At 11:40 AM 8/08/2010, Pitt wrote:
><snip> Honestly I would rather not bother with batteries and have a
>diesel/electric propulsion and really only sail with an emergency
>propulsion. I am starting to see the talk about honda generators
>being dodgy wired direct to the drive motor, am I correct this can be done?
>
>I have a diesel / air cooled generator. PowR-Quip PQDE 6500 ( see
>photo diesel generator ) Would I be dreaming to hope that a air
>blower would be capable of cooling the generator down in the
>lazzeret and using this generator to run the electric drive motor
>direct. Then keeping the old house bank as it is, charging with
>solar and from the generator when needed I keep being turned off the
>project with almost everybody telling me the boat is too big and it
>would take too many batteries. A new marine generator is too far
>out of budget and I already have this one.
>Some advice on electric motors would be welcome also,
G'day Pitt, All
Sail with emergency propulsion? Right, to me that means you do not
want to count on the diesel generator for propulsion, so you want
(need) batteries in the loop. You will need a charger from the diesel
for the house bank anyway, so get a(some) big(ger) one(/s), and use
the house bank for your power source for your propulsion.
How much power are you looking for? Without knowing what your house
bank is (12V or 24V and amp-hour capacity) I can offer a few options.
You can get motor controllers such as the Curtis 1205 that are 12V,
400A peak, (175A 1 hour rating) so 4800 watt (4.8kW) peak, 2.1kW 1
hour. That's probably a bit low for your boat. 24V systems double the
power, (same amps at twice the volts = twice the power). If 9.6kW
peak and 4.2kW continuous is enough then you can do it at 24V. If
your house battery is 12V, but you are looking at needing 24V, you
could set up a second, identical, 12V bank in you freed-up space,
doubling your normal house capacity in non-propulsion times, and the
"extra" bank being switched in series with your existing house bank
for propulsion times (drawing power from and recharging both banks evenly).
Adding large chargers (100A+ size) to each section would allow
series-hybrid propulsion continuously at whatever the continuous
capacity of the chargers allows. Not particularly efficient, but if
it is "now and then" needed, not a big issue.
If your house battery is a bit small for this, you could add three
identical banks, and use a contactor-switching setup to control the
motor directly from battery switched power, with no other controller.
This only gives three steps (12V/24V/48V) but may prove to be all you need.
=====
Next is driving a motor direct from the generator. Your generator
will be probably either 110VAC/60Hz or 220/240VAC 50Hz (depending on
where in the world you come from, that seems to be the most common
alternatives, but yours may be something else). If you want to run a
motor direct from the genny, this is an issue. Your choices for
direct connect really comes down (depending on your skills and knowlwge) to:
1) Direct drive an AC motor, and use a mechanical/hydraulic speed
control for speed control. Depending on your circumstances (your
skills and available materials), this may be an acceptable way for
you. It will not be particularly efficient, but if you have hydraulic
skills you may be able to use a hydraulic drive off the diesel engine
(without the extra efficiency lossed in convering to electrical
energy and bac to mechanical again). I wouldn't, as you are likely to
loose a big efficiency hit, but I'm not a hydraulics person. Variable
pulley or Reeves (type) drive may be an option, as well as as the
option of an automotive gearbox (limited ratios and issues with speed changes).
2) Using a high-voltage (90V or 180V) DC motor and a DC speed control
such as those made by KB electronics - most of them are phase-angle
control, so the genny will not like them a lot, but if you can find a
PWM version that'd be better. This will give "infinite" speed setting
(0 to max), from a potentiometer, and if you use a 4-quadrant type
controller you get reverse at the twist of the 'pot'. The way these
are made, they are usually a single circuit board, so you are likely
able to get plenty of layers of electronic or motor lacquer onto the
board to keep the moisture away for a time. Keep a spare in a fully
sealed bag so that _when_ the moisture gets in, you can swap them
over. See below for keeping the moisture out of a box.
3) If there is space around the diesel, it would be possible to
connect a pair of three-phase motors, one connected to the diesel,
with a bit of circuitry to make it generate, one for propulsion. As
you change the speed of the diesel, the propulsion one will change
speed the same. If you can find a 2-speed motor (you can get
2-pole/8-pole motors) you can have high-speed/low speed modes, as
well as the rev range of the diesel.
4) You can buy 3-phase speed controls that run from single phase
power. They take single phase in, turn it into high-voltage DC, then
convert it back into psudo-3-phase power to run a 3-phase motor,
usually from 0 to 100% speed, but depending on the selected hardware
you may be able to go to 200% motor speed. The way most of these
drives are made, you have little hope of lacqering the electronics to
keep the oisture out. All is not lost, however, as most put the heat
into a fan-cooled heatsink put the back, and it is possible (I've
done it) to mount a plastic box around the drive, with a hole cut out
the back for the heatsink to stick out through. Sealant around the
hole and silica-gel absorbent in the front will keep the electronics
dry. As the box thermally cycles it will expand and contract the air,
so to prevent it sucking in moist air, add a rubber membrane (I use
10-thou' insertion rubber) to allow it to move without exchanging air.
===
Choice of motor. How damp is your bilge? Electricity and moisture is
always a problem, the lower the voltage, the less of a problem for
tracking out, the more of a problem for bad connections.
How big is your budget? New or used? Since a new marine genny is out
of your budget, I guess the budget is "find a way to get enough
whilst spending as little as possible".
You can buy AC motors that are stainless-steel cased,
pressure-wash-down sealed. If you decide on an AC route, that may be
an option (or may be the decider if your bilges are often wet). Ebay
is your friend.
DC you can use new, but you can get ex-forklift motors. An option
would be a big old 36V or 48V forklift series motor, if its' "too
big" that doesn't matter, it'll use whatever you give it and however
much load your prop puts on it.
Brushless DC you have issues with moisture getting into the sensors
and needs to be sealed very well - this is what you are really paying
for when you get a "marinised" version of an off-the-shelf (golf car
type) brushless DC motor. You are unlikely to get brushless DC used,
unless someone has bought a system and found it to be too small.
===
Hope this helps
Regards
[Technik] James
No comments:
Post a Comment