PTO Generator inadequate for larger HP motors?

[xtxpete]

I'd a whole lot rather have the company say that the limit is the limit than to say you should be OK and then 10 yrs down the road the generator burns out or the well pump goes and you want to blame them for it.
I use a QC45 on the farm and it's far away got superior power supply compared to the 35kw Winco we had that was mechanical control.

 

[jwinner]

It may not be so much the specific starting load but there is another concern I did not see listed. Inductive versus capacitive versus resistive loads. My kubota lowboy manual lists different kva ratings depending on the type of load, fluorescent lights and some types of motors have a much lower rating on mine. It’s the most confusing thing to understand when it comes to sizing a generator, which is probably why I don’t understand it either.

 

[wb3czi]

An old trick to start larger electric motors is to run up a smaller (say 1hp) motor up to full speed and then switch the larger motor inline (parallel) to the running motor.
The smaller motor will actually act as a generator for a second or two assisting the generator with the surge necessary to start the larger motor.
Disconnect the "assisting" motor after the big boy starts.

My two cents worth...

 

[Chewwy]

It may not be so much the specific starting load but there is another concern I did not see listed. Inductive versus capacitive versus resistive loads. My kubota lowboy manual lists different kva ratings depending on the type of load, fluorescent lights and some types of motors have a much lower rating on mine. It’s the most confusing thing to understand when it comes to sizing a generator, which is probably why I don’t understand it either.

Motors are inductive reactance load. The current flow is not in sync with the voltage. This results in greater current flow than is expected by simply converting hp to Watts or Volt Amperes.

 

[MAX-24-Dean]

I posted a thread in Rural asking about a soft start on a well pump. In short, there was not a good solution that I was comfortable with, so I will leave it as is. I do have an Easy start for the AC, the two of these are the largest consumers.

On the pump, inrush is 42Amps @ 240, which is 10080W, and settles at about 22Amps. I have a large cistern so the well pump may only run once per week. I will also perform load management, so if I need to fill the cistern, the rest of the items will be turned off to run the pump.

Sounds like you will be using load management and a 2 pole pto generator? Don't know if that is correct?
I would stay away from a 2 pole pto generator if you have any inverter appliances, inverter washng machine, inverter refrigerator or mini splits.
Any appliance that says "DC drive" also.

The reason is when you start up any of these loads with a 2 pole (pto) generator the waveform gets distorted and any electronics will eventually suffer from the non-sinusoidal jagged waveform. Taking a little life out of them bit by bit.
Even some of the pto gen manufacturers state this and only recommend a 2 pole pto gen for motor loads and not household loads.

 

[Sawyer Rob]

Sounds like you will be using load management and a 2 pole pto generator? Don't no if that is correct?
I would stay away from a 2 pole pto generator if you have any inverter appliances, inverter washng machine, inverter refrigerator or mini splits.
Any appliance that says "DC drive" also.

The reason is when you start up any of these loads with a 2 pole (pto) generator the waveform gets distorted and any electronics will eventually suffer from the non-sinusoidal jagged waveform. Taking a little life out of them bit by bit.
Even some of the pto gen manufacturers state this and only recommend a 2 pole pto gen for motor loads and not household loads.

Most of the entire home generators sold today are 2 pole generators, So, that would have to be true for them too.

SR

 

[5030]

Most of the entire home generators sold today are 2 pole generators, So, that would have to be true for them too.

SR

If the generator has a gas engine, then it will be 2 pole. If it's diesel powered, then 4 pole because diesel engines don't make enough rpm to produce 60 hertz.

Ie: 60 Hz at 3600 rpm (gas)
60 Hz at 1800 rpm (diesel)

My Generac is 4 pole, diesel powered.

 

[Chewwy]

Bad information from you (as usual).. If the generator has a gas engine, then it will be 2 pole. If it's diesel powered, then 4 pole because diesel engines don't make enough rpm to produce 60 hertz.

Ie: 60 Hz at 3600 rpm (gas)
60 Hz at 1800 rpm (diesel)

My Generac is 4 pole, diesel powered.

This thread is about PTO generators. PTO generators have input shaft gearing to get there required rpms from the PTOs 540 RPM regardless of being gas or diesel.

 

[jwinner]

Bad information from you (as usual).. If the generator has a gas engine, then it will be 2 pole. If it's diesel powered, then 4 pole because diesel engines don't make enough rpm to produce 60 hertz.

Ie: 60 Hz at 3600 rpm (gas)
60 Hz at 1800 rpm (diesel)

My Generac is 4 pole, diesel powered.

Not entirely correct. My Kubota lowboy GL11000 is a 2-pole 3600rpm, running a D722 3-cyl diesel. I’m sure they did that to keep it as light as possible. I guess they figured the little diesel could run that fast.

So I went and looked at my manual, it says AC arc welders have a power factor of 0.4-0.6; fluorescents and mercury lamps are 0.4-0.9; incandescent lamps and electric heaters are 1.0; a “commutator motor” is 0.8-0.95; and an ”induction motor” is 0.4-0.75.

This manual is the only one I have seen break down power factor in that much detail, my 11,000 watt rating is at a power factor of 1.0, so that kind of gives me a guide to how much I need to de-rate it for a particular load, but still has a range of uncertainty.

 

[SmallChange]

DIY schemes to ameliorate the high motor starting current

[...]

make my own 3 phase

[...]

couple capacitors

[...]

adding running motors could help with subsequent motor starting loads

This is exactly what I'm talking about. But it sounds like you've done way more than I have with it. I've tinkered a little and that's it.
In industry, the inductive nature of induction motors is an expensive problem because it causes extra current to circulate in the lines. The excess is out of phase with the voltage, so it isn't power per se. However, because the lines themselves have resistance, the voltage drop along the lines IS in phase with this excess current, and so it converts real electrical power into heat in the lines. For this reason it can be worthwhile to put capacitors across motor inputs when they are running with no mechanical load (IIRC adding mechanical load brings the voltage and current back into phase so this is less of a problem). Setting up a no-load motor to run as the electrical equivalent of a flywheel, especially with such a capacitor across it, would help in starting a pump.
For some reason I decided I really wanted three phase power in my house years ago, and learned about this. But then my interests ran off someplace else before I ever made much happen. I did at one point choose 3 capacitors to put across the leads of a 1/4 hp three phase motor (yes they exist) and played with generating power with it, but the fun ended there.
I don't have the details anywhere. Sorry! But, for people who want to do this, the information is out there, it's not hard. A bit of online search turns stuff up.