PTO Generator inadequate for larger HP motors?

[Smokeydog]

Wonder how you can start a deep well pump with no load?

 

[sailonner]

I run a propane powered 5.5 KW genny when utility power goes out. My well pump is 1.5 hp single phase 230V, along with two refridgerators that might all start up together. No probelm. 2hp is usually calculated at 1500 watts. (1.5 KW) At 230VAC that's about 7 amps. Prob. about 30 amps startup for one cycle of AC inrush current (about 12 milliseconds) Usually generators of any sort are designed to factor in a startup load, and the continuous load is the name plate rating. The other factor to be concerned with is RPM on the PTO and if the genny has a link to control that by changing engine RPM

 

[Chewwy]

Wonder how you can start a deep well pump with no load?

Isolate the pump discharge from any downstream flowpath including the pressure tank. A centrifugal pump with no flow path is doing very little work compared to the work it does with an open flow path. It’s the closest one can get to no load Condition.

 

[90cummins]

A 4 pole generator has much more iron & copper and is much heavier which gives you more surge current when starting heavy loads.
90cummins

 

[Sawyer Rob]

How do you like the Winco? I’m so tempted to purchase one to run the house. Does it keep a pretty constant voltage? Thanks!

I like it very much, it easily powers my whole house, but my house isn't a house that needs a huge amount of electricity. When it's powering my house, everything runs/works just like it's on the power company's service.

When I use it when welding, you don't even know you are on a generator, same when I run the wood shop, everything works as normal.

Mines 15kw continuous, I don't need that much power, so I usually run it with my small Kubota, if I need more power, I put a bigger tractor in front of it.

SR

 

[uruiamme]

If you haven't found out after this long thread, there is a simple answer. The inrush current of a large motor is often several times more than it is rated for in continuous amps. Surely you've seen loads that are rated for one amperage, but they require a higher rated breaker? It's for stating current. It keeps them from tripping during startup.

Now, so why would this matter? Both the generator and motor are in danger of an overload. If the generator can't supply the inrush current, it will simultaneously be attempting to do so with as much current as it can. This will quickly overheat the wires and insulation inside the generator at the windings. This also simultaneously drops the voltage below the nominal (240 VAC) to the point where the same problem happens on the load side. Now, you motor has an undervoltage, which causes the inrush current to increase, overheating its windings.

Think of a curve where the two things balance out: let's say it's at 65 amps and 170 VAC. The wires are so small inside each electromechanical modern wonder that 65 amps is going to damage them quickly. And now, the motor doesn't actually start very fast, or not at all (locked rotor), and this cascades out of control. You hear, smell, and watch the two machines struggle, catch on fire, and send hot sparks toward your gas tank, your face, your fluffy dog, your trophy wife's hair, and your neighbor's Maserati convertible, all while your tractor PTO does a backflip and starts drilling a hole in the yard and using the tractor hydraulic fluid for fracking. That's when everything melts down and Chernobyl calls you to ask if they can help. Movie execs text you for the movie rights, and Elon Musk tweets you a thumbs up sign, a lightning bolt, and a skull emoji.

Ok, maybe I exaggerated a little. Get a bigger generator. Or one with protective devices that keep it from melting down.

 

[hummertom]

Just an old electrician who installed gensets for over 40 years in hospitals and nursing homes where sizing is critical. Generac makes a line , available online, 18-22 kw with 200 amp auto transfer switch (ATS) for about $8k last time I checked. Installation should be easy with a competent installer. One of my neighbors asked me to install 1 for him, 1 hr to lay it out, wait for him to do slab and dedicated propane tank, 10 hrs for installation with help from my wife. Talked to him a year later, it ran his entire house including well with no problems. Again I will repeat my previous opinion, why tie up your tractor when standby's are relatively cheap. As to fuel, from a power, cost and lifetime diesel is best, but even in mild climates you will probably need a block heater, and in my area in northern AZ a tank heater as well, gas sucks for a few reasons, mainly its useful life in most parts of the country gas is only good for about 6mos, in CA try 3 mos unless you add stabilizer, which raises the cost, and how safe is storing 100-200 gals of gas. Also gas engines tend to wear out faster, I have a friend who wore out 4 gas gensets while waiting a year for the local utility to drop his service, now he is a vet not a tech, just saying. Propane can be the best answer, starts easy even below freezing, tends to run quieter, can be stored safer, how many of us have 250gals or larger propane tanks on our place. In the case of an empty tank you can substitute a BBQ bottle for a few hrs. Lastly run PM on your genset regularly, low oil will shut it down quick.

 

[hummertom]

One more thing, with all the electrical theory mentioned in this thread I did not see any mention of K factor. With the introduction of VFD's and electronic ballasts, the Code began to address K factor about 25 yrs ago. Basically K factor will not impact homes but could in a large setting like a dairy. Diving into a little theory, if you have a basic 3 wire 120/240vac circuit, or 3 phase 4 wire circuit the neutral will carry the unbalanced load, for instance let's say you have a large barn with 2 strings of lights, one shorter than the other, 1 draws 10 amps and the other draws 15 amps, the neutral will carry the unbalanced load of 5 amps, but if these are all electronic ballasts then K factor comes into effect and the neutral can carry the ADDITIVE load of 25 amps, which would be too much for a typical #12ga Cu line. Saw this happen once, bid on a lighting job in a nursing home, wall lights in the bedrooms, typical 4 wire 3 phase run , first 3 bedrooms on A phase next on B and last on C phase all running on common neutral. General contractor outbid me by $4 dollars per bed, but he didn't know squat about electrical, I bid the job with 34watt Mag 3 magnetic ballasts ( no K factor), he bid the job with 32watt electronic ballasts (BIG K factor), was in the bldg doing a genset service when the customer came to me to explain the problem, you couldn't hold the neutral as K factor was causing the neutral to carry about 45 amps, solution, add dedicated neutral to every circuit or change fixtures, needless to say he lost his butt. Customer never again hied a general contractor to do electrical.

 

[ponytug]

...

On a slightly different question, for those with 60Amp plugs, how did you connect it to your house? I haven’t found a premade cord and manufacturers want you to buy the plug to install on #4/4 section of cord. That’s fine but what about the other end? Is it wired to the breaker or do you have an external plug?

I looked around for waterproof, locking plug/outlet combinations and came up with pin and sleeve, aka IEC 60309. They come in a wide variety of voltage, phases, and amperage. There are many different manufacturers. Hubbell, Leviton, Eaton, Scame, etc.

The also come with outlets that are only live after the plug is fully engaged in the socket.

The down side is that these connectors aren't cheap.

Here is a graphic for the possible connectors, in 30, 60 and 100A versions;

All the best,

Peter

 

[Catchthedig]

Getting back down to earth, can any of you electrical wizards tell me how to find a guy that can diagnose and maybe fix my 14kw Winpower (predecessor to Winco) pto generator ? Unit is probably 10 or more years old, 2 pole, less than 200 hours total operating time because only used for outages. I recently tried to test maximum demand (house and barn). A little blue smoke appeared near the 3-pt hitch and I shut things down. Now I get nothing at all at 540 rpm pto speed, 2200 engine rpm, 28 hp tractor pto power. Generator was made in France, don't know about gen gearbox. Everything (u-joints etc) runs smoothly, no visual evidence of overheating, gearbox oil good. Circuit breaker (60 amp) not tripped. Electrical load included some resistance heating, 240 well pump, fridge, lighting -- usual household stuff. Replacement Winco gen about $3k which is a lot more than replacing an internal diode.
Might be something as simple as that, but who can tell me?