PTO generator

[techman]

The motor is a 3/4 hp motor. 3/4 of 746 = 559 watts. It was drawing 362 watts running with just a grinding wheel. The hot steel was due to the fact that I was pressing on the grinding stone hard in an attempt to load it down (it did slow) to show the current under load. The 3/4 hp motor I tested came in at 362 watts running and under load it came in at 850.

You have completely missed the point of the test.

We don't care what the motor efficiency is, we are talking about generators starting motors and generators dip when motors start. What are we talking about here, an industrial application with high hp motors running at 440 volts? No people are using PTO gens to run their homes.

Sizing Gen-Sets For Large Motor Starting | Basics content from Electrical Construction and Maintenance (EC and M) Magazine

"Let's look more closely at a motor start. Induction motors have typical starting characteristics. The curve of motor current versus speed shows that during starting, the motor draws approximately six times its full load current; this current remains high until the motor reaches about 80% of speed. This high inrush current causes a dip in generator voltage. The electric power initially required by the motor (with the motor at standstill) is about 150% of rated power. The power required by the motor peaks at about 300% of rated power and 80% of speed with full voltage applied. But, the generator set supplies less than 300% power because starting voltage is lower than full voltage during acceleration, and because the generator set's rotating inertia transfers energy to the motor."

So you're wrong, 3x is all we need. It's an accepted standard. I employ it here and I'm off the grid running inverters and calculating using 3x for years. I haven't blown a fuse or stalled a motor. So if you think that you need 100x overhead than build it into your system, I don't give a fiddle. But tell me how long you've been running off the grid?

Geeze, how many links do I have to post showing this?

You want to be argumentative, find someone else, this is getting silly, the question is how much overhead do we need to start motors.

3 times! How many more links do you need to see?

By the quote referenced, 300% at 80% of speed does not support your argument. At the initial startup, from a dead stop, the current can indeed exceed 300% of FLA. Also one is not interested in total power, it is instantaneous current that can be the limiting factor. Above a certain current, the generator field will saturate, limiting available current. The worst case scenario is with split phase motors. The high starting current limits acceleration and at the same time lugs the generator voltage. The motor never accelerates enough to trip the start switch so the motor chuggs at low speed and high current, the gen set is pulled down and if an overload does not save the day, you could fry the generator or the motor or both.

Bottom line is that 3x FLA is a good RULE OF THUMB, but peal currents at initial startup can definitely exceed that value. Just look at the motor specs I posted earlier. Will the motor start if less than the typical peak is available, most likely it will, but a few may not.

paul

 

[Rob-D]

By the quote referenced, 300% at 80% of speed does not support your argument. At the initial startup, from a dead stop, the current can indeed exceed 300% of FLA. Also one is not interested in total power, it is instantaneous current that can be the limiting factor. Above a certain current, the generator field will saturate, limiting available current. The worst case scenario is with split phase motors. The high starting current limits acceleration and at the same time lugs the generator voltage. The motor never accelerates enough to trip the start switch so the motor chuggs at low speed and high current, the gen set is pulled down and if an overload does not save the day, you could fry the generator or the motor or both.

Bottom line is that 3x FLA is a good RULE OF THUMB, but peal currents at initial startup can definitely exceed that value. Just look at the motor specs I posted earlier. Will the motor start if less than the typical peak is available, most likely it will, but a few may not.

paul

I looked Paul, but empirically I have never had a motor or generator problem in several years using the 3x ratio, nor have I heard of anyone else having a problem. As the gen set drops the motor rises enough to start. I've never seen it come even close, I've seen lights dim but the motor always starts. You could use a gen set with 6x overheard but now you have a system that uses more fuel. I just heard that there are people stil without power from Sandy, every ounce of fuel saved means longer run times. I say get the smallest gen set you can to do the job.

OK, how much overhead do you and Larry think is needed?

 

[Rob-D]

Well put and I agree fully.

Really?

Than how much generator overhead do you think the average homeowner needs to run the motors, appliances, etc. in his or her house?

Next question, how long have you actually been doing it on a continuous basis?

