Re: (ET) Speed controller

["David Roden (Akron OH USA)" <roden ald net>]

> If you connected the field in parallel with the armature, you'd have
>     two
> competing effects that would turn your motor into a nearly constant speed
> motor. 

Yes -- of course.  That makes complete sense.  The old PMC DCC-72/96C 
shunt/compound controllers used constant field PWM up to something like 
half pedal, then began reducing the duty cycle.

I retract my remark about Curtis's old instructions for shunt / compound 
motors.  I should have checked the manual.  Here it is, verbatim from my 
old PMC-25 manual:  

"The PMC does not provide current for separately excited fields such as 
those found in shunt and compound motors, and may be considered as being 
specifically designed for series-wound motors.  However, the controller 
may be used with shunt and compound motors if a separate source of field 
current is provided.  For motors with shunt fields woiund for full 
battery voltage, the shunt field may be connected across the entire 
battery pack via a contactor.  In such installations, a "freewheeling 
diode" should be installed across the field to prevent arcing across the 
contactor as it opens.  For motors with fields wound for less than full 
battery voltage, or in cases where field control is desired, either a 
separate transisotr field controller is required, or the field may be 
connected to various taps off of the main battery pack.

"When a series winding is not provided in the motor, such as in a pure 
shunt motor, an inductor must be added in series with the armature in 
order to provide the inductance would would normally be supplied by the 
series winding.  High current inductors (part number IND-100) are 
available from youir PMC dealer."

I stand (humbly) corrected.

As has been pointed out here, Curtis does make sep-ex controllers.  So 
does Zapi, an Italian manufacturer.  There is also a sep-ex controller 
made for Yamaha golf cars, but I don't know if it's adapable to the ET.  
Sorry to say I have no experience with any of these.  If you do, please 
share it!


David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak E15 36vdc