8:12 pm

Perhaps multiple parallel sets of motor windings?
I noticed you're still working with polymers.

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