[modeleng] Electric Traction Problems
- From: "psbr20252@xxxxxxxxxxxxxxxx" <psbr20252@xxxxxxxxxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Thu, 5 Apr 2007 07:10:00 -0400
Over the Spring Lambing weekend at the LM&WR (where we gave over 1200
rides!) I had the opportunity to try Topsy (a petrol electric) in anger=2E=
Topsy has two 12v car batteries wired in series driving through a 4QD Uni-=
8
(max 135A) controller a series wound forklift traction motor=2E The
batteries are kept charged by a 24v alternator driven from a 5HP honda
engine=2E
When solo, Topsy was very lively, in traffic (two coaches) Topsy was a wus=
s
and couldn't pull the skin off a rice pudding!
My initial concern was that the motor was shot (it was about 7 years old
and I had rescued it from a scrapyard)=2E So last weekend I tried the
ultimate in "bang-bang" control=2E Two jump leads from the battery direct=
to
the Forward/Reverse contactor=2E There was no lack of power there! Topsy=
hauled a petrol hydraulic (dead) three coaches and three adults with no
problem around the track=2E
I contacted 4QD (and unlike most people) I found him rather unhelpful! I
was told to use the calculator (which is fine if you are designing, but
little use if the locomotive exists) or that Topsy was too heavy, the
gearing was wrong or that gradients were too steep=2E He wouldn't respond=
to
my question of whether the Uni-8 was not able to deliver the stated curent=
(or how it delivered it)=2E
Now I reckon Topsy weighs approximately 300kg, the motor rating plate
(admittedly in German) says 24v and 90A (now as this is series wound I
assume this means stall current=2E)
One item of interest is that the 4QD controller comes with 4mm sq wire
(smaller than a cooker cable) yet the contactor (that came with the motor)=
has multistrand copper with the thickness of expensive car jump leads!
Now I am loathe to pay out for a bigger controller (the biggest one from
4QD is =A3245!) So I have a couple of options - (1) Use the batteries as 1=
2v
then 24v=2E Possibly a bit jerky, but the cheapest option, or (2) Use a
carbon pile regulator=2E The latter I have seen once in practice, but can=
find little information out on the web=2E
So, firstly, any thoughts as to why I am having problems with the
controller (is it current limiting, is being series wound affecting its
control=3F) and does anybody have any design information on carbon pile
regulators=2E
Cheers
Peter
=20
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