PTO generator/volts vs hertz

[Hughman]

PG&E provided me with an opportunity to exercise my generator and transfer switch a couple of weeks ago courtesy of a 6 hour outage. The transfer switch and generator operated flawlessly. The only blip I heard from the tractor was when I kicked on the well pump (800' deep).

Question I have is which is more important, volts or hertz? When I hook up a meter to one leg I read 115v @ 60hz.

 

[Hughman]

If I bump the tractor rpm up a bit I get 120v @ 61.5hz.

My primary concern is the well pump.

 

[techman]

Not easy to say which is more important. Many devices can tolerate deviations in Hz, including motors, lights, heating devices and most electronics. Voltage can cause some issues. Too high can potentially damage some devices and very low can result in motor issues. If you keep the voltage around 120 and Hz are off a few you should have no problems.

 

[workinonit]

One is no more or less important than the other. Voltage can deviate based on the amount and types of VAR loads you are running. Frequency deviates based on how good your tractor governor is when kW load is added and removed. In larger generators voltage and frequency can be controlled separately. Our smaller gensets don't have that capability so we have to find a happy medium. Generally speaking if you control frequency to 60 Hz voltage will be in a safe band.

 

[steve tym]

As Hz go up, the speed of the motor will go up and the amps will go up. At some point over heating the motor. Both are important.

 

[DarkBlack]

As Hz go up, the speed of the motor will go up and the amps will go up. At some point over heating the motor. Both are important.

That’s incorrect. At a given voltage, AC motors draw more current (amps) and can potentially overheat when the power frequency is below specified. You have it backwards

 

[ponytug]

PG&E provided me with an opportunity to exercise my generator and transfer switch a couple of weeks ago courtesy of a 6 hour outage. The transfer switch and generator operated flawlessly. The only blip I heard from the tractor was when I kicked on the well pump (800' deep).

Question I have is which is more important, volts or hertz? When I hook up a meter to one leg I read 115v @ 60hz.

One point about the legs. US split phase has two hots and a neutral. Hot to hot should be close to 240VAC, perhaps a bit above if you have a long cord to the house to get 240 in the house. Depending on the generator, it may or may not have a great ability to keep the hot to hot at 240 and simultaneously keep each of the two hot to neutral voltages at 120VAC. So, next time, I would make start by making six voltage measurements with no load, and then again with loads on both hots;

• Hot to hot
• Hot #1 to neutral
• Hot #2 to neutral
• Neutral to ground voltage
• Hot #1 to ground
• Hot #2 to ground

Ideally, use multiple meters to measure both hot legs at the same time. You may have measured the voltage on a heavily loaded leg, while the other leg was lightly loaded.

Frequency (Hz) is straight up what the tractor spins the PTO and generator at.

You might look into your PTO generator voltage regulation a bit, if you are up to it. Many generators have ways to adjust the voltage, some of them very readily from the control panel, some not so readily.

All the best,

Peter

 

[RjCorazza]

I'm not as electrically savvy as most of you, but my old Onan 1800 rpm RV generator was adjusted soley to the hertz (60hz here in the States), and there was an acceptable voltage range listed. It's been a long time ago, but I recall 110v being the lower acceptable voltage. Certainly not gospel, but that's what the OEM recommended.
Anyway, I adjust my PTO generator to 60hz while under load and the voltage is always in a reasonable range. The tractor grunts a little when the big loads turn on, but the voltage and hertz remain relatively stable.

 

[etpm]

Here's the way induction motors work: when the voltage drops the motor slows so then the motor will draw more current, amps, in an effort to speed up. This extra current causes heating in the motor windings. If the voltage stays low for a long time, and if the power supply can supply enough current, the motor will overheat. This is why refrigerators will burn out compressors during a brownout, when the voltage drops too much. Frequency variations of 5 Hz up or down will not hurt an induction motor. But low voltage can. That said, 115 volts is OK. Modern motors, motors made in the last 60 years or so, maybe even longer, are made to operate properly anywhere from 110 volts to 125 volts. This is because of the variation in the supplied voltage from the power producers.
Eric

 

[garry1p]

Both HZ and voltage are important.
The power company holds HZ to +/- 1% for a reason and voltage +/- 5%.

