[ausev] Riding close to 96v EMF vs 120v EMF

[Charlesvsi at aol.com]

As I remember it, EMF is created by a change in current flow. A clutch has  
moving metal clutch plate pulled in by a switch on ( square wave of current) of 
 voltage through the coil/solenoid  windings, The square wave creates  
multiple frequency EMF and when the voltage is removed at clutch release, the  
rapidly collapsing magnetic field creates a massive EMF field change creating  back 
EMF surge that can be very high voltage and again high frequency noise etc. 
 
This is similar to Process Control systems with relay solenoids switched on  
and off. Most now have suppression circuits with resistors, capacitors, and  
diodes to absorb or damp the current surge, reducing EMF noise. 
 
Modern dc current switching is done by transistors, often by using pulse  
width control, short pulses create low average current and slow motor operation  
and wider pulses creates high average current and full current power. Back in  
60's Sperry Phoenix built a pulse width controller for the B52 rudder bob 
weight  motor. I did the circuit component tweaking and shake testing,  RF, and  
temperature testing etc. With power transistor switches, no heat loss, and low 
 control voltage and current allowing cheap reliable components for speed  
control. 
 
I don't know how the modern Electric vehicle controllers work. If by pulse  
width control, applying additional voltage to the motor circuit would be  
dangerous, unknown surges, etc. 
 
On radiated EMF, again it depends if power control is analog with voltage  
slowly changing from 0 volts to maximum output of battery. There would be  
minimum lost EMF and radiation. 
 
If pulse width control, the switching circuits and constantly changing  
pulses applied to motor windings would create much EMF radiation from wires,  
windings, etc. It can be absorbed pretty easily, but would need to be tested for  
and suppression circuits added.
 
Where could I get the schematic for a controller? I'd assume they are  
designed and tested as a package with design limits that must not be exceeded.  
Better to buy the package of batteries and controllers for maximum power/speed  
needed. Multiple winding motors sounds expensive and complicated. 
 
Chuck Simms. 
 
In a message dated 11/7/2006 5:19:26 P.M. Central Standard Time,  jtp at onr.com 
writes:

Mark,
We had discussed 4 years ago (when you had offices in San  Marcos),
regarding an electric motorcycle and sitting to the close  proximity to the
motors' EMF, that,  a copper mesh-surround-to-ground  may be the direction to
go within the fiberglass body housing over the  motor, to ground magnetic
fields. To what extent might that be  effective?
I'm sure that some emf would get through, as I've noticed a  compass needle
swing from north-magnetic to point to the electomagnetic  clutch (in my
motorhome) when the a/c compressor is engaged, (a foot away  from the
compass).
Is there any great difference in  voltages applied in the production of
field strength, or is it a matter of  watts from  demand?
Dan.

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Chuck Simms

Director, North Austin M.U.District  #1
e-mail: charlesvsi at aol.com
Phone: 512-331-9630
Cell:  505-331-1237
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