Hz question

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Onsite_energy

Onsite_energy

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Just looking for other opinion, most gensets they have a governor that keeps that at 59.9-60.3 hz I have a kobota 12kw,100/50 120/240 under a light load it runs 63 hz 130v but under full load it's at 60.1 on the button.... It has no governor but in the fuel pump so in guessing that's why it's over run?? Will it hurt anything to leave it at 63 cycles 130/260v??


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Answer is really more dependent on equipment sensitivity that is being supplied.

Resistance type loads won't matter at all. Most inductive loads will not be effected much either by 2 or 3 Hz. A lot of electronics are rectified to DC so the frequency don't matter much either when looking at basics of power supply to them. Anything that references input frequency for timing or something like that will not be as consistent as it is on utility power which almost never varies by more then a tenth of a cycle. I think you are not seeing much equipment that references input frequency for such purposes anymore though.
 
kwired said:
Answer is really more dependent on equipment sensitivity that is being supplied.

Resistance type loads won't matter at all. Most inductive loads will not be effected much either by 2 or 3 Hz. A lot of electronics are rectified to DC so the frequency don't matter much either when looking at basics of power supply to them. Anything that references input frequency for timing or something like that will not be as consistent as it is on utility power which almost never varies by more then a tenth of a cycle. I think you are not seeing much equipment that references input frequency for such purposes anymore though.
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Those that I've seen that do typically reference 63Hz as the maximum.
 
Thanks for the input!! I forget that most everything is knocked down to 9-28vdc anymore .... Good for the gensets I guess ,it does say on the tag 1800rpm min I just don't see small ones like this often but now that I think of it a few gas engines were at 63hz with no load bank and dropped about the same 60.1 loaded using internal governors like this one thanks again!! A refresher never hurts


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Onsite_energy said:
Just looking for other opinion, most gensets they have a governor that keeps that at 59.9-60.3 hz I have a kobota 12kw,100/50 120/240 under a light load it runs 63 hz 130v but under full load it's at 60.1 on the button.... It has no governor but in the fuel pump so in guessing that's why it's over run?? Will it hurt anything to leave it at 63 cycles 130/260v??
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I would be more concerned about 130v with e!ectronics that don't provide a great deal of load which would cause he voltage to drop. Some electronic may not take to kindly to seeing 130v. The frequency I would be less concerned about because with electronic items they use an AC to DC power supplys and actually operate on DC.
The frequency would only come into place with something that syncs with the frequency such as a clock. An induction motor's speed is also based of the frequency an will run slightly fast but in most cases the would be of no consequence anyway.
 
It has a rheostat that lets you lower the voltage 130v is what's coming out of the unit and 63 cycles, I guess my real question would be does it hurt the unit to over run 60hz? Sorry about the mass confusion lol


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Onsite_energy said:
Just looking for other opinion, most gensets they have a governor that keeps that at 59.9-60.3 hz I have a kobota 12kw,100/50 120/240 under a light load it runs 63 hz 130v but under full load it's at 60.1 on the button.... It has no governor but in the fuel pump so in guessing that's why it's over run?? Will it hurt anything to leave it at 63 cycles 130/260v??
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A frequently asked question.......
 
Haji said:
Much more harmful is under frequency: transformers would burn up, motors would overheat......
So try to keep the frequency variation within 2 cycles.
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What is your sourse?
My application data indicates that a +-5% frequency deviation doesn't severely affect a motor. Induction motors will either run faster or sdlower, with +5% starting tor we ue will be down 10% with -5% frequency starting torque up 10%. There is no significant change in efficiency, PF, FLA, overload capacity, magnetic noise or temperature rise. With +5% the the starting current will be down 5% and with -5% it will be up 5%.
Likewise with transformers. With transformers under frequency will increase the temperature rise but would be insignificant with this small amount of underfrequency. Transformers do well with over frequency though.
However, with a significant over voltage condition the core can saturate as would also happen with motors which results in the current spiking but at +5% this is really insignificant. Motor commonly are designed to operate acceptably at +-10% voltage anyway.
 
Well, my recommendation to keep the frequency variation within 2 cycles is to restrict the combined variation of voltage and frequency within 10%.
 
Genset Frequency vs ATS Sync Operation

Genset Frequency vs ATS Sync Operation

I am in agreement with the comments posted here with regard to smaller single phase gensets. But in a 3-phase commercial or industrial environment with larger units that are connected to automatic transfer switches the situation is quite different. These units typically employ in-phase monitors (sync check relays) that only allow load transfer when the phase angle of the two sources are within certain electrical degrees (usually < 10.) We like to see a difference of 0.2 Hz between sources to get a timely transfer in a hot bus-hot bus scenario. This occurs during retransfer back to normal after a power failure or a test performed from the test switch. Since utility frequencies are pretty much locked on to 60.00Hz, + or - 0.01 Hz, this would put the gen setting to 60.2 Hz. Greater than this value the sweep time becomes too fast (no transfer), less than this, sweep time is too slow and in some cases never reaches the sync window (timeout occurs) and locks out the ATS (mechanical failure fault.)
This condition applies only to 2 position, standard transition ATS units as opposed to 3 position, delayed transition units.
 
