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.