 

[Shimon]

A PTO generator was one of the first implements I purchased as we lose power often. I mounted it in a corner of my shop and put in a removable hatch so I can back up the tractor to the shop and put the PTO shaft through the hatch. I also put in a multimeter on the wall so I can adjust the throttle and read the frequency (and amps/watts/volts) while standing near the tractor. The generator has served us well and will run the whole house (hot tub included) at 13kW. Plus we have a 500 gallon tank of diesel since we have a diesel furnace so fuel is never really an issue.

 

[sdkubota]

Sweet set up.

 

[DarkBlack]

A PTO generator was one of the first implements I purchased as we lose power often. I mounted it in a corner of my shop and put in a removable hatch so I can back up the tractor to the shop and put the PTO shaft through the hatch. I also put in a multimeter on the wall so I can adjust the throttle and read the frequency (and amps/watts/volts) while standing near the tractor. The generator has served us well and will run the whole house (hot tub included) at 13kW. Plus we have a 500 gallon tank of diesel since we have a diesel furnace so fuel is never really an issue.

QUOTE]

A tractor "glory hole"!:laughing:

 

[DarkBlack]

Well, Im less confused about where youre wrong than you are. You seem to lack appropriate attention span on pertinent parameters. This is going nowhere.
larry

Early in this thread I quized him on some of his posted 'expert' material to feel out, if he really understood the very text he was posting. Questions anyone, who has been in the businees, would know.
Let's just say... that he didn't even know that was, what I was doing...

 

[SPYDERLK]

Great, denigrating the conversation to insults. Why don't people realize that ad hominem attacks just reflect on their own character?

As for my attention span, I'm bored, to busy to look back and the issue is a moot subject to me after link after link showing that 3 times overhead is the accepted standard.

I try not to recriminate.
...larry

 

[GPintheMitten]

My 50kw Winpower is no typo. It could punch out 50kw continuosly with the JD 4020. My F-935 is/was 22 hp when new. But, my demand is not 50kw, its probably less that 6kw. No matter, the F-935's motor can deliver enough kinetic energy for the Winpower to convert it to electricity for my use. If my demand was for a higher electric power than is equivalent to the 22 hp on the mower, then it would brown down. Or I could throw my JD 1070 back on (35 hp) and see if that's enough motor (18kw load). But the alternator is wired to handle the current equivalent of 50kw service in case I need to run a small town. Then I would need the 4020 (100 hp?) to deliver the equivalent engine hp.

When I bought the Winpower at a farm auction, all the buyers were told it would take 100+ hp to run it. But I was not going to dry corn, I wanted a furnace, well, lights, fridge, TV/radio and a battery charger. So I was the only one who bid after a lot of discussion and opinions by the know-it-alls : $600. I can still hear the auctioneer yelling: "SOLD. The auction is today folks!"

I stand corrected. I didn't know you could run such a large generator on a lower HP pto.

 

[RoyJackson]

A PTO generator was one of the first implements I purchased as we lose power often. I mounted it in a corner of my shop and put in a removable hatch so I can back up the tractor to the shop and put the PTO shaft through the hatch. I also put in a multimeter on the wall so I can adjust the throttle and read the frequency (and amps/watts/volts) while standing near the tractor. The generator has served us well and will run the whole house (hot tub included) at 13kW. Plus we have a 500 gallon tank of diesel since we have a diesel furnace so fuel is never really an issue.

Nicely done!! And has given me some ideas!

 

[Gator6x4]

Roy a neighbor did something similar. He used a "Pet Door" he found somewhere at a reduced price. Looks good, works well.

 

[dex3361]

Really?

Than how much generator overhead do you think the average homeowner needs to run the motors, appliances, etc. in his or her house?

Next question, how long have you actually been doing it on a continuous basis?

Rob

1) Depends on the house and what he is going to run.

2) For only about +-30 years. I hook up my house generator every time I lose power. I also hook up emergency generators industrially ranging in size from a 30KW that I hooked up today (very nice Cat unit) to a 1.2 Megawatt generators that is powered by a V16 Cummins diesel engine(my biggest so far and I hated the cables they were heavy).

