Voyaging gensetsDec 16, 2013
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The generator end
It is the generator end and control systems that really separate one brand from another. These are the parts most manufacturers produce in-house and where the greatest innovation will be found. New trends include digital controls, efficiency improvements in the generator units themselves, voltage stabilization to control voltage spikes and dips and surge controls to help handle high start-up loads typically found in air conditioners and other motors. Other notable improvements can be seen in weight reduction, smaller footprints and greater sound control.
Courtesy Northern Lights
A heavy-duty installation is this 12-kW Northern Lights M843NW2 unit, also with a sound enclosure, installed on an Arcturos 50 power voyager.
The greatest innovations in generator technology have come from the smaller, lighter generators. The desire to reduce weight and size has driven manufacturers such as Fischer Panda and Whisper Power to come up with some interesting improvements. Electrical efficiency drops when temperatures increase and for this reason several manufacturers are opting for water cooling the generator windings. Mase Generators feels this is so important they water cooled their back ends even when using air cooled motors. Other improvements are made by denser packing of the generator windings and using brushless rotors with permanent magnets.
With today’s modern electronics it is critical to maintain steady voltage and frequency in the power supply. This is not a problem when the generator is running with a steady load. It can, however, become an issue when heavy loads such as air conditioning and other devices using electric motors, switch on and off. The momentary start loads can cause frequencies and voltages to drop, sometimes dramatically. Likewise, when a heavy load is shut off the power can briefly surge. These transient spikes and dips can shorten the life of electric motors and possibly damage sensitive electronics. The ability of a generator to respond to these changes is called transient response and becomes of particular importance on small generators.
Frequency is a result of generator rpm and will remain constant under a steady load. The speed the engine is turning is set by a governor on the engine. The problem arises when additional loads are added or removed from the generator. The time it takes the governor to respond to these changes can affect the depth of frequency changes. Typically this should be no more than 3 to 5 percent. With older style mechanical governors the response to loads can be relatively slow. This slow response can cause the engine to momentarily slow down under load and then momentarily over rev as it recovers from the load causing voltage drops and spikes. To combat this problem, electronic governors are sometimes used to react quicker to load changes. The catch is if the response is too fast it could result in the engine stalling. Electronic governors can help keep this critical balance while reducing the depth of the dips and spikes.
Voltage regulation is also an important factor in controlling transient response. Most voltage regulation is closely tied to frequency so that as frequency changes, voltage will change as well. Newer electronic voltage controls can help keep the balance between load and power, helping reduce the effect of changes. This may sometimes result in a slower response and recovery time, but will also help level out the depths of change. Some of these newer voltage regulators can boost the voltage during equipment startups to help smooth out the dips.
Fischer Panda has added a proprietary voltage booster circuitry to their line of small generators to help prevent start up loads from over loading the generator. They claim with this new circuitry their smallest unit can start and run two air conditioning units totaling 28,000 BTU, pretty impressive for a 4.2-kW generator.
A Mas Power 8-kW with sound enclosure installed on an Island Packet 41 SP.
One of the more noticeable changes in new generators is the introduction of digital remote controls. The days of the simple start/stop panels are numbered as most manufacturers switch to using digital panels. Ease of installation and the ability to get error codes in the event of a fault are the primary advantages. Knowing the errors at a glance can be very helpful in trouble shooting any faults and preventing bigger problems.
Several manufacturers are making panels that will interface with NMEA 2000 networks, allowing the controls to be integrated with other onboard systems.
Noise and vibration
Reducing noise and vibration are also on the forefront of manufacturers improvements. The use of water-cooled windings has helped lessen noise by reducing the size of openings required for the greater volume of air needed with air-cooled windings. Manufacturers of air-cooled units have learned to reduce noise with the use of baffles and ducting designed to block sound waves. Sound enclosures have improved with denser insulation and better construction.
Another major source of noise is from vibration transmitted to the vessel. This is particularly true with newer lighter vessels such as catamarans. New softer mounts are helping reduce this by absorbing vibrations. Improvements have also been made in how exhaust gases are handled. In an effort to reduce exhaust back pressure and improve overall efficiency most manufacturers recommend the use of gas/water separators in the exhaust system. This has the added effect of reducing exhaust noise.
The future holds some interesting new products for power generation. Some companies are working on DC hybrid systems, which will produce DC power for a battery bank that in turn will use inverters to supply AC power. Like hybrid cars, these units will automatically start and come online when there is a larger power demand and shut off when the power use is low. This type of system has several advantages over the conventional AC generators. Because the power is “on demand,” the units will not always be running, this will save fuel and wear on the motor. As DC does not need a set frequency the engine can run at any speed. This allows the generator to run at a lower rpm when demand is low and only increase rpm as demand increases. DC systems will integrate well with solar panels and wind generators as well, further reducing operating costs. DC generators can be used with electric propulsion, allowing the vessel to have a single electric generator to supply all the vessel needs. It may be a few years before we start to see systems like this in widespread use, but as technology improves and costs decrease these systems offer an interesting alternative.
Marine generators are slowly evolving as new technologies come online. Water-cooled windings, innovative load-handling circuits, reduced size and weight and better sound-proofing have all helped in making today’s generators a practical option for most modern vessels with greater power demands.
Capt. Wayne Canning lives on his Irwin 40 Vayu, in Wilmington N.C. He is a full-time Marine Surveyor, freelance writer, and consultant/project manager on major repairs. Visit www.4ABetterBoat.com and www.projectboatzen.com for more info.