Mv dirona physics electricity and magnetism study guide


Our decision to go with two alternator is unrelated to our want for two generators. They really are seperate points. We want a second generator because that’s our own source of power when at anchor and, if the generator fails, we have a problem. Our goal is to never redirect or cut short a trip due to mechanical problems so we don’t want a failed generator to stop us. All of us have only a limited lifetime and we don’t want to give up weeks every year on mechanical faults. Because our main engine can produce 9kW, it can serve as a backup generator. But, generator autostart is key. We need to be able to be away from the boat for long periods and know the batteries will not be excessively discharged. Our solution is to put autostart on the main so it can serve as a backup generator:

If we were buying another boat, we would likely spec a second generator but it’s not certain. Since the second gen for us is only to backup the primary gen, using the main to do that seems to work fairly well. Generators are pretty reliable and rarely fail to run. Likely we would go with a second gen but not for sure given how well the backup system we have built seems to work.

Another common driver of two gens is to have a big one to handle oven, dryer, and other big loads and a small one to handle the common case. We use inverters and load shedding to be able to operate big loads without having a big generator. This avoids the problem of having a 20kW that basically is never loaded and allows a single generator to handle the load. So, with backup power if the generator fails and no need for big/little config to support peaks, the push to a second gen is less strong. We only need the second one for redundancy.

The reason we have two alternators is we want to have enough capacity to fully support house loads without running the generator when underway. la gastronomia The argument here is twofold: 1) the main engine has lots of excess capacity when underway, and 2) running the gen 24×7 when underway means you double your oil changes, you have to carry more supplies, it requires more service, etc. It seems nuts to have more than one power source in the common case — you need it for redundancy but, in the common case, we want only a single source so we design to run like this:

1) Shore: we can run off 60hz, 50Hz, 50A, 32A, 16A, and even down to 8A (by using 2). This works so well we never have to run the gen when on shore power. If you spend time at marinas you’ll see larger boats running the gen all the time due to not having enough shore power to support their peak loads. The new power system article describes how this works fairly well: The remaining aspects of the design are covered in the two generators when you only have one article:

The serpentine drive belt on the front of the engine is rated to drive heavy duty equipment so that isn’t a problem. When our boat was delivered by Cascade, they had an 85A start alternator and 190A house alternator. I upgraded to 2x 190A which will take more load from the front of the engine but it’s all well within the design limits of the components involved. electric utility companies in arizona There was no change in the number of pulleys on the engine when upgrading to 2x 190A.

On Dirona, Hydraulic power is proeduced by identical pumps on the Wing and the Main engines each of which is capable of running the system. Underway the stabilizers are run by the main engine, when in close quarters, the thrusters and windlass are run off the wing engine since the main is at idle. But, either engine can run the system so, if the main fails and we run off the wing, we still have stabilizers. And, if the wing fails and we’re only on the main, we still have thrusters and windlass available (but the main needs to be brought up off idle to use them fully).

The design you describe of running the hydraulics off of a 3 PH motor that is is fed by the generator through a VFD is used on ABT STAR (Stabilization At Rest) so it certainly works. In all the examples we’ve seen the main engine still has a hydraulic pump PTO so the hydraulics can be run directly when it’s running. I can’t think of any reason why you couldn’t run through the electric motor all the time — it’s a continuous rated system. The only downside is the rather large loss of efficiency when converting rotating energy to electricity and then converting that to hydraulic power. Direct drive is considerably more efficient.

On most Nordhanv’s the crane is hydraulic and driven off a hydraulic power pack rather than the boats hydraulic system. This is a simple design but does suffer the inefficiencies of multiple conversions. Since it’s only used for short periods, it’s simplicity wins over efficiency and the double conversion system works fine. An alternative I looked at was using the boat hydraulic system to drive the crane but they aren’t that easy to interface and my conclusion was the hassle wasn’t worth the trouble and we use the standard electric power pack to drive the crane.

Yes, we absolutely did consider a twin engine configuration. I larger boats, I would definitely select two engines. But, as the boat sizes drops down below 60′, single engine designs seem to win out for us. In smaller boats, the additional space that twin engines require reduce the fuel load that can be carried and shorten the boat’s overall range. In larger boats there is plenty of room for fuel but in smaller boats, the additional space required for twin engines reduce the boats range below what we want. Twin engines are just a small amount less efficient than singles as well so, for our usage, in boats less than 60′ single engines seem to be a better choice with longer range. If were to go with a larger boat, it’s highly likely we would go with 2 symmetric engines. I particularly like the application of two John Deere 4045AFM85 in many newer Nordhavn 60s. The 4045AFM85 is the Tier III emissions, 4 cylinder variant of our Deere 6068 that has served us so well over the last 10,000 hours.

You asked “after 10000 hours on one engine, why would you go for two?” We put 4,100 hours on the twin Cummins in our previous boat without issue and 10,100 hours on the single Deere in this boat also without issue. So your question could be “with 18,300 hours having never seen a failure, why deploy more than a single engine?” I agree with you that diesel engine failures are rare but they do happen. electricity questions and answers pdf We have all seen an over-the-highway truck at the side of the highway. Diesel engine mechanics continue to earn excellent livings even though their patients are well built and last long. I really like redundancy.

