Re: (ET) Elec-trak Digest, Vol 13, Issue 80

["David Roden" <etpost drmm net>]

On 6 Jul 2015 at 8:41, Robert wrote:

> Are you sure they limit current by limiting wire size because that a 
> dangerous thing. If more current runs through a wire than its specs, 
> things
> start melting. 

At lower speeds, big series power resistors limit the current.  But from 
speed position #3 or #4 on up, there's really nothing except the wiring's 
resistance to protect you and the tractor.

> You limit current with resistors or with modern electronics (PWM pulse
> width modulation) not with wire size. 

Well, ETs aren't exactly modern.  ;-) 

An EV friend of mine and sometime contributor here calls them "Apollo 
era," 
which is accurate.

If you retrofit an ET with a modern PWM controller, you can replace the 
wiring with larger cable and limit current the modern way.  

However, a lot of ET owners like the fact that they can work on the old GE 
contactor-series-resistance controllers at the component level.  Some of 
them do seem to need a fair bit of work.  Mine certainly did, which is why 
I 
finally junked the GE controller and fitted a PWM.


David Roden - Akron, Ohio, USA

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to the "etpost" address will not reach me.  To send 
me a private message, please use the address shown at the bottom
of this page : http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =