PTO Generator inadequate for larger HP motors?

[etpm]

Just to add an option, I *think* you could make this work by getting other motors and adding them to the circuit, starting them one at a time. Even better if you add the right amount of capacitance across those motor's terminals to counter their inductance -- this is the amount of capacitance that minimizes the current draw when the motor is running at full speed with no load.
These motors will all act as flywheels to create the extra wattage it takes to start your large motor. The power grid has the same property, and this is where very short term power reserves come from (for example to handle an extra load for a second, which is way too brief to add generator capacity).

There are multiple DIY schemes to ameliorate the high motor starting current problem but I have the feeling that the OP is not interested in a DIY solution.
When I first started my machine shop in my garage over 40 years ago I had to make my own 3 phase. I bought a "Phase Converter" that was basically just a couple capacitors and a relay. A trip to a good library helped me learn about rotary phase converters and also how adding running motors could help with subsequent motor starting loads. And I used this information. But it was 40 some years ago.
It's good that you posted about this. Perhaps you could post some links or instructions on how to do this for the OP's motor load just in case the OP is interested in trying a DIY solution.
Eric

 

[hiddentacocatneddih]

Buy a pto pump and run the pump directly?

 

[LouNY]

There are multiple DIY schemes to ameliorate the high motor starting current problem but I have the feeling that the OP is not interested in a DIY solution.
When I first started my machine shop in my garage over 40 years ago I had to make my own 3 phase. I bought a "Phase Converter" that was basically just a couple capacitors and a relay. A trip to a good library helped me learn about rotary phase converters and also how adding running motors could help with subsequent motor starting loads. And I used this information. But it was 40 some years ago.
It's good that you posted about this. Perhaps you could post some links or instructions on how to do this for the OP's motor load just in case the OP is interested in trying a DIY solution.
Eric

Or, just get a slightly larger 4 pole generator.

 

[Sawyer Rob]

Or, just get a slightly larger 4 pole generator.

My 15kw Winco would start it, no problem at all, a 3hp motor is no big deal...

I've exercised my Winco by powering my shop many times, and that means starting motors in the shop, it works perfectly.

SR

 

[LouNY]

My 15kw Winco would start it, no problem at all, a 3hp motor is no big deal...

I've exercised my Winco by powering my shop many times, and that means starting motors in the shop, it works perfectly.

SR

The OP was concerned as the pto generator that he was looking a 12Kw had a warning not for starting a 3hp motor. That was a 2 pole generator. A four pole should not have any problem.

 

[Sawyer Rob]

The OP was concerned as the pto generator that he was looking a 12Kw had a warning not for starting a 3hp motor. That was a 2 pole generator. A four pole should not have any problem.

I agree, but I'm just saying that maybe a *brand switch* would be a good option for him too.

BTW, my Winco is a 2 pole also...

SR

 

[Chewwy]

Thank you for the replies. I have not bought one yet, but I’m getting very close to pulling the trigger. I like the Baumalight, but the warning may be a dealbreaker.

Here is what the response was from them, it could be a CYA statement or some deep electrical reason as mentioned above.

”The info is indeed correct & the TX series is a 2 pole unit & is not capable of handling the start up requirements of motors beyond 2 Horsepower. The KR or QC series are 4 pole winding units delivering a more consistent supply & are capable of handling such high start loads of larger motors”.

Looking at the 10KW and 16KW IMD, they’re on sale for the next week. I really like the AVR, although a Sense Flex or similar could do they same. However they don’t have surge ratings, just continuous.

I am also considering the 12k Northstar, it gets good reviews, with surge to 13kw. And the 15KW Winco.

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?

Do you know your well pumps nameplate ratings?

A 2hp induction motor may well exceed the 13,000 kW surge rating on when starting.

 

[arcteryx]

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.

 

[Vigo327]

If you think its going to void your warranty and you care about that i would just switch brands. If not i would just get it and move on with life as im ~98% certain its just going to work fine.

I suspect the issue has more to do with how far the hz will drop as the tractor adjusts to the load, than it has to do with any damage to the generator head windings. That really only matters if there are other sensitive appliances being powered at the same time.

 

[Chewwy]

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.

Typical clamp on current meters are just not capable of accurately measuring inrush current. The peak inrush is usually over before the meters start to detect it.

Your measured running load is 22 Amps. Inrush is typically around 6 times that. 132 Amps amps at 240 V is far greater than the surge rating of the Northstar generaor you were looking at.

 

[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.