60 Hz and 50 Hz Generators

L

Thread Starter

Lloyd Throop

My name is Lloyd Throop, and I am a Marine currently stationed in Iraq. We are having some generator issues, and I was looking for help because by no means am I an electrician. We have these things, they are called Expeditionary Vans that we can load up and take anywhere is the world, and work out of them. They need external generator power to run what electrinics are on the inside. We had 60 Hz generators hooked us to it, and everything ran fine, and now that we got new 50 Hz generators, not everything is the van is working.

The van has little signs in it beside the fuse box that say it is a 60 Hz system, and the placards on the generators say 50 Hz. I am just trying to figure out if this could be my problem, or is there something else wrong here. Like I said, some of the stuff in the van would have power, and other things wouldn't. It would also trip some of the fuses on the panel, but they are not marked, so we couldn't find out what they were. If anyone could help me with this matter, I just need to know if a bone stock, no tuning has been done to it, 50 Hz generator could run a 60 Hz system without any problems. Thank you for your time.
 
Lloyd, most 60hz systems will not run on 50hz frequency due to the fact they were not designed to run at the lower frequency. Some things will run for a while (some motors for instance) but due to the lower frequency they will draw more current than designed, typically get hot, hopefully just trip a circuit breaker, and lastly overheat and fail if they continue to run. About the only things that don't care much about low frequency are incandecent light bulbs, they will burn slightly dimmer at lower frequency, but that's about it. Most computers or other devices with power supplies will not work on 50hz, and most have built in protection to shut down, on low frequency.

Basically you need a 60hz generator to run your systems properly. In a real bind I am sure someone could find a way to change the governor speed of the generator, and boost its speed to raise frequency up to 60hz, but hopefully you are not in this kind of bind! I hope this helps.
 
Yes, there can be problems trying to run 60 Hz equipment on 50 Hz power, and visa versa. You can even damage some equipment doing this. On the other hand, some equipment will run fine on either frequency. In that case though, it often explicitly says 50/60 Hz on the name plate.

You need to have someone go over the equipment in detail to determine whether it will run safely on 50 Hz. It's not something that anyone can give a blanket answer to.

However, if you are blowing fuses I would suspect that some of the loads are not compatible with 50 Hz. An AC system is different from a DC system in that the impedance (the AC equivalent to resistance in a DC circuit) varies with the frequency. At lower frequencies things like transformers can overheat (and burn up) even though the amount of *power* being consumed by the load is the same.

In addition, since you are dealing with motor driven generators there can be additional issues. The voltage and frequency output of the generator may not be stable enough for the electronic loads.

So, the short answer is that yes, this can be a problem, and someone who is knowledgeable in the field and who has access to all the drawings and specifications needs to have a look at it. In the mean time, you might damage some of the equipment, and the damage may not be immediately apparent.
 
Lloyd,

The frequency output of a typical generator is directly related to its running speed. For example, a 2 pole generator running at 3600 rpm will produce 60 Hz. If you were able to run the same generator at 3000 rpm it would produce 50 Hz. This is easier said than done.

If you're inclined to tinker, you may be able to improvise and run your 50 Hz generators at the 60 Hz speed, but this might "let the smoke out of it" as we say. It is designed to regulate itself at the 50 Hz speed (lets assume it spins at 3000 rpm) so it would be challenging to get it to run at 3600 rpm. It may do it, but it may not handle that big of an increase in speed for very long and it would be difficult to keep it regulating itself at that speed. (Speed regulation is very important for maintaining frequency.)

Your best bet is to give it away to the Iraqis and get a 60 Hz machine.
 
Tinkering with the governor will not only vary output frequency, but also terminal voltage. By increasing generator speed, the output frequency might match the name-plate frequency but terminal voltage will definitely rise above rated output volts and this is trouble!

For eg, say a 50Hz generator is rated at 400V. Now if the governor setting is varied such that speed and hence frequency would increase to 60Hz. But now the terminal voltage would become greater than 400V, as output generator volts is directly proportional to rotor speed in r.p.m. Speed increases___output frequency increases___ hence output voltage also increases. Plz do keep this in mind.

Best regards,
Shahvir
 
Well, that is exactly how practical generators work! As soon as speed is raised/lowered to correct frequency deviations, the on board AVR (Automatic Voltage Regulator) unit comes into action and adjusts the terminal(hence grid) voltage of the generator in question.

Regards,
Shahvir
 
P

Panagotis John Malaspinas

hi lioyd,

the problem your having is not something you could rectify very quickly. the reason for this is we go by 60hz standard in USA the country you are in and most of Europa and middle east use 50hz stranded that means equipment will not work as they should because of
design. i suggest you get another 60Hz generator shipped to you from states. thanks for your service
 
quick fix if you can.

separate the systems into those that don't care about frequency and those that do.
get hold of a inverter, and some batteries and a regulator.

use the generator to charge the battery (via a regulator), then run the equipment off the inverter (note over size the inverter as some equipment draw more current at start up)
------------
system one/two
generator (50HZ) >> equipment that runs off 50 / 60 HZ
system two/two
generator (50HZ) >> regulator >> DC Volts (battery) >> inverter (60HZ) >> equipment (60HZ)

depending on loads, can also use solar-cells to charge the batteries.

if all else fails go home and have a beer..
 
J

Jim ( Master Electrician)

If you can adjust the govenor on the machine you can bring it up to 60 Hz. This will not affect the voltage output. The voltage is controlled by the armature field excitation current applied to the machine.

You will need to increase the RPM by 20%. Hope this helps. it is likely running at 1500 RPM so the generator rpm will need to increase by 300 RPM to 1800 RPM. This is an example for a 4 pole generator. Whether the machine is 6 pole or 8 pole the 20% speed increase holds. Formula is Frequency = #of pairs of poles X RPM / 60
60 is a constant (rpm per minute)
 
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