Log of SV Free Spirit and ships company

The chronicles of the schooner Free Spirit and her crew, embarking on an open ended journey upon the great rolling heap. Free Spirit is currently pursuing humanitarian and commercial goals in the Dominican Republic, on the island of Hispaniola. Working under the Ocean Reach USA and Paradigm Research banners, she is serving as logistics headquarters, workshop, and development laboratory for many ongoing projects. This is the log of her journey.....

Google
 
Web sailfreespirit.blogspot.com
If you are joining us for the first time, click here for an introduction!
Books and more, at the Schooner Free Spirit Chandelry
Clothes and more, at the Free Spirit Logo Shop!

Saturday, June 19, 2010

Transformers....

Well, here is a techy bit.....We've been having suboptimal performance form our "smart" switchmode battery charger for some time now, so I've finally decided to take matters into my own hands.

The parts....about $150 USD. Notice the 12" tiles for scale.


Fortunately, in the DR, transformer and motor winding is not a black art and is a common streetside profession, so I have been able to gather the needed knowledge and materials easily.

Winding the 5ga solid secondaries was hard work, and assembling the hundreds of core laminates by hand was tedious, but....

We wound the transfomer and, lo and behold, it works! next comes high amperage testing and incorporating control circuitry.

4 hours later...
Tech Stuff:

3.6KVA

Dual 14ga Primaries:
110v and 80-154v , step 10v for universal voltage 80 - 154 and 190 - 264 v operation

Secondaries are 120+A rated 5ga
2 ea 16v and 2 ea 2v, for 16,18,22v (200A) and 32,36,40v (100A) configurations.

Assuming normal or low input voltages, swithcing the primary to higher voltage windings gives 4+ 1.2v downward output steps and one 1.2v upward (more steps with a reduced duty cycle) output step.

This gives a fine grained range of 11 - 23v at 200A in approx 1v increments and 27-41v at 100A.

To this manual (switch based) control, I will be adding an triac circuit to give fine grained voltage and current limit control.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home

Introducing Propcalc 4.0

Use Propcalc to easily match your hull with your engine, transmission, and propeller
Put the known data in the top fields, then hit the Update button to get the answers.
Results, of course, should be verified by a Naval Architect or qualified surveyor.
Data is provided for three bladed propellers of average type
For two or four bladed props, use the modifiers shown below.

Fill out the fields as follows:

Vessel LWL (ft) = Waterline length
Vessel Disp (lbs) = Vessel displacement
(max) HP = Rated Engine Max HP
Engine RPM max = Engine RPM at Max HP
Engine RPM cruise = Desired or estimated cruise rpm
(Cruise or Max) Kts = Speed to work the calculations for
Slip = Propeller efficience. 45% is average for a displacement cruiser.
Gear ratio = 1: Gear ratio of transmission
SL Ratio Adj. = This value will be added (or subtracted, if a negative value) to the calculated S/L ratio.

Key information:

If the "hp required" is greater than the "cruse HP", you have your cruise RPM set too low for your engine parameters.
If the "hp required" is significantly less than the "cruse HP", you have your cruise RPM set too high for your engine parameters.
If the "hp required" is greater than the "Max HP", then your target speed is too high for your engine/hull parameters.
The S/L ratio is calculated automaticaly based on your input. It can be adjusted if necessary, but normally it should be left alone.
If the calculated S/L ratio exceeds S/L MAX, then the results are likely to be non-predictive. Try a lower speed requirement.
SL Ratios of 1.1 - 1.4 are typical of displacement hulls. Semiplaning or planing hulls can go higher.

Typical propeller slip values:

Sailing auxiliary, barges, etc less than 9 Kts............45%
Heavy powerboats, workboats 9 - 15 Kts....................26%
Powerboats, Lightweight Cruisers 15 - 30 Kts..............24%
High speed planing boats 30 - 45 Kts......................20%
V bottom race boats 45 - 90 Kts...........................10%


Note:

it is possible to get irrational answers by irrational input , I.E specifying excessive speed for hull type and length
Any attempt to exceed hull speed (1.34 times the square root of the waterline length in feet) with a displacement hull are likely
to fail unless the hull is extremely fine (multihull) or otherwise exceptional. In such cases, an S/L adjustment would be in order.

2 and 4 bladed props:


For two bladed propellers, multiply the diameter by 1.05, and the pitch by 1.01
For four bladed propellers, multiply the diameter by .94, and the pitch by .98


PROPCALC
  Inputs:
Vessel LWL (ft) =
Vessel Disp (lbs) =
  (max) HP =
  Engine RPM max =
  Engine RPM cruise =
  (Cruise or Max) Kts =
  Slip =
  Gear ratio = 1:
  SL Ratio Adj. =
   
    Solutions:
  Prop rpm max =
  Prop rpm cruise =
  Pitch =
  Diameter =
  Static Thrust =
  Cruise HP =
  Cruise HP% =
  SL Ratio =
  DL Ratio =
  SL Max =
  HP Required =