Rule of thumb for a generator acceptable voltage fluctuation low 114VAC maximum 126VAC frequency 59.5/60.5
An air conditioner will burn itself up at voltage below 108V very quickly due to over heating when AC is over 136VAC motor and compressor will be toast in very short order.
Same with frequency to high and electric motors run to fast, to low motor runs to slow both cause overheating.

 

[5030]

All too complex for me. I just let both my Generac's adjust themselves internally. The both have electronic voltage and hertz controls.

One thing I never do is load them to the maximum output and after 15 years all has been good.

One thing I just did was I took the 20KW unit that runs the house and removed all the internals from the original steel cabinet and installed all the internals in a Generac supplied aluminum cabinet as the OEM steel cabinet was suffering from terminal corrosion. The new powder coated aluminum cabinet set me back 5 grand (special order from Generac) but 5 grand was cheap compared to a new 20KW unit. Retail on a new 20KW Generac is pushing 15 grand today. 5 versus 15 in my view was a no brainer.

I was pleasantly surprised that Generac made an aluminum refit cabinet but then a lot of them were sold with steel cabinets and I bet a ton of them are suffering from terminal corrosion. They should have never sold them with steel cabinets in the first place.

The instructions were a bit cryptic but I figured it out no issue. Generac supplied all the necessary hardware as well and even a cute 'Generac' decal I threw away.

First time I installed the unit on a pad filled with per gravel bordered with .40 retention 4x6 boards. This time I poured a 6" thick concrete pad with rebar in it and sat the new unit on top of the concrete. I set it so I didn't have to remove the grounding rod as Generac units are all floating ground and must have the chassis earthed. Hopefully I won't be around long enough to worry about it again.

The 35KW unit I have next to the shop that runs the shop and the outbuildings came with an aluminum enclosure sitting on top of a 150 gallon diesel tank I never use. I plumbed the diesel feed into my 500 gallon bulk tank and left the integral tank dry. After 15+ years of service, the JD Turbo diesel runs like a top with regular maintenance and never fails to pick up the load when the utility fails which is often out here. Same with the 20KW unit that feeds the house but that one is on propane. I have 3 500 gallon owned bottles in the side yard and we heat the house with it as well.

 

[DarkBlack]

Rule of thumb for a generator acceptable voltage fluctuation low 114VAC maximum 126VAC frequency 59.5/60.5

Your 60 +/- 0.5 hz spec, is reasonably expected for inverter, and large electronically governed generators, but for common mechanically governed generators, the frequency is definitely going to vary more, and drop more like 1-1/2 hz, from no load to full load. You’ll find most PTO generators that are sized up close to capacity of the mechanical governed tractor would also drop as much, or more. My tractor has a lot of governor speed sag. Mechanical governors require speed sag to operate.

 

[LouNY]

It wasn't very long ago when our power was considered 110/220 volt, now it seems people think it should be 120/240 volt.

"
Many people refer to the voltage at the electrical outlets as 110 volts. Others routinely call these 120-volt outlets. If you plug almost any appliance into these plugs, the appliance works fine in either instance. Do some power companies deliver 110 volts and others 120 volts? What is the real story about 110V vs. 120V?

In the United States, there is no difference between a 110-volt outlet and a 120-volt outlet. The standard followed by power companies is to deliver electrical service to homes at 120 volts plus or minus a ten percent variance. Appliances in the US market are designed to operate within these variances. "

Your generator should have an adjustment for the voltage if you are worried about it. If it has automatic voltage regulation it will be adjustable, you may have to remove some tin work to find the regulator.

 

[Hughman]

The generator in question is a WinCo 15kw. The only adjustment without opening it up is the tractor throttle. Sounds like I'm pretty close either way. I'm not worried as much about the 110 appliances inside the house as I am about the 220 pump motors. The whole point of this gene over my portable is that I can run the well to get water during extended outages.

 

[ponytug]

The generator in question is a WinCo 15kw. The only adjustment without opening it up is the tractor throttle. Sounds like I'm pretty close either way. I'm not worried as much about the 110 appliances inside the house as I am about the 220 pump motors. The whole point of this gene over my portable is that I can run the well to get water during extended outages.