We really do want to have two engines capable of moving the boat but we could have gone for two symmetric engines or a main and a wing. e electricity bill Due to space limitations and range considerations, we went with a main and a wing and we’re quite happy with the overall configuration. If we bought another under 60′ boat, we would make the same choice next time. If we bought a larger boat where two symmetric engines could be installed without giving up range, we would probably do it and you asked why we would go with twins.

For redundancy reasons, we have already decided we are going with two engines so the only question left is should they be the same (twins) or asymmetric (main with a wing). If we ignore space, range, and efficiency considerations, the advantage of twins is the backup engine is actually running rather than waiting to be started. The second engine in a twin engine configuration has 1/2 the horsepower and, running at higher than normal load can continue to run the boat at normal or very nearly normal speeds. If we drop back to our wing engine, we’re down to 40 hp engine with a continuous rating that is probably closer to 25hp. It works well, it will move the boat at over 4 kts, it’s safe, but it would be far from ideal in heavy seas.

There are lots of arguments for and against asymmetric power configurations. We selected an asymmetric design on Dirona for space, efficiency, and range gains. I’ve also seen it used by ice breakers and military boats to allow massive power to be applied when needed and then to fall back to efficient operation when the extra power isn’t required.

That’s a good point Eric. A day tank doesn’t really work very well for us unless it’s upwards of 60 to 80 gallons and we do like having a day tank and using it like a day tank with explicit transfers to the tank through filtration. So with twins, we would either need to give up the extra security of the wing fuel tank or need space for two at least medium sized day tanks. Some recent builds on the larger Nordhavn’s have elected to delete the wing tank entirely on the argument that fuel problems are very unlikely on boats that run a full day tank protocol and only transfer fuel to the day tank through filters.

From my perspective, it’s a perfectly reasonable option to give up the wing tank and run both engines on the same day tank. The wing tank does provide some additional security but, with a good sized day tank for the rest of the boat, the probability of problems that would have been avoided with a separate wing tank are fairly small. I probably would be comfortable with the single day tank layout if going to twins.

Thanks for the feedback Julie. We used Nobeltec for more than a decade and generally liked it. Our only big complaints with Nobeltec where it does crash occasionally and, when it does, it usually looses most of the recent track. Annoying but not debilitating. When making the decision between all the options open back in 2010, we elected to go with TimeZero mostly because it can share chart data at no extra charge with Furuno NN3D and supports integration with Furuno including RADAR overlay. The ability to share chart data with Furuno means that you can buy charts once and have them available redundantly on two different systems on the boat. This gives us the redundancy we want without forcing us to pay double for chart data. When you cruising large parts of the world, chart data costs can be material.

Had we not chosen TimeZero, we likely would have stuck with Nobeltec. With the subsequent acquisition of Nobeltec, the choice wouldn’t have mattered and we would ended up on TimeZero no matter what. Overall TimeZero is more stable than Nobeltec and the largest weaknesses of TimeZero have been addressed since the acquisition of Nobeltec and we find the newest version to be quite good.

At a distance, this sounds like a wonderful idea and I know it has been used in commercial applications in the past. However, modern high pressure common rail engines have very low tolerance to fuel problems, emission standards won’t allow it, and modern oils are very carefully designed with special additives to prevent burning (they are getting better and better at making high quality lubricants that burn very poorly). Engine oil recycling is a more environmentally sensitive approach and most manufacturers including Deere don’t permit burning used crankcase oil.

The approach we take is to have 5 pails of 4 gallons (20 liters) with 4 full of clean oil and one empty. We can pump into the empty one and fill from one of the full containers. This allows us to do 3 main engine oil changes and 2 generator changes while out and when we return to shore, we need to pour off the used oil, discard the pails, and buy new ones. gas number It ends up being a fairly simple approach and allows us to operate with less chance of fuel system problems.

Good question and I will eventually loop back with the full story of what works and what doesn’t and what I’ve learned over the years. The quick answer on this one is “unsuccessful” — so far I’ve tried just the ultrasonic sensor (there were no focus tubes available at that point), the first generation focus tube, and this enclosed full length focus tube. I’m a bit surprised in that the latest full length, fully enclosed focused tube looks like a very nice solution. It’s better than anything I’ve tried so far but it’s still not a reliable solution. It probably works 60% of the time. What I plan to try next is a completely different system that has been getting good reports. On my next trip back to the US, I’ll be getting: 1) Maretron Submersible Pressure Transducer 0 to 1.5 PSI (PTS-0-1.5PSI-01), and 2) Maretron FPM100. I use pressure sensing for the fuel measurement and I’m super impressed with the accuracy so I know this will work well. What I don’t know is what life expectancy the pressure sensor will have. I’ll report back but I’m optimistic that this one will deliver the stable, reliable results for which I’ve been looking.

James, I was thinking about this and in oil water separators which see turbid water with foaming which can cause issues with ultrasonic sensors, we use continuous read analog level sensors. We buy from a company FPI and you can get both 4-20ma and 0-10 VDC options. You can specify the materials of the tube and float and length span, etc. The only issue I can see if interference between the tube and float over time but just use a M12 connector and pull it out monthly or so. I have used pressure transmitters as you said but the issue here is you must have access to the bottom of the tank and the orifice can become clogged. While you could use a gauge protector you risk accuracy although you could span it yourself. I would use a dwyer 628 with M12 connector once again. About $80 and they last forever. electricity lesson plans for 5th grade I also thought that technically the density of the grey and black water could vary depending upon usage, etc. Overall I think the float I mentioned above is perfect. What input does the Maretron accept?