[Milsurplus] Re: 1-2 F caps

[WA5CAB at cs.com]

There are basically three ways to build DC motors (which includes the motor 
side of all dynamotors and inverters).  Series, shunt and compound.  The 
description refers to where the field winding(s) is electrically connected relative 
to the armature.  Small dynamotors are shunt wound, meaning that the field 
windings are in parallel with the armature.  Automobile starter motors are series 
wound.  I don't know of any dynamotors that are series wound.  Larger 
dynamotors and inverters may be compound wound, meaning that part of the field 
windings are in series with and part in parallel with the armature.

Typical 1/2 second starting current for a shunt wound dynamotor is 3X the 
rated full load amps.  For a compound wound unit, figure 5X.  This assumes good 
bearings and initial temperature above 32 F.

So in hard numbers, to start a DY-17A/ART-13,  you need a supply that can 
source about 100 amps for 1/2 second.  The PE-73 needs about 60 amps.  The BD-77 
needs 120 amps.  The DM-33 or DY-8 needs 21 amps.  50% greater capability 
won't hurt anything.  I use a PP-1104/G (two actually).  Although I co-authored an 
ER article some years back on how to do it, I wouldn't personally use a 
consumer grade supply that lacked the surge capacity to start whatever load I 
wanted to run.

TANSTAAFL.

In a message dated 10/24/2007 10:50:29 PM Central Daylight Time, 
brooke at pacific.net writes: 
> You might consider Ni-MH SubC cells.  I've been talking to vendors about 
> getting packs made for my new 5590BA battery adapter.
> http://www.prc68.com/P/5590BAv2.html
> 
> They are testing them at 30 Amps load for racing RC cars.
> 1.2 V run down and about 1.4 volts freshly charged/cell.
> Not sure how much current you need to start a dynamo?
> 
> You probably could use smaller cells depending on how much energy you need 
> to 
> get up to speed.

Robert & Susan Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at comcast.net> (Backup email)
   
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