PTO generator

[brin]

One option is when you get a well pump pick one with little or no inrush.

Most well drillers don't have any idea of this or care about the inrush they want to sell you well with a pump in it more money in their pocket.

The grundfos pump I have at 450 ft starts and runs on a 3000 watt invertor with out batting a eye.
the quick rule of thumb if you got a cheap pump you will have a high inrush.


SQ | Grundfos

I have a drilled well 175 ft. deep...25 GPM....and I also have a 20KW PTO generator but I like what you have posted about this pump...What is the cost and would it work with my drilled well...? I went to the co. website but it is above my pay grade....thanks...

 

[Charlesaf3]

I obviously agree with spiderlk. That said, I also do agree that 3x load, especially if there is any sort of inertial/flywheel effect, should do. But I have been unable to run a big fridge or pump off a cheap 5k genny before, much to my annoyance.

I have 250gallons of diesel in a tank in one situation. It takes me 10gallons a day to run a b3030 full out. 25 days. I put power service in and have never had problems in mass winters. If I don't run full out, I see no issue with a month. And diesel is less sought after during outages, generally, and you can drive to get it.

Other situation is hard piped natural gas. Frankly I think this is the ideal.

If a month worth of diesel or hard piped natural gas isn't enough, my family will be getting out of dodge

I like pv, but without subsidies, or off grid issues, it just makes no economic sense currently.

 

[Rob-D]

I obviously agree with spiderlk. That said, I also do agree that 3x load, especially if there is any sort of inertial/flywheel effect, should do. But I have been unable to run a big fridge or pump off a cheap 5k genny before, much to my annoyance.

I have 250gallons of diesel in a tank in one situation. It takes me 10gallons a day to run a b3030 full out. 25 days. I put power service in and have never had problems in mass winters. If I don't run full out, I see no issue with a month. And diesel is less sought after during outages, generally, and you can drive to get it.

Other situation is hard piped natural gas. Frankly I think this is the ideal.

If a month worth of diesel or hard piped natural gas isn't enough, my family will be getting out of dodge

I like pv, but without subsidies, or off grid issues, it just makes no economic sense currently.

Tell me how much you like "hard pumped natural gas" when a quake hits and manhole covers are going 20 feet in the air.

PV is feasible, you have to install it yourself but right now I'm getting promos from dealers for interties with Enphase micro MPPTs for $1.25 a watt, all you need are the mounts. Even without the 30% payback that's pretty darn cheap. Would I give up my PV for diesel or gas? Never!
25 days is a very short time when there's a major catastrophe. One relay in Canada took out half the East coast, that's how fragile the grid is.

 

[sdkubota]

You will have trouble finding a genset that big that runs on NG. There are a few that use car engines, but you are mostly into diesel at that power. Unlikely that you will ever match the utility prices since they too are switching to NG at much higher efficiencies in generation.

paul

I believe many areas in the Hurricane Sandy wrecking zone had their natural gas shut off to prevent fires and most of those areas still do not have that utility restored.

 

[Rob-D]

Im glad this is finally being straightened out. All motors draw locked rotor current at startup because the rotor is stationary at that time. This is a very short term event that you will need a peak holding meter or an oscilloscope setup to capture because the current drops quickly as the motor starts to turn and continues to drop until it reaches speed. It is on the order of 4x or more of full load current. If this current times the Voltage exceeds the gen rating the gen voltage will buckle immediately. If it drops too much a motor with load wont start. A well motor starts without load , but immediately begins to develop an increasing load as it speeds up. This situation allows reliable starts at only 3x and lets you get by on a smaller gen.

