[Spridgets] Tesla--the electric Lotus Elise

[Bruce Lowry]

Resistors are old tech!
Newer type is a "chopper" circuit that actually turns power on and off for 
an average power.
It uses too much energy and makes heat which is bad.
Mechanical switches and brushes...primitive but effective.
Even newer tech is a transistorised version that can modulate the frequency 
and the width for these power pulses (on or off).
These cause the growl or whistle you hear as the motor revs up.
Newest works on the same principle but uses MOSFETS (metal oxide 
semiconductor field effect transistors) which still work on the same chopper 
effect, but with greater efficiency and control over the pulse width and 
frequency. These are used on all those little wheelchair things running 
around.
These can be adjusted for load so that when we "floor it" it doesn't just go 
to the highest setting and snap axles.
I was going to build a hybrid in a 66 Sprite, but could not bring myself to 
do the cutting nessesary.
Now I have a 95 Aspire that may get the nod.

Bruce


> That's true.  I do maintenence on a 15HP DC motor (GREAT BIG sucker) that
> runs a blower.  To get it to start up without that shock, current first 
> goes
> through a bank of resistors, that drop off one at a time until it's up to
> full speed.  Just like the trolleys did with the motorman handling the
> controller and on later trolley cars with a foot throttle.
>
> I wonder if the automobiles have the banks of resistors to insure a 
> gradual
> start up or if it's being done a newer way today?  Anyone know?
>
> Paul A