64 hertz and a Kill-a-Watt

[Rod in Forfar]

Portable generators, not connected to a utility system, need not tightly regulate their frequency, because typical loads are insensitive to small frequency deviations. Wikipedia

Yesterday I tried connecting my Bolens G174 (15 hp PTO at 740 rpm) to my newly-acquired BAUMALight 7.2 KW PTO generator. It ran the generator up to 120 watts on the gauge with no difficulty at about 2/3 engine revolutions, even when I plugged in my band saw with its 1.5 hp 120 volt motor.

But when I plugged in my new Kill-a-Watt meter as well, I found that the heavy motor had dragged the voltage down to 108, so I increased throttle to peg the voltage at a comfortable 128 volts. But then the frequency went to 64 hertz.

So my question is: which is more critical in generator output, voltage or frequency?

Statistics confuse; stories make me understand. Does anyone have any useful Kill-a-Watt anecdotes to illuminate things?

 

[tessiers]

Since the voltage is supposed to be 120 volts and the frequency 60 hz, you have them both over by 6.666%. I think if you back it down so your voltage is a comfortable 120 volts your frequency will be right as well. You are right at the limit of the engine HP, but a simple band saw should not draw enough to effect the generator much. Your governor should be adjusting the throttle to compensate for load, if you have to adjust the throttle manually something is wrong. I am used to farm tractors with governors, so maybe the bolens doesn't have a governor, if so I would be careful about running a generator with it. If you have a heavy electrical load and shut it down anything else in the system would get an immediate voltage spike, until you could adjust the throttle again. I think the voltage is more critical then the frequency but I also think high voltage is just as bad as low voltage, I would be cautious of both. Going by memory here but I think the NEC recommends staying within 5% on voltage. Both 108 v and 128 v are out of the 5% range.

 

[Soundguy]

within the wattage limits of the gen.. it should make 120v ideally at 60cps.. unless you have more than a 7200w laod.. and also assuming you have enough pto hp to maintain it.. and maintain it steady. I would back the cps down to 60 and observet he line voltage. if the reg is anywhere near 'good' you should be right in line with utility....

 

[buickanddeere]

Had 120Volts not 120 watts. Frequency is vital and must be maintained at 60+- 2Hz.
The voltage regulator is either non existent and a simple cheap rectumfire is used to power the generator's excitation windings. Or if equipped with a voltage regulator it's failing to increase excitation voltage and current to maintain stator voltage.
108V is getting into brownout voltages and equipment should not be operated that low.

 

[Soundguy]

at 60hz it sure should not be putting out 108v with a load under rated spec.. and with enough hp to carry said laod.

even passive capacitance based vreg.. if so..it's defective..

 

[Rod in Forfar]

at 60hz it sure should not be putting out 108v with a load under rated spec.. and with enough hp to carry said laod.

even passive capacitance based vreg.. if so..it's defective..

Under heavier loads on 220v the 17 PTO hp Kubota actually increased voltage. The governor's more alert, I guess. As well, it was running at 2500 rpm to get 540 on the PTO vs the casual lope of the Bolens, throttled down from 740 in the second pto gear.

So to answer the question: "Can a Bolens G174 run a pto generator?" I'd answer: "Only for light loads, or in an emergency. It lacks the reserve of torque with its hinky pto gear ratios to match its power to the needs of the generator." It might provide useful lighting or run the odd power tool, but not both.

BTW: That band saw draws 12 amps on 120v.

 

[Rod in Forfar]

Both 108 v and 128 v are out of the 5% range.

On Sunday afternoons in rural Eastern Ontario I have often seen the voltage creep up as high as 260v on 220. My planer can handle heavier loads then than at other times in the week.

When we set up the generator panel for the new equipment (one circuit deleted, two added) my electrician friend observed the voltage climbing to 128v due to the action of the Kubota's governor when we applied loads. He thought this was o.k. because the motors were running well and the florescent lights in the basement no longer flickered.

Years ago he served his apprenticeship in hydro stations in Newfoundland. He did not have a frequency meter among his tools, though.

