Re: (ET) Need a lot of detalied how info

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

R4, R5, R6 & R7 are 10 and 20 ohm 10Watt (I think) Ceramic resistors.
If a resistor opens you loose your shunt field and current in the armature
goes up significantly.
A better design would use FW resistors in parallel with the field so if a
resistor
opened the motor would just slow down.  The draw back of this is a larger
wattage
resistor is required as you increase FW.
All 4 of these resistors are mounted on a 3.5 by 4" PCB on my E15.  This is
attached to the
main circuit board with two screws that go through a right angle bracket.
The slow speed armature resistors are large nichrome strips wrapped around
a ceramic element
up front by the charger.
Rod



                                                                           
                                        
                      Ken Olum                                             
                                        
                      <kdo cosmos phy tufts edu        To:       elec-trak 
cosmos phy tufts edu                    
                      >                                cc:                 
                                        
                      Sent by:                         Subject:  Re: (ET) 
Need a lot of detalied how info          
                      owner-elec-trak cosmos ph                            
                                        
                      y.tufts.edu                                          
                                        
                                                                           
                                        
                                                                           
                                        
                      04/23/03 04:18 PM                                    
                                        
                                                                           
                                        
                                                                           
                                        




   From: Paul and Sue Abendroth <pabendro gemair com>
   Date: Mon, 21 Apr 2003 23:17:40 -0400

   At 09:34 PM 4/21/03 , Roy Vanderhoef wrote:
   >The first problem is for some reason the ET started pegging the usage
   >meter in the upper speed ranges.  All is fine in the first couple
   >ranges.  If I remember correctly it was some sort of resistor bank or
   >something like that that you guy/gals said was most likely the problem.
   >So where do I start, What do I check, where is it located, and how do I
   >test it, and replace it.  Where do I get the replacement parts. Etc

   Most likely are the 2 resistors - the flat silver colored strips ahead
of
   the battery charger, mounted to the bracket the timer is on. When they
   fail, you can usually see the break. The posts they are mounted to may
be
   loose. The switches are the last micro-switches on the throttle control,

   but less likely to be the problem.

That doesn't seem right.  I thought the metallic resistors were the
ones that decrease the armature current and are invoked in the low
speeds.  The field weakening resistors, which would cause the current
problem if open, are on some other card.

                              Ken