PTO generator

[Rob-D]

True that, but there are some very nice inverter generators out there. The neighbor has a Honda 6000 that's very quiet. The engine doesn't have to run at a fixed speed to maintain a 60Hz line frequency, and only revs when load demands. The inverter takes care of the AC side.

There are also some significant advantages in terms of noise and efficiency.

This is why I asked about an inverter PTO generator. The tractor wouldn't have to run at an exact (high) RPM to maintain the output at 60Hz, and could _maybe_ run slower and quieter. Just speculation on my part, since I haven't seen such a beast.

This is probably OT for this discussion, though...

Z.

There is no inversion on the AC side, the Honda gas engine turns the Alternator. The inverter side (DC) is very low amperage. My Honda EU2000i runs 120v/16.7 amps AC but only 96W DC (12V x 8A).
Inverters, even very highly efficient ones still lose a few percent, this with any DC generator driver loses would have lower efficiency than an alternator brushless system. This is one reason why cars went to alternators. You can get 100 amp alternator in a car that is very small. The trick in cars is that they use the fan belt and gearing to turn the alternator very fast, that's why lights dim slightly when the car is idling. Spinning a generator at those speeds would explode the armature. Alternators run three phase, 120 degrees apart. the overlapping phases get rectified by the diodes in a delta 'Y' configuration and the battery sees a relatively smooth voltage. On the Honda EU2000i they use a small rectifier off the alternator for the 96W DC out. (small battery charging)

I'm not sure why you're talking about noise? The EU2000i is about as quiet as you can get in my view.The brushless alternator is quiet, the engine sound is all you get, that would be the same regardless whether it's inverter or direct alternator.

 

[Rob-D]

A simpler way to do it would be to use a tractor with a 1000RPM PTO throttled back so that the PTO was spinning at 540RPMs. John Deere does this with their 'ePTO' and many older tractors (such as our B7500) have a 1000RPM rear PTO setting.

Aaron Z

That's great IF the PTO HP can handle the lack of gear reduction. PTO generators run ~2600 engine speed to 540 gen speed. A PTO HP rating of 25 at 540 rpm from an engine spinning at 2600 rpms has greater torque than the same engine running at 1000 rpms with a PTO of 540. Think of your car trying to pull you up a hill from a dead stop in top gear.

 

[GPintheMitten]

Theoretically, you could gear a bicycle to have 540 rpm but I doubt you would have the horsepower in your legs to spin it. I think the same would hold true for tryin g to throttle down your tractor to get the 1000 rpm pto to spin at 540.

We are basically trying to convert gas or diesel to electricity. You have to burn enough on the input side to get the killawatts out.

 

[zoltanthegypsy]

Rob-D, I'm afraid I don't follow what you are saying. My bad. My understanding of an inverter generator is this:

Engine -> alternator -> bulk DC -> inverter -> 60Hz AC.

The small DC output you mention isn't the inverter output - inverters make AC, not DC. That "bonus" DC output either comes from the bulk DC from the alternator, or from a secondary winding specifically for that purpose.

The efficiency and noise advantages come (as I said) from not having to run the generator engine at full chat at all times just to keep the 60Hz output on freq. At full load it's possible that an inverter generator is a little less efficient than a non-inverter, but for home use, in my experience, they aren't run at full load 24/7.

Anyway OT here, methinks,
Z.

 

[lakeside]

I deployed with the Canadian military during the 1998 Ice Storm that hit Ontario and Quebec. I was lucky that my own home only lost power for 10 minutes but some folks, especially those with sump pumps and farmers who needed to water their livestock, were hurting for sometimes weeks. I bought a used Kubota 11k generator last year and although I've never had to use it, it's there. What I did learn from my years in the Army is if you don't start anything engine driven device on a regular basis, it just won't start when you need it. I run my generator once a month for about 30 minutes. Just last month I went to start the generator and all I heard was a click, humm dead battery. I did a load test and the battery was fried. Bought a new battery and all is good. I know it's too late for those in the middle of the flooding but there will be end to this/

I feel for the folks who are going through the aftermath of Sandy, there nothing so hard as to see there's absolutely nothing you can do to save your home or things like family pictures.

 

[Rob-D]

Theoretically, you could gear a bicycle to have 540 rpm but I doubt you would have the horsepower in your legs to spin it. I think the same would hold true for tryin g to throttle down your tractor to get the 1000 rpm pto to spin at 540.