 

[aczlan]

I now know what to do if we end up with a PTO generator, Thanks for the pictures.

Aaron Z

 

[RoyJackson]

Roy a neighbor did something similar. He used a "Pet Door" he found somewhere at a reduced price. Looks good, works well.

No doubt!
I haven't got a PTO genny yet (it's in the near future though) and I'm reading these types of threads eagerly. Loads of great info here! And not just this thread.
One thing does concern me is theft which that's taken care off. The other is the exposed outlets in inclement weather. Shimon's and your posts takes care of the exposed outlets aspect.

 

[joshuabardwell]

I know what you mean, but I'm lucky and have a 5500k from around 2000. That said we have been looking at a whole house backup NG unit from Generac natural gas 14kw. Anyone else using the PTO units... wonder how they work for powering computers? Prayer for you over their... wer're going to hit over here in W PA too.

IMO (and I'm not an electrical engineer, but I am a geek), the main problem with computers and generators is when the generator is under-specced for the load, causing voltage drops. People say that conventional (non-inverter) generators produce "dirty" power, and if you look at the waveforms on an oscilloscope, you'll see the difference, it's true. The conventional generator doesn't produce a pure sine wave. But what I am skeptical about is whether that "dirty" power can actually damage electronic equipment. If you think about it, a computer operates internally purely on DC. And the computer's PSU specifically has the job of converting incoming AC to clean, pure, reliable DC. So if the incoming AC is not a perfect sine wave, it seems like the worst that will happen is you will burn out your computer's PSU. But realistically, I think that most PSU's these days are robust enough to handle a little bit of not-quite-pure sine wave without breaking a sweat.

IMO (and, remember, not an EE--just a geek) if you don't overload your generator and if you make sure it's putting out pretty close to 60 Hz, you should be good to go.

 

[Gator6x4]

The neighbor I referenced used what he refered to as "Trailer or Mobile Home" service wire. Supposed to carry 100 AMPS. He direct buried from garage/workhop to house. Used conduit to peneterate the wall of the garage and hooked to the generator. He has a lean too, equipment shed on the rear of the garage/workshop. He parks the tractor under the shed, runs the PTO shaft thru the pet door, connects everything and starts the tractor. Tractors in the dry and generator and all connections are inside the garage/workshop in the dry. As I said previously, looks good works exceptionally well. He never has to "Rough It". Always has well water, hot water for showers, hot meals, tv, computer access, etc.

 

[DarkBlack]

Josh,
You are better off with a lightly loaded genny than no load. I would always connect some light resistive loads like incendescent light before powering a critical electronic load like a computer.

 

[SPYDERLK]

A PTO generator was one of the first implements I purchased as we lose power often. I mounted it in a corner of my shop and put in a removable hatch so I can back up the tractor to the shop and put the PTO shaft through the hatch. I also put in a multimeter on the wall so I can adjust the throttle and read the frequency (and amps/watts/volts) while standing near the tractor. The generator has served us well and will run the whole house (hot tub included) at 13kW. Plus we have a 500 gallon tank of diesel since we have a diesel furnace so fuel is never really an issue.

QUOTE]

A tractor "glory hole"!:laughing:

I have that same genset mounted on a pressure washer platform/cart I bought from NorthernHyd. I set up the frame with a 3pt drawbar and cobbed in a toplink fastening point on the handle. So ... the wheeled cart can attach to the 3ph and go anywhere the tractor can. When thru using just disconnect and wheel into the basement.
larry

 

[daybreak1998]

they are getting out of the PTO generator business. I bought out about the last 40-50 PTO generators they built, but they are done manufacturing. The company (Dynatech) is still in business and doing fine, they will continue to stand behind any warranty claims. They just where not finding the business profitable any longer.

Howdy Neil,
I am the proud owner of a Tiger Power 30KW PTO generator from Messick's (back in Oct 2010). I am very happy with my purchase, and like the build quality of the generator.:thumbsup:

 

[BrianW]

Yeah, but what's your favorite color?

If anyone wants to discuss the airspeed velocity of a fully laden European shallow I'm here...:drool:

Don't be bringing African swallows into the discussion.