50Hz VS 60Hz

[StianM]

I was asked by someone about PMS systems and how many generators it can suport. The person asking knew someone that wanted to build a fishingboat with dieselelectrical propulsion.

They had to chose between 50Hz scania generator sets and 60Hz Catapilar generator sets. I recomended the 50Hz since lower speed on engines will reduce the noice and reduced frequensy means lower reacitive power and therfore also reduce the fuel consumption + all consumer electronics here is 50Hz so they don't nead to order special washingmachines and so on.

Later I started thinking what would actually be the best? with increased frequency the transformers nead less iron to do the same task and you would nead bigger diesels to give the same power so a 50Hz boat would be a bit heavier. Would the increased weight and weted surface defend the choice of 50Hz?

[lazeyjack]

stian , hello
go 50, here is why
50 is all over the world except , 2 places:)), when a 60 cycle, system tries to plug in to shore power, whoops@@ frequency converters cost tens of thousands for bigger systems I built my last, 110vac, 60 Hz, became a real pain down here, build for USA market but was sold here, a real bother it is when travelling

[StianM]

stian , hello
go 50, here is why
50 is all over the world except , 2 places:)), when a 60 cycle, system tries to plug in to shore power, whoops@@ frequency converters cost tens of thousands for bigger systems I built my last, 110vac, 60 Hz, became a real pain down here, build for USA market but was sold here, a real bother it is when travelling

I was going to give you some reputation for this one since I did not even think about it, but seams like you where the last one I handed some so I have to spread some around be four giving again.

Unlike you fishing boats are going to stay out fishing 11mounths of the year and don't stay in the port on a shore connection enjoying the local night life:D

[JRM]

The international standard for commercial marine shipping is 60Hz

If your boat is big enough and you will buy normal commercial marine products, you will find that most of this equipment is 60Hz.

I have worked for UK based shipowners and when building new ships we specify 60Hz onboard, even though the UK domestic system is 50Hz.

All the Norwegian yards and equipment suppliers building supply boats will deliver 60Hz ships. I imagine that the Norwegian yards (Aker, Westcon, Simek etc) delivering large fishing vessels (tralers and snurpers) also specify 60Hz.

However, if the boat you are talking of is small enough to use "domestic" appliances, then I can see why you might be tempted to go for 50Hz.

I do not believe that the difference between 50Hz and 60Hz electrical equipment can be seen in the weight and wetted surface of the hull required for each of the options.

I am sure you will do so, but you should also check the voltage.
- European shipyard standard equipment supplying at 450V (consumers are nominal 440V), 60Hz
- some European onshore voltages - 415V and 50Hz
- these are not compatible because the ship voltage is too high for the "domestic" equipment, unless a big voltage drop is engineering into the system

Where the health of your equipment is concerned, an incompatiblility in voltage can be more of a problem than the difference in frequency. I have shore based welding equipment burn out in very short time when people try to use onboard ship.

[StianM]

690VAC 50Hz buildt at aker yards in Norway.
Traficing in Norwegian waters.

http://www.bergenships.com/SHIP/Bergensfjord.jpg

[JRM]

I am not saying that the Norwegian yards cannot build 50Hz ships. Of course they can.

However a sample of the specifications I have from Norwegian yards shows 5 out of 6 having 60Hz systems.

One of the reasons is that the VOLTAGES are linked to the frequency - this is especially important for large vessels generating at 6.6kV or more (medium voltage), and having several different voltages operating onboard. Maybe less important for the vessels generating at 690V (low voltage).

For the same makeup of the magnetic cores, the 50Hz voltages will be 17% lower than with a 60Hz system. The aim is to maintain standard volts per Hertz to get the same flux density.

On a 50Hz system the 240V voltage will be the SAME as on a 60Hz system. But the next voltage up willl be 380V and not 460V.

The number of generators that a power management system (PMS) can support is rather large. Some drilling vessels have 6 or 8 generators working under the same power management system with load dependent start and stop of the generators. Plenty of companies in Norway with experience of these systems.

[StianM]

One of the reasons is that the VOLTAGES are linked to the frequency - this is especially important for large vessels generating at 6.6kV or more (medium voltage), and having several different voltages operating onboard. Maybe less important for the vessels generating at 690V (low voltage).


we have delivered 690 both in 50Hz and in 60Hz and it can be done with the same generator. Only have to adjust the exitation in the AVR.

[CDK]

Of course you can adjust the output regardless of the frequency. Only the old-fashioned ones with a phase shift capacitor bank cannot be adjusted.
On a ship, I'd go for 50 Hz. anyway. Should it accidentally be connected to a 60 Hz source there will be no smoke, at least not immediately.