Really interesting thread. I have a portable generator that is approximately 5kW. I have it wired as a home source backup power. Once it was all wired in, I ran it with my fluke DMM hooked up to it along with my oscilloscope. The voltage is fine, but the frequency was also at 63Hz. I spoke to the manufacturer about this and they noted the 63Hz is the correct frequency for it to be operating at. Very puzzling. Also, the waveform is pretty choppy and not smooth.
 
mjmike said:
Really interesting thread. I have a portable generator that is approximately 5kW. I have it wired as a home source backup power. Once it was all wired in, I ran it with my fluke DMM hooked up to it along with my oscilloscope. The voltage is fine, but the frequency was also at 63Hz. I spoke to the manufacturer about this and they noted the 63Hz is the correct frequency for it to be operating at. Very puzzling. Also, the waveform is pretty choppy and not smooth.
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The choppy waveform may relate mainly to the physical shape and orientation of the coils and the shape of the magnetic field. Or is may have something to do with the way the regulator works.

I think that you will find that as you approach full load on the generator the frequency will drop closer to or below 60Hz.
Possibly the reason that the makers bias it on the high side is that more equipment would be potentially harmed by too low an input frequency than too high an input frequency?
 
GoldDigger said:
The choppy waveform may relate mainly to the physical shape and orientation of the coils and the shape of the magnetic field. Or is may have something to do with the way the regulator works.

I think that you will find that as you approach full load on the generator the frequency will drop closer to or below 60Hz.
Possibly the reason that the makers bias it on the high side is that more equipment would be potentially harmed by too low an input frequency than too high an input frequency?
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I would have to agree with the first sentence which relates to the design and quality of the product. In the second sentence as for the voltage regulator, I cannot see how that has anything to do with the shape of the sine wave. As I see it a VR controls and stabilizes the gen RMS voltage, not the shape of the waveform.
The question I have is whether he measured the wave loaded or unloaded.
 
Is it in fact an alternator or does the generator generate DC an the use an invertor to convert to AC? With an alternater on would expect a sinusoidal wave form. With a SS invertor who know what the AC Weill end up being w/O appropriate filtering to smooth out the wave form to emulate an actual sinusoidal wave form as close as practical.
I worked on a heavier than heck old school generator (3-4kw?) with a mechanical centrifugal governor which I tached out to as close to 3600rpm and then checked the actual frequency. It blew me away as to how well it kept to maybe +1hz. Crazy!!! I never would have expected that. It amazed. That generator had to be from the 1960s. Yes, I do have small engine rerpair experience with B&S, techumseh, Kohler, kawazaki, Honda, etc. Anything from carbs to ignitions and getting gensets to run again after having left set with stale gas and not run for months/ years if often a challenge. Some carbs end up being trashed. When complete I always varify the voltage and fequency but quite often the gensets are used on construction job sites running power tools where finite power quality is not an issue anyway.
 
A centrifugal governor can hold much tighter regulation than the air vane used in inexpensive portable gensets. One percent does not surprise me at all.
In a car the electronic cruise control can often hold around 1 MPH out of 60.
It comes down to how much gain you can put into the control loop without risking oscillation.
 
GoldDigger said:
A centrifugal governor can hold much tighter regulation than the air vane used in inexpensive portable gensets. One percent does not surprise me at all.
In a car the electronic cruise control can often hold around 1 MPH out of 60.
It comes down to how much gain you can put into the control loop without risking oscillation.
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In the gensets thgast I worked on non had a B&S with the air vane governer! They must be reserved ft or the chepos.
With the older generators there is more play in the mech from the centrifugal mech at the engine where it goes thrtough the through the engine block to the linkages connecting to the throttle which often results in a bit of hunting.The throttle is very sensitive to the slightest movement of the linkage.
With the new engine designs the play in the various linkages is taken up with a small spring linkage which parallels the main linkage which takes any play out of the linkage which basically tighterns up the linkage resulting in better governing.
When adjusting the governed speed special attention must be paid to the lenkages from the centrifugal gov lever to the carb throttle. There have been occasions where we have added (modified) and older design by adding a spring.
Another pain in the butt is the lach of adjustments on the newer carbs. There have been times where a carb had to be replaced because it just would not function correctly.
 
GoldDigger said:
A centrifugal governor can hold much tighter regulation than the air vane used in inexpensive portable gensets.
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I have not seen an air vane governor on any modern small engine. They all see to have internal centrifugal governors. Likely for the very reason you point out, they where not very good.
 
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