 

[Ken45101]

A few Hertz different in frequency will not hurt anything. Most consumer electronics will run on 50 or 60 Hertz.

Nominal line voltage is 120V +/- 10% (108-132) although residential service should be +/- 5% (114-126). We often ran 128v here before they put in the new lines.

Motors under load run better with slightly higher voltage than with slightly lower voltage.

 

[Midniteoyl]

A few Hertz different in frequency will not hurt anything. Most consumer electronics will run on 50 or 60 Hertz.

Nominal line voltage is 120V +/- 10% (108-132) although residential service should be +/- 5% (114-126). We often ran 128v here before they put in the new lines.

Motors under load run better with slightly higher voltage than with slightly lower voltage.

Agreed...

And at the slightly higher voltage, you are using slightly less amps which means less heat in a motor.

 

[Soundguy]

Agreed...

And at the slightly higher voltage, you are using slightly less amps which means less heat in a motor.

i see low voltage kill many motors. too much amps to get the correct power. burns small wires.. etc...

can weld contacts too.

 

[Ken45101]

Yes, low voltage will overheat motors more than high voltage.

 

[CobyRupert]

[But when I plugged in my new Kill-a-Watt meter as well, I found that the heavy motor had dragged the voltage down to 108, so I increased throttle to peg the voltage at a comfortable 128 volts. But then the frequency went to 64 hertz.

1st: To make sure we're not talking about voltage drop in cables due to current, (versus a voltage drop due to tractor rpms dipping because of load): where in the system did you plug the kWatt meter in?

You say the motor dragged the voltage down to 108V, but I suspect the hertz also got dragged down to ~54 Hz at the same time, because the Bowens rpms got dragged down by the load? If so, then with the motor running, couldn't you then bump the throttle so meter reads 120V/60Hz with the motor running? (Or did you say that? That is, can we assume the throttle setting for 120V/60Hz with the motor running is 128V/64Hz measured with the motor off? )
No system is static when load are switching on and off. It's better to be on the +10% side than the -10%.
Higher voltage usually equals less current which equals less killer heat in the system.
Without a governor, aiming to hit the middle with expected loads running, and being a little high when there not, might be the best you can do.

 

[DarkBlack]

Some questionable advice on this subject, thar be here.

 

[buickanddeere]

What is the voltage with the frequency at 60Hz and the motor operating ?

 

[Rod in Forfar]

What is the voltage with the frequency at 60Hz and the motor operating ?

I'll have to hook the Bolens up and play with it again. I think it was 108v, though.

What I have figured out from personal messages and posts here is that the Kubota's a better choice for serious generator operation largely because it produces 540 rpm pto. The Bolens should work for projects away from the shop, but I would only run the house on it in an emergency. Next up for generator duty is the 1947 Massey Harris 30. A fresh engine, large gas tank and easy winter starting sound tempting.

 

[Midniteoyl]

Some questionable advice on this subject, thar be here.

Such as?

 

[buickanddeere]

Standby power is a topic near and dear to myself. I would like to see my neighbour who is 325 miles away keep the pipes from freezing and the icecream from melting.
I should ask, what kind of transfer switch is being used?

 

[jenkinsph]

When all is said and done I think the Kubota is going to be the best fit for your use. Might wan't to consider the additional tank for extended run I suggested in your first thread. I agree that it is good to know what the other tractors can do in a pinch as their backup can provide peace of mind.

 

[Rod in Forfar]

Standby power is a topic near and dear to myself. I would like to see my neighbour who is 325 miles away keep the pipes from freezing and the icecream from melting.
I should ask, what kind of transfer switch is being used?

The transfer switch is a 30 amp panel wired into the other two 200 amp panels in the house, with key circuits redirected to it. The extra panel was needed to tidy up the wiring when I renovated half of the large house.

The generator panel has a master switch, moving from "line" to "off" at centre, to "generator" when the lever is fully thrown. When the grid comes back up after an outage the non-essential items light up again, so we know it's time to switch back from the generator.

 

[buickanddeere]

Good to know. We have so many d*m fools here that won't believe back feeding a welder receptacle is looking for trouble.