How was throttling accomplished 100 years ago?

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adric22

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So they were making electric cars 100 years ago. How did the throttle work? Today we use microprocessors to pulse large groups of power transistors at different intervals in order to determine how much amperage we want to go to the electric motor. Obviously that was not how it was done 100 years ago. So how did it work?
 
For a DC electric motor, would you just use a variable resistor?

I think a big spring with a sliding piece of metal maybe?

151332756_WBCI_Variable_Resistor_s.jpg
 
Well they did not go anywhere close to 90 mph. I speculate mostly they ran at full throttle except to start and stop. The resistor would be just to smooth the transition.
 
Yep, that is how many of them worked and how many cheaper golf carts still work today. Various series and parallel combination of batteries. They would also switch in and out very large fixed value resistive elements in some implementations (think of resistive heaters)...


DeaneG said:
Could also have been a sliding switch that selected from various tapped voltages of the battery array.
Click to expand...
 
TonyWilliams said:
For a DC electric motor, would you just use a variable resistor?

I think a big spring with a sliding piece of metal maybe?

151332756_WBCI_Variable_Resistor_s.jpg
Click to expand...

I suspect that thing would melt after about 20 seconds. Too much amperage.
 
DeaneG said:
Could also have been a sliding switch that selected from various tapped voltages of the battery array.
Click to expand...

The cells become unbalanced.. a better way is to split the pack in half and configure the two halves in parallel for low speed and in series for high speed.. that plus switching-in resistors to further reduce speed. I think variable rheostats were limited to very low power motors.. 1/2 hp and such.

Look up how GM did throttle control on their series diesel-electric locomotives in the 20s.. very creative without electronics or power wasting resistors.
 
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!
 
Levenkay said:
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!
Click to expand...

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.
 
i believe they had no real throttle control. it was power on, power off. two different pedals one to go forward, another for reverse.
 
At least some of them DID have throttle control. I've personally seen a motorcycle-style "twist the handle" throttle on a Detroit Electric.

=Smidge=
 
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.
Click to expand...

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/storyofelectrici00martrich/storyofelectrici00martrich_djvu.txt" onclick="window.open(this.href);return false;
 
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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