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]

Originally Posted by 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

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

[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.

[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]

Originally Posted by JRM

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.

[powerabout]

This is an old thread but I just like to mention....
working on an offshore vessel and its 60hz.
We seem to be always buying domestic appliances, washing machines, dryers, dishwashers etc. ( and so do the others vessels in the fleet)
I even checked the electric jug on the bridge, it says 50hz and we seem to be buying them also.

Where do you get 220- 60hz kit from?

( I thought the 220 60 was just to make the Philipinos feel at home?)

[jonr]

Connecting any generator to shore power will cause smoke - or at least a blown breaker - unless you are very careful to get the waveforms synchronized. Generally a bad idea.

[CDK]

Originally Posted by powerabout

This is an old thread but I just like to mention....
working on an offshore vessel and its 60hz.
We seem to be always buying domestic appliances, washing machines, dryers, dishwashers etc. ( and so do the others vessels in the fleet)
I even checked the electric jug on the bridge, it says 50hz and we seem to be buying them also.

Where do you get 220- 60hz kit from?

( I thought the 220 60 was just to make the Philipinos feel at home?)

The frequency is only important when the load is inductive. Water heaters, light bulbs and computers accept both 50 and 60 Hz.

[powerabout]

CDK thats what I would have thought also.
so why does the electric kettle only say 50hz? Is there separate testing so they only do one test?

We have asked our agent to get a new urn for the main galley and we asked for 220 60, he cant find one in Europe and his suppliers say dont plug in a 50 one to 60 ( well the first one lasted 2 years)
I would have thought no prob, an element is just like a light bulb?
Our domestic applicances only say 50 so I guess as they have electric motors in them they are going a bit faster than they should?
So where do you get 220 50 kit?
I wonder what is on board all those commercial vessels with 220/440 60hz?
I have checked with electric motor suppliers before and they say the standard is for 10% over/underspeed so you cannot run a 50 at 60hz

I had never thought of the problem as all the Megayachts I worked on were 220/380 50...sensible power!
( PS computers/battery chargers/inverters these days have switch mode power supplies that why they can do both)

[CDK]

You can run a 50 Hz motor on 60 Hz, but the result may be disappointing. It will try to run faster, but it draws less current, so it has less torque.
No problem for a light load, like a fan, but an A/C compressor may not be able to reach the designed rpm and keeps using the starter winding until it burns out.

Converting 60 to 50 Hz can be done with a solid state inverter if the load is limited to a few Kws.

[powerabout]

CDK
Just curious what happens to 3 phase motors?

[CDK]

1800 rpm instead of 1500, for example, but with approx 20% less power.
For motors without load during start-up (clutch operated loads) I expect no problems, but a pump might not reach the nominal rpm.

There's no harm in trying, the worst that can happen is that the power is insufficient. Engineers like myself tend to first exactly calculate the required motor size, then take the next larger one to be on the safe side, so you may be lucky.