I am glad that it works for you now. I would check with Winco if you want more volts; their manuals don't include voltage adjustments as far as I know. Their generator voltage regulation seems to be a fixed voltage/Hz system.

All the best,

Peter

 

[DarkBlack]

Their generator voltage regulation seems to be a fixed voltage/Hz system.

If the output voltage is fixed to rpm’s, then that’s pretty much no real voltage regulation
Imagine if vehicle alternators were like that… discharging your battery at Idle, fry everything electrical when you rev it up

 

[LouNY]

The generator in question is a WinCo 15kw. The only adjustment without opening it up is the tractor throttle. Sounds like I'm pretty close either way. I'm not worried as much about the 110 appliances inside the house as I am about the 220 pump motors. The whole point of this gene over my portable is that I can run the well to get water during extended outages.

It looks like your generator is a capacitor controlled voltage regulation of +- 5%,

ADDITIONAL INFORMATION​

Standby Watts - 15,000
Running Amps - 62.5
Voltage Output - 120/240 Volt Single Phase
Voltage Regulation - Capacitor
120V Receptacles - (1) NEMA 5-20 20A Duplex
120/240V Receptacles - (1) NEMA 14-60 60A
PTO Input Speed - 515 RPM
Dimensions - 25.1" x 14.5" x 20.6.3"
Shipping Weight - 232 lbs.

The only way to adjust the voltage up is to over speed your hz by a touch.
Some people have changed the capacitors to adjust the voltage, that would be a hit or miss adjustment.

 

[etpm]

The generator in question is a WinCo 15kw. The only adjustment without opening it up is the tractor throttle. Sounds like I'm pretty close either way. I'm not worried as much about the 110 appliances inside the house as I am about the 220 pump motors. The whole point of this gene over my portable is that I can run the well to get water during extended outages.

A 15 kw generator should be plenty to run your deep well pump. I dunno what the HP of your well pump is but a residential pump shouldn't be that high. One HP is .75 kw so your pump would need to be plenty big to stress a 15kw generator. Truly the biggest problem for the well pump is low voltage, not frequency. As long as the voltage stays above 220 volts you don't need to worry about a drop in frequency to even 58 Hz. The pump motor won't care about a slightly lower frequency. The real killer for induction motors is low voltage because as the motor slows due to low voltage it will draw more current in an effort to speed up, which causes extra heat. Fortunately your well pump, if submerged, will have all that water surrounding the motor to cool it. On the other hand, if you have a surface mount motor spinning a shaft that goes down the hole, you can go to the pump motor physically and feel how hot the motor is. If you can't hold your hand against the motor for a minute or so it is probably running too hot. Still, your well pump probably runs intermittently so overheating is most likely not a problem. I don't think you need to worry. I run my 1/2 Hp well pump from a generator that is just OK as far as frequency and voltage. I just make sure the voltage stays above 220 volts and don't worry at all about my well, freezers, or refrigerator. The well wants 220 volts and the appliances 110 volts minimum. My generator puts out about 225 volts. The frequency varies about 3 percent up and down but mostly stays at pretty close to 60 Hz. But the power is full of harmonics. The motors just don't care.
Eric

 

[ponytug]

A neighbor down the road has a well with the water table over 700' deep, that's 300+psi at the pump, and starting that is not a small amount of power. Voltage matters, but so does how long the voltage is out of specification. One cycle, not usually an issue, and 30 seconds is a very different story. I would be careful about generalizing about "deep" wells, as the definition of "deep" varies around the country.

I would point out that a generator's power rating may be true in real world conditions, or may not be, and the tolerance for starting large motors varies considerably amongst generators of similar nameplate ratings, just like the big variation in actual engine HP ratings when a 3rd party puts the vehicle with water pumps, alternators, power steering and all, those items, on a dynamometer... I have a generator (older) that doesn't do much beyond its nameplate, one that happily does 15% more (also not young), and one from the nineties that leans into 50% over nameplate with no issues. YMMV.

All the best,

Peter