We are basically trying to convert gas or diesel to electricity. You have to burn enough on the input side to get the killawatts out.

Yes, and there are specific values you can't get around. One HP = 746 watts, you can build efficient machines but you just can't beat a COP of 1.

 

[Rob-D]

Rob-D, I'm afraid I don't follow what you are saying. My bad. My understanding of an inverter generator is this:

Engine -> alternator -> bulk DC -> inverter -> 60Hz AC.

The small DC output you mention isn't the inverter output - inverters make AC, not DC. That "bonus" DC output either comes from the bulk DC from the alternator, or from a secondary winding specifically for that purpose.

The efficiency and noise advantages come (as I said) from not having to run the generator engine at full chat at all times just to keep the 60Hz output on freq. At full load it's possible that an inverter generator is a little less efficient than a non-inverter, but for home use, in my experience, they aren't run at full load 24/7.

Anyway OT here, methinks,
Z.

An inverter inverts DC to AC or AC to DC, it is, for the most part, an electronic device. A dynamo makes DC, an alternator makes AC, not DC, and a generator converts mechanical energy to electrical energy. Diodes on the phase windings of alternators rectify the AC to give a suedo DC out. Because the three phases are 120 degrees apart the diodes do a pretty good job of mimicking DC without the use of capacitors. The low voltage secondary winding of the Honda gen set is rectified AC that gives a low power DC. Alternators do not output DC, a process must follow the AC from an alternator to make DC.

 

[DarkBlack]

There is no inversion on the AC side, the Honda gas engine turns the Alternator. The inverter side (DC) is very low amperage. My Honda EU2000i runs 120v/16.7 amps AC but only 96W DC (12V x 8A).
Inverters, even very highly efficient ones still lose a few percent, this with any DC generator driver loses would have lower efficiency than an alternator brushless system. This is one reason why cars went to alternators. You can get 100 amp alternator in a car that is very small. The trick in cars is that they use the fan belt and gearing to turn the alternator very fast, that's why lights dim slightly when the car is idling. Spinning a generator at those speeds would explode the armature. Alternators run three phase, 120 degrees apart. the overlapping phases get rectified by the diodes in a delta 'Y' configuration and the battery sees a relatively smooth voltage. On the Honda EU2000i they use a small rectifier off the alternator for the 96W DC out. (small battery charging)

I'm not sure why you're talking about noise? The EU2000i is about as quiet as you can get in my view.The brushless alternator is quiet, the engine sound is all you get, that would be the same regardless whether it's inverter or direct alternator.

What are diodes in a delta "Y" configuration?

 

[DarkBlack]

An inverter inverts DC to AC or AC to DC, it is, for the most part, an electronic device. A dynamo makes DC, an alternator makes AC, not DC, and a generator converts mechanical energy to electrical energy. Diodes on the phase windings of alternators rectify the AC to give a suedo DC out. Because the three phases are 120 degrees apart the diodes do a pretty good job of mimicking DC without the use of capacitors. The low voltage secondary winding of the Honda gen set is rectified AC that gives a low power DC. Alternators do not output DC, a process must follow the AC from an alternator to make DC.

The corrrect term "inverter" applies to electronics that produces ac from dc, not the other way around.

 

[DarkBlack]

True that, but there are some very nice inverter generators out there. The neighbor has a Honda 6000 that's very quiet. The engine doesn't have to run at a fixed speed to maintain a 60Hz line frequency, and only revs when load demands. The inverter takes care of the AC side.

There are also some significant advantages in terms of noise and efficiency.

This is why I asked about an inverter PTO generator. The tractor wouldn't have to run at an exact (high) RPM to maintain the output at 60Hz, and could _maybe_ run slower and quieter. Just speculation on my part, since I haven't seen such a beast.This is probably OT for this discussion, though...

Z.

For a PTO inverter to work, the tractor's govenor would have to be somehow tied closed loop with the electric load, that would be difficult. Two posible improvements would be: 1- If a maker would make a pto genny with double the normal speed increase ratio, or even better, a selectable one, so small tractors could run normal rpm's. 2- The owner can make a pulley, or sprocket speed doubler between the pto shaft and the genny shaft, and run the tractor at half rpm's.