Also, but not in your post, any suggestion to use 746 input Watts as equivalent to a 1HP motor will mislead the unwary. Virtually all motors use more than 1KW per HP. Actually it is a very good motor that can achieve that efficiency. And, as above, even a lightly loaded 1HP will still exhibit the high locked rotor initial current 4x above nameplate. Should this cause gen V to buckle it will cause big problems with other motors that may be running. Refrig or AC compressors may stop and take down the system. Multiple motors running simultaneously and cycling on gen power are going to cause an issue with systems not having ample surge capacity. Thats why its so good to oversize the gen while sizing the engine to supply the running load. The gen doesnt buckle and inertia controls V drop thru the surges of startup loads.
larry

Good, now tell me how much starting motor reserve generator manufacturers recommend? How about 3 times. Now let's take a motor with 90% efficiency, 746/.9=828.9 watts. OK, now let's take some empirical measurements:

3/4 HP motor FLA 11.4 amps. Running a grinder: actual watts used 362! (only load is the grinding wheel) Now let's put a heavy load on that grinder with a chunk of steel: 850 watts and that's with the steel getting to hot to hold.
So what exactly are we talking about here?
You want to put a scope on it to see the instantaneous power? Are you kidding? I'll tell you what, I have instruments here that can measure down to nanoamps, don't let me embarrass anyone with more real life tests.
And a locked rotor is not starting inertia from zero rpms, go back and read my post on how locked rotors blow fuses.

How about 3 times is all anyone needs to know.

 

[Rob-D]

I believe many areas in the Hurricane Sandy wrecking zone had their natural gas shut off to prevent fires and most of those areas still do not have that utility restored.

Of course, you can't have hard lined gas on when you have major events. It's just common sense.

 

[techman]

Rob-D

The starting current is generally 6 times higher for many motors. I have attached a data sheet for a Taco-Westinghouse 3/4 HP we used on a recent project. This initial current is short lived, 10-20 mS. You don't blow fuses or breakers because they are time-current devices, and will hold high currents for short duration. Look up an I-T chart for a typical device. The current you can see with a clamp on will typically show about 3 times on a peak hold reading. As long as you can get the motor moving on the initial start, the current will drop quickly. The biggest problem today is that generators are made as cheap as possible, and have limited surge capacity. The inertia of most engines will get you through much of the inrush, but if the gen does not have enough iron and copper, you can get into saturation on the core of the stator, and the max current is capped at a value that may not be high enough to get a motor started. High surge rating on a genset is worth the extra money, if you can find it.

Your suggestion that solar is the best solution also may not always work. I have 9.2 KW of grid tie solar. No battery, but if I did I would note that the day before and for several days after the storm, the low clouds limited my PV output to well below what would be needed to maintain the house in any comfort, and keep the food frozen. So even with batteries, unless you have a lot of batteries, you would only last a day or two without full sun.

paul

 

[PineRidge]

I just purchased a 15kw Rural King pto generator for my 35 hp, L3400. I ran it the other day and couldn't believe howeasily the tractor handled it at the 540 rpm level. I wasn't at full output by any means on the generator but the tractor wasn't working hard at all.

They say you should be able to run that gen set on a 25 HP tractor so you have a good reserve.

 

[Rob-D]

Rob-D

The starting current is generally 6 times higher for many motors. I have attached a data sheet for a Taco-Westinghouse 3/4 HP we used on a recent project. This initial current is short lived, 10-20 mS. You don't blow fuses or breakers because they are time-current devices, and will hold high currents for short duration. Look up an I-T chart for a typical device. The current you can see with a clamp on will typically show about 3 times on a peak hold reading. As long as you can get the motor moving on the initial start, the current will drop quickly. The biggest problem today is that generators are made as cheap as possible, and have limited surge capacity. The inertia of most engines will get you through much of the inrush, but if the gen does not have enough iron and copper, you can get into saturation on the core of the stator, and the max current is capped at a value that may not be high enough to get a motor started. High surge rating on a genset is worth the extra money, if you can find it.

Your suggestion that solar is the best solution also may not always work. I have 9.2 KW of grid tie solar. No battery, but if I did I would note that the day before and for several days after the storm, the low clouds limited my PV output to well below what would be needed to maintain the house in any comfort, and keep the food frozen. So even with batteries, unless you have a lot of batteries, you would only last a day or two without full sun.

paul

Yes, and if you look back I said inrush current is a non sequitur. For those of you here who don't understand what a 20 ms period of time is let me enlighten you:

Let's say a car is moving down the road at 60 mph, how many feet does it move in 20ms?

60*5280 = 316,800 feet in one hour at 60 mph; in one minute it moves 316,800/60 or (you guessed it) 5280 feet; in one second it moves 5280/60 or 88 feet:20 ms = 20/1000 or .020 seconds; 88 feet times .020 =.... drum roll ... 1.76 feet, in 10 ms it moves 10.5 inches!. 20 ms? You can't even blink that fast. I've designed circuits where LEDs change state faster than that and you can't see the change. If your lights blinked that fast you couldn't see the change. Now how many people think that their generator sees that? Put me on the none list.

As far a alternate energy goes, it is the future and while your intertie might not save you if all you have are solar panels it will save you if you have, PV, wind and hydro. Just PV and wind compliment each other very well and what do we get in storms? Wind and lots of it! So will my system keeps going regardless what happens to fuel and what happens to the grid?
Yes.
The point I'm making is that it's important to understand that only a renewable environment can sustain you indefinitely. Anytime you rely on fuel you become victim to shortages and price hikes. Land is power, unfortunately the forces that be would rather you didn't think in that light. What just happened? We had a storm and people ran to the food stores. Why? Because they rely on outside sources to survive, they've been very educated by corporate America to do that. Go read about a guy named Edward Bernays and how he helped sculpt the American mind.

 

[SPYDERLK]

Good, now tell me how much starting motor reserve generator manufacturers recommend? How about 3 times. Now let's take a motor with 90% efficiency, 746/.9=828.9 watts. OK, now let's take some empirical measurements:

3/4 HP motor FLA 11.4 amps. Running a grinder: actual watts used 362! (only load is the grinding wheel) Now let's put a heavy load on that grinder with a chunk of steel: 850 watts and that's with the steel getting to hot to hold.
So what exactly are we talking about here?
You want to put a scope on it to see the instantaneous power? Are you kidding? I'll tell you what, I have instruments here that can measure down to nanoamps, don't let me embarrass anyone with more real life tests.
And a locked rotor is not starting inertia from zero rpms, go back and read my post on how locked rotors blow fuses.

How about 3 times is all anyone needs to know.

Wrong on virtually everything:
1] Find a single phase motor with 90%. Perhaps impossible but at best extremely unlikely,
2] 11.4 X 120 = ~1400 W ~ 2 HP ... 0.75/2 = 38% efficiency. But maybe thats a hi service factor motor and the quoted amps are at its top capability. If SF 1.5 [dont think youll find higher], then motor will output 1.5 x 0.75 = 1.125HP MAX. It probably would do this at SF x FLA = 17.1A ... but to give your scenario the best credence possible lets say it puts out 1.125HP on the ~2HP wattage input represented by 11.4A. Then the motor efficiency is 1.125/2 ~ 56%,
3] Hot steel is irrelevant. Even a small piece of pre hot steel, big enuf to lean on will stop a 3/4HP grinder ... but since grinder motors start slow they dont draw hi in rush - maybe only 15A. Youre saved here, accidently,
4] Are you kidding? is a diversion. Its nice that you can measure nano A, but we can assess this close enuf with one billionth of that resolution. Lets stay on subject. Locked rotor current is the current drawn when the rotor is stationary. It occurs almost instantaneously when power is applied and subsides as the motor starts. With a hard supply Voltage such as available on AC mains, yes, the locked rotor current will blow a breaker ... eventually. Breakers will normally sustain several times their rating for at least a second. By that time the motor should be started,
4] Hard start motors such as used on compressors, washing machines, pumps, general utility, etc, pull 4x+ their FLA in the 1st instant of starting. If this resulting current is above the capability of the gen its voltage drops instantly reducing start torque, perhaps below what is needed. And at the same time reducing run torque available on any motor already running. Such motor slows a little and draws more current. In such a case its likely everything will stall.
5] 3x is not all one needs to know because some motors are employed at their HP rating and start under load. Those motors require full voltage during start. This is trivial on AC mains. A much different situation with a genny sized at 3x. NOT enuf. 4X or more is needed there or the motor does not start.
larry