Re: (ET) E-15 Reverse relay Arcing

["Rod Hower" <Rod Hower ametek com>]

Check out my schematic for the proper placement of freewheel diodes and
transzorbs.
http://www.qsl.net/w8rnh/etrakh/ELECTRAK.PDF
(the server seems to be down right now though?)

This should eliminate most sparking of the relay IF you come to a complete
stop before
switching directions.
When I wrote software for a compound wound forklift drive motor I had a
similar problem.
When you switch direction of an electric forklift you typically
electronically brake by 'plugging' the motor.
You could quickly switch between plugging to opposite direction on a series
wound motor.
The compound wound motor required a 100 mS delay to allow the shunt field
current to decay otherwise
a huge surge current would flow.
This is similar to what can happen when switching direction on the ET while
it's still moving in one
direction and you reverse without stopping.
Rod Hower - Senior Project Engineer
Ametek Technical Products Engineering
627 Lake Street
Kent, OH 44240-2660
(330) 677-3875
(330) 677-3306 Fax
rod hower ametek com
USA
www.ametektmd.com


                                                                           
                                   
                      Dave & Debbie Barden                                 
                                   
                      <daveb seanet com>               To:       
<ssawtelle fcc net>,                         
                      Sent by:                          <elec-trak cosmos 
phy tufts edu>                      
                      owner-elec-trak cosmos ph        cc:                 
                                   
                      y.tufts.edu                      Subject:  Re: (ET) 
E-15 Reverse relay Arcing           
                                                                           
                                   
                                                                           
                                   
                      05/02/03 03:40 AM                                    
                                   
                                                                           
                                   
                                                                           
                                   




I have an E12 with this same problem.  Admittedly still unsolved.  after
repairing the relay several times it finally fused together beyond repair.

before putting in the Bill Gunn version ($20) I came across the Hosfelt
catalog
that had  some surplus relays of similar specs for $2.00each. I bought 6
(they
were subsequently stolen along with my van but that's another story).  I
burned
up one of those before putting in a fuse in line between the relay and the
field.  now I just blow fuses but all the time.  On the E12 the varistor
($4
from Bill) is behind the lower panel cover jumping the field wires in the
connector.  I replaced it.  A friend of mine thought putting in a diode to
block the electrical surge of the collasping field when the motor changes
direction would help.  It didn't.  I suspect in my case something else is
amiss
but I haven't found it yet.  good luck with yours!

dave
E12S in Seattle


> - Yep, the schematic shows one. I'm not sure offhand where it is located,
> but I imagine it's on the reverse relay or on a small card nearby.
>
> Also  the E12S, E15 manual (Elec-Trak.Org) has reverse relay
troubleshooting
> and a service bulletin at the very end.
>
>
> >
> > There might be a varistor that goes across the relay to absorb the
> > sparks, or a capacitor. If so I'd bet it's blown.
> >
